Fix right precedence of Hack pipes (#13668)

packages/babel-parser/src/parser/error-message.js

@@ -134,6 +134,7 @@ export const ErrorMessages = makeErrorTemplates(
     ParamDupe: "Argument name clash.",
     PatternHasAccessor: "Object pattern can't contain getter or setter.",
     PatternHasMethod: "Object pattern can't contain methods.",
+    // This error is only used by the smart-mix proposal
     PipeBodyIsTighter:
       "Unexpected %0 after pipeline body; any %0 expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence.",
     PipeTopicRequiresHackPipes:
@@ -144,6 +145,8 @@ export const ErrorMessages = makeErrorTemplates(
       'Invalid topic token %0. In order to use %0 as a topic reference, the pipelineOperator plugin must be configured with { "proposal": "hack", "topicToken": "%0" }.',
     PipeTopicUnused:
       "Hack-style pipe body does not contain a topic reference; Hack-style pipes must use topic at least once.",
+    PipeUnparenthesizedBody:
+      "Hack-style pipe body cannot be an unparenthesized %0 expression; please wrap it in parentheses.",
 
     // Messages whose codes start with “Pipeline” or “PrimaryTopic”
     // are retained for backwards compatibility

packages/babel-parser/src/parser/expression.js

@@ -61,6 +61,13 @@ import { cloneIdentifier } from "./node";
 import type { SourceType } from "../options";
 */
 
+const invalidHackPipeBodies = new Map([
+  ["ArrowFunctionExpression", "arrow function"],
+  ["AssignmentExpression", "assignment"],
+  ["ConditionalExpression", "conditional"],
+  ["YieldExpression", "yield"],
+]);
+
 export default class ExpressionParser extends LValParser {
   // Forward-declaration: defined in statement.js
   /*::
@@ -285,28 +292,6 @@ export default class ExpressionParser extends LValParser {
       const operator = this.state.value;
       node.operator = operator;
 
-      const leftIsHackPipeExpression =
-        left.type === "BinaryExpression" &&
-        left.operator === "|>" &&
-        this.getPluginOption("pipelineOperator", "proposal") === "hack";
-
-      if (leftIsHackPipeExpression) {
-        // If the pipelinePlugin is configured to use Hack pipes,
-        // and if an assignment expression’s LHS invalidly contains `|>`,
-        // then the user likely meant to parenthesize the assignment expression.
-        // Throw a human-friendly error
-        // instead of something like 'Invalid left-hand side'.
-        // For example, `x = x |> y = #` (assuming `#` is the topic reference)
-        // groups into `x = (x |> y) = #`,
-        // and `(x |> y)` is an invalid assignment LHS.
-        // This is because Hack-style `|>` has tighter precedence than `=>`.
-        // (Unparenthesized `yield` expressions are handled
-        // in `parseHackPipeBody`,
-        // and unparenthesized `=>` expressions are handled
-        // in `checkHackPipeBodyEarlyErrors`.)
-        throw this.raise(this.state.start, Errors.PipeBodyIsTighter, operator);
-      }
-
       if (this.match(tt.eq)) {
         node.left = this.toAssignable(left, /* isLHS */ true);
         refExpressionErrors.doubleProto = -1; // reset because double __proto__ is valid in assignment expression
@@ -497,16 +482,20 @@ export default class ExpressionParser extends LValParser {
         switch (this.getPluginOption("pipelineOperator", "proposal")) {
           case "hack":
             return this.withTopicBindingContext(() => {
-              const bodyExpr = this.parseHackPipeBody(op, prec);
-              this.checkHackPipeBodyEarlyErrors(startPos);
-              return bodyExpr;
+              return this.parseHackPipeBody();
             });
 
           case "smart":
             return this.withTopicBindingContext(() => {
-              const childExpr = this.parseHackPipeBody(op, prec);
+              if (this.prodParam.hasYield && this.isContextual("yield")) {
+                throw this.raise(
+                  this.state.start,
+                  Errors.PipeBodyIsTighter,
+                  this.state.value,
+                );
+              }
               return this.parseSmartPipelineBodyInStyle(
-                childExpr,
+                this.parseExprOpBaseRightExpr(op, prec),
                 startPos,
                 startLoc,
               );
@@ -539,37 +528,25 @@ export default class ExpressionParser extends LValParser {
     );
   }
 
-  // Helper function for `parseExprOpRightExpr` for the Hack-pipe operator
-  // (and the Hack-style smart-mix pipe operator).
+  parseHackPipeBody(): N.Expression {
+    const { start } = this.state;
 
-  parseHackPipeBody(op: TokenType, prec: number): N.Expression {
-    // If the following expression is invalidly a `yield` expression,
-    // then throw a human-friendly error.
-    // A `yield` expression in a generator context (i.e., a [Yield] production)
-    // starts a YieldExpression.
-    // Outside of a generator context, any `yield` as a pipe body
-    // is considered simply an identifier.
-    // This error is checked here, before actually parsing the body expression,
-    // because `yield`’s “not allowed as identifier in generator” error
-    // would otherwise have immediately
-    // occur before the pipe body is fully parsed.
-    // (Unparenthesized assignment expressions are handled
-    // in `parseMaybeAssign`,
-    // and unparenthesized `=>` expressions are handled
-    // in `checkHackPipeBodyEarlyErrors`.)
-    const bodyIsInGeneratorContext = this.prodParam.hasYield;
-    const bodyIsYieldExpression =
-      bodyIsInGeneratorContext && this.isContextual("yield");
+    const body = this.parseMaybeAssign();
 
-    if (bodyIsYieldExpression) {
-      throw this.raise(
-        this.state.start,
-        Errors.PipeBodyIsTighter,
-        this.state.value,
+    // TODO: Check how to handle type casts in Flow and TS once they are supported
+    if (invalidHackPipeBodies.has(body.type) && !body.extra?.parenthesized) {
+      this.raise(
+        start,
+        Errors.PipeUnparenthesizedBody,
+        invalidHackPipeBodies.get(body.type),
       );
-    } else {
-      return this.parseExprOpBaseRightExpr(op, prec);
     }
+    if (!this.topicReferenceWasUsedInCurrentContext()) {
+      // A Hack pipe body must use the topic reference at least once.
+      this.raise(start, Errors.PipeTopicUnused);
+    }
+
+    return body;
   }
 
   checkExponentialAfterUnary(node: N.AwaitExpression | N.UnaryExpression) {
@@ -2738,24 +2715,7 @@ export default class ExpressionParser extends LValParser {
   // The `startPos` is the starting position of the pipe body.
 
   checkHackPipeBodyEarlyErrors(startPos: number): void {
-    // If the following token is invalidly `=>`,
-    // then throw a human-friendly error
-    // instead of something like 'Unexpected token, expected ";"'.
-    // For example, `x => x |> y => #` (assuming `#` is the topic reference)
-    // groups into `x => (x |> y) => #`,
-    // and `(x |> y) => #` is an invalid arrow function.
-    // This is because Hack-style `|>` has tighter precedence than `=>`.
-    // (Unparenthesized `yield` expressions are handled
-    // in `parseHackPipeBody`,
-    // and unparenthesized assignment expressions are handled
-    // in `parseMaybeAssign`.)
-    if (this.match(tt.arrow)) {
-      throw this.raise(
-        this.state.start,
-        Errors.PipeBodyIsTighter,
-        tt.arrow.label,
-      );
-    } else if (!this.topicReferenceWasUsedInCurrentContext()) {
+    if (!this.topicReferenceWasUsedInCurrentContext()) {
       // A Hack pipe body must use the topic reference at least once.
       this.raise(startPos, Errors.PipeTopicUnused);
     }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-arrow-function-unparenthesized/options.json

@@ -7,6 +7,5 @@
         "topicToken": "#"
       }
     ]
-  ],
-  "throws": "Unexpected => after pipeline body; any => expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:8)"
+  ]
 }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-arrow-function-unparenthesized/output.json

@@ -0,0 +1,62 @@
+{
+  "type": "File",
+  "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized arrow function expression; please wrap it in parentheses. (1:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+          "left": {
+            "type": "NumericLiteral",
+            "start":0,"end":2,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":2}},
+            "extra": {
+              "rawValue": 10,
+              "raw": "10"
+            },
+            "value": 10
+          },
+          "operator": "|>",
+          "right": {
+            "type": "ArrowFunctionExpression",
+            "start":6,"end":16,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":16}},
+            "id": null,
+            "generator": false,
+            "async": false,
+            "params": [
+              {
+                "type": "Identifier",
+                "start":6,"end":7,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":7},"identifierName":"x"},
+                "name": "x"
+              }
+            ],
+            "body": {
+              "type": "BinaryExpression",
+              "start":11,"end":16,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":16}},
+              "left": {
+                "type": "Identifier",
+                "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"x"},
+                "name": "x"
+              },
+              "operator": "+",
+              "right": {
+                "type": "TopicReference",
+                "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+              }
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-logical-and/options.json

@@ -7,6 +7,5 @@
         "topicToken": "#"
       }
     ]
-  ],
-  "throws": "Unexpected &&= after pipeline body; any &&= expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:11)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-logical-and/output.json

@@ -0,0 +1,44 @@
+{
+  "type": "File",
+  "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":16,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":16}},
+            "operator": "&&=",
+            "left": {
+              "type": "Identifier",
+              "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"x"},
+              "name": "x"
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-normal/options.json

@@ -7,6 +7,5 @@
         "topicToken": "#"
       }
     ]
-  ],
-  "throws": "Unexpected = after pipeline body; any = expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:16)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-normal/output.json

@@ -0,0 +1,55 @@
+{
+  "type": "File",
+  "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":19,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":19}},
+            "operator": "=",
+            "left": {
+              "type": "ArrayPattern",
+              "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+              "elements": [
+                {
+                  "type": "Identifier",
+                  "start":10,"end":11,"loc":{"start":{"line":1,"column":10},"end":{"line":1,"column":11},"identifierName":"x"},
+                  "name": "x"
+                },
+                {
+                  "type": "Identifier",
+                  "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14},"identifierName":"y"},
+                  "name": "y"
+                }
+              ]
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":18,"end":19,"loc":{"start":{"line":1,"column":18},"end":{"line":1,"column":19}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-plus/options.json

@@ -7,6 +7,5 @@
         "topicToken": "#"
       }
     ]
-  ],
-  "throws": "Unexpected += after pipeline body; any += expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:11)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-assignment-plus/output.json

@@ -0,0 +1,44 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+            "operator": "+=",
+            "left": {
+              "type": "Identifier",
+              "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"x"},
+              "name": "x"
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-associativity/input.js

@@ -0,0 +1 @@
+1 |> f(#) |> g(#);

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-associativity/output.json

@@ -0,0 +1,66 @@
+{
+  "type": "File",
+  "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+          "left": {
+            "type": "NumericLiteral",
+            "start":0,"end":1,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":1}},
+            "extra": {
+              "rawValue": 1,
+              "raw": "1"
+            },
+            "value": 1
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":5,"end":17,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":17}},
+            "left": {
+              "type": "CallExpression",
+              "start":5,"end":9,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":9}},
+              "callee": {
+                "type": "Identifier",
+                "start":5,"end":6,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":6},"identifierName":"f"},
+                "name": "f"
+              },
+              "arguments": [
+                {
+                  "type": "TopicReference",
+                  "start":7,"end":8,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":8}}
+                }
+              ]
+            },
+            "operator": "|>",
+            "right": {
+              "type": "CallExpression",
+              "start":13,"end":17,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
+              "callee": {
+                "type": "Identifier",
+                "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14},"identifierName":"g"},
+                "name": "g"
+              },
+              "arguments": [
+                {
+                  "type": "TopicReference",
+                  "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+                }
+              ]
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-generator-yield-unparenthesized/options.json

@@ -1,4 +0,0 @@
-{
-  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "#" }]],
-  "throws": "Unexpected yield after pipeline body; any yield expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (2:14)"
-}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-nested-pipelines-with-arrow-function-with-required-topics/output.json

@@ -22,10 +22,6 @@
           "right": {
             "type": "ArrowFunctionExpression",
             "start":6,"end":32,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":32}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "id": null,
             "generator": false,
             "async": false,
@@ -40,14 +36,14 @@
               "type": "BinaryExpression",
               "start":11,"end":32,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":32}},
               "left": {
+                "type": "TopicReference",
+                "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12}}
+              },
+              "operator": "|>",
+              "right": {
                 "type": "BinaryExpression",
-                "start":11,"end":23,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":23}},
+                "start":16,"end":32,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":32}},
                 "left": {
-                  "type": "TopicReference",
-                  "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12}}
-                },
-                "operator": "|>",
-                "right": {
                   "type": "CallExpression",
                   "start":16,"end":23,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":23}},
                   "callee": {
@@ -66,27 +62,31 @@
                       "name": "$"
                     }
                   ]
-                }
-              },
-              "operator": "|>",
-              "right": {
-                "type": "BinaryExpression",
-                "start":27,"end":32,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":32}},
-                "left": {
-                  "type": "TopicReference",
-                  "start":27,"end":28,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":28}}
                 },
-                "operator": ">",
+                "operator": "|>",
                 "right": {
-                  "type": "NumericLiteral",
-                  "start":31,"end":32,"loc":{"start":{"line":1,"column":31},"end":{"line":1,"column":32}},
-                  "extra": {
-                    "rawValue": 1,
-                    "raw": "1"
+                  "type": "BinaryExpression",
+                  "start":27,"end":32,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":32}},
+                  "left": {
+                    "type": "TopicReference",
+                    "start":27,"end":28,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":28}}
                   },
-                  "value": 1
+                  "operator": ">",
+                  "right": {
+                    "type": "NumericLiteral",
+                    "start":31,"end":32,"loc":{"start":{"line":1,"column":31},"end":{"line":1,"column":32}},
+                    "extra": {
+                      "rawValue": 1,
+                      "raw": "1"
+                    },
+                    "value": 1
+                  }
                 }
               }
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-nested-pipelines-with-arrow-function-without-outer-topic/output.json

@@ -25,10 +25,6 @@
           "right": {
             "type": "ArrowFunctionExpression",
             "start":6,"end":17,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":17}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "id": null,
             "generator": false,
             "async": false,
@@ -52,6 +48,10 @@
                 "type": "TopicReference",
                 "start":16,"end":17,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":17}}
               }
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-nested-pipelines-without-outer-topic/output.json

@@ -26,10 +26,6 @@
           "right": {
             "type": "BinaryExpression",
             "start":6,"end":12,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":12}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "left": {
               "type": "Identifier",
               "start":6,"end":7,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":7},"identifierName":"$"},
@@ -40,6 +36,10 @@
               "type": "Identifier",
               "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"f"},
               "name": "f"
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-generator-parenthesized/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "#" }]]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-generator-unparenthesized/options.json

@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    [
+      "pipelineOperator",
+      {
+        "proposal": "hack",
+        "topicToken": "#"
+      }
+    ]
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-generator-unparenthesized/output.json

@@ -0,0 +1,64 @@
+{
+  "type": "File",
+  "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized yield expression; please wrap it in parentheses. (2:14)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "FunctionDeclaration",
+        "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"f"},
+          "name": "f"
+        },
+        "generator": true,
+        "async": false,
+        "params": [
+          {
+            "type": "Identifier",
+            "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15},"identifierName":"x"},
+            "name": "x"
+          }
+        ],
+        "body": {
+          "type": "BlockStatement",
+          "start":17,"end":43,"loc":{"start":{"line":1,"column":17},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ReturnStatement",
+              "start":21,"end":41,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":22}},
+              "argument": {
+                "type": "BinaryExpression",
+                "start":28,"end":40,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":21}},
+                "left": {
+                  "type": "Identifier",
+                  "start":28,"end":29,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":10},"identifierName":"x"},
+                  "name": "x"
+                },
+                "operator": "|>",
+                "right": {
+                  "type": "YieldExpression",
+                  "start":33,"end":40,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":21}},
+                  "delegate": false,
+                  "argument": {
+                    "type": "TopicReference",
+                    "start":39,"end":40,"loc":{"start":{"line":2,"column":20},"end":{"line":2,"column":21}}
+                  }
+                }
+              }
+            }
+          ],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-identifier-unparenthesized/input.js

@@ -0,0 +1 @@
+x |> yield + #;

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-identifier-unparenthesized/options.json

@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    [
+      "pipelineOperator",
+      {
+        "proposal": "hack",
+        "topicToken": "#"
+      }
+    ]
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-hash-proposal-yield-identifier-unparenthesized/output.json

@@ -0,0 +1,41 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":14,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":14}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":1,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":1},"identifierName":"x"},
+            "name": "x"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":5,"end":14,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":14}},
+            "left": {
+              "type": "Identifier",
+              "start":5,"end":10,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":10},"identifierName":"yield"},
+              "name": "yield"
+            },
+            "operator": "+",
+            "right": {
+              "type": "TopicReference",
+              "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-arrow-function-unparenthesized/options.json

@@ -7,6 +7,5 @@
         "topicToken": "%"
       }
     ]
-  ],
-  "throws": "Unexpected => after pipeline body; any => expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:8)"
+  ]
 }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-arrow-function-unparenthesized/output.json

@@ -0,0 +1,62 @@
+{
+  "type": "File",
+  "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized arrow function expression; please wrap it in parentheses. (1:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+          "left": {
+            "type": "NumericLiteral",
+            "start":0,"end":2,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":2}},
+            "extra": {
+              "rawValue": 10,
+              "raw": "10"
+            },
+            "value": 10
+          },
+          "operator": "|>",
+          "right": {
+            "type": "ArrowFunctionExpression",
+            "start":6,"end":16,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":16}},
+            "id": null,
+            "generator": false,
+            "async": false,
+            "params": [
+              {
+                "type": "Identifier",
+                "start":6,"end":7,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":7},"identifierName":"x"},
+                "name": "x"
+              }
+            ],
+            "body": {
+              "type": "BinaryExpression",
+              "start":11,"end":16,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":16}},
+              "left": {
+                "type": "Identifier",
+                "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"x"},
+                "name": "x"
+              },
+              "operator": "+",
+              "right": {
+                "type": "TopicReference",
+                "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+              }
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-logical-and/options.json

@@ -7,6 +7,5 @@
         "topicToken": "%"
       }
     ]
-  ],
-  "throws": "Unexpected &&= after pipeline body; any &&= expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:11)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-logical-and/output.json

@@ -0,0 +1,44 @@
+{
+  "type": "File",
+  "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":16,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":16}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":16,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":16}},
+            "operator": "&&=",
+            "left": {
+              "type": "Identifier",
+              "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"x"},
+              "name": "x"
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-normal/options.json

@@ -7,6 +7,5 @@
         "topicToken": "%"
       }
     ]
-  ],
-  "throws": "Unexpected = after pipeline body; any = expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:16)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-normal/output.json

@@ -0,0 +1,55 @@
+{
+  "type": "File",
+  "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":19,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":19}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":19,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":19}},
+            "operator": "=",
+            "left": {
+              "type": "ArrayPattern",
+              "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+              "elements": [
+                {
+                  "type": "Identifier",
+                  "start":10,"end":11,"loc":{"start":{"line":1,"column":10},"end":{"line":1,"column":11},"identifierName":"x"},
+                  "name": "x"
+                },
+                {
+                  "type": "Identifier",
+                  "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14},"identifierName":"y"},
+                  "name": "y"
+                }
+              ]
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":18,"end":19,"loc":{"start":{"line":1,"column":18},"end":{"line":1,"column":19}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-plus/options.json

@@ -7,6 +7,5 @@
         "topicToken": "%"
       }
     ]
-  ],
-  "throws": "Unexpected += after pipeline body; any += expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (1:11)"
-}
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-assignment-plus/output.json

@@ -0,0 +1,44 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized assignment expression; please wrap it in parentheses. (1:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"value"},
+            "name": "value"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "AssignmentExpression",
+            "start":9,"end":15,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":15}},
+            "operator": "+=",
+            "left": {
+              "type": "Identifier",
+              "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"x"},
+              "name": "x"
+            },
+            "right": {
+              "type": "TopicReference",
+              "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-associativity/input.js

@@ -0,0 +1 @@
+1 |> f(%) |> g(%);

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-associativity/output.json

@@ -0,0 +1,66 @@
+{
+  "type": "File",
+  "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":17}},
+          "left": {
+            "type": "NumericLiteral",
+            "start":0,"end":1,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":1}},
+            "extra": {
+              "rawValue": 1,
+              "raw": "1"
+            },
+            "value": 1
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":5,"end":17,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":17}},
+            "left": {
+              "type": "CallExpression",
+              "start":5,"end":9,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":9}},
+              "callee": {
+                "type": "Identifier",
+                "start":5,"end":6,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":6},"identifierName":"f"},
+                "name": "f"
+              },
+              "arguments": [
+                {
+                  "type": "TopicReference",
+                  "start":7,"end":8,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":8}}
+                }
+              ]
+            },
+            "operator": "|>",
+            "right": {
+              "type": "CallExpression",
+              "start":13,"end":17,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":17}},
+              "callee": {
+                "type": "Identifier",
+                "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14},"identifierName":"g"},
+                "name": "g"
+              },
+              "arguments": [
+                {
+                  "type": "TopicReference",
+                  "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16}}
+                }
+              ]
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-generator-yield-unparenthesized/options.json

@@ -1,4 +0,0 @@
-{
-  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "%" }]],
-  "throws": "Unexpected yield after pipeline body; any yield expression acting as Hack-style pipe body must be parenthesized due to its loose operator precedence. (2:14)"
-}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-nested-pipelines-with-arrow-function-with-required-topics/output.json

@@ -22,10 +22,6 @@
           "right": {
             "type": "ArrowFunctionExpression",
             "start":6,"end":32,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":32}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "id": null,
             "generator": false,
             "async": false,
@@ -40,14 +36,14 @@
               "type": "BinaryExpression",
               "start":11,"end":32,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":32}},
               "left": {
+                "type": "TopicReference",
+                "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12}}
+              },
+              "operator": "|>",
+              "right": {
                 "type": "BinaryExpression",
-                "start":11,"end":23,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":23}},
+                "start":16,"end":32,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":32}},
                 "left": {
-                  "type": "TopicReference",
-                  "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12}}
-                },
-                "operator": "|>",
-                "right": {
                   "type": "CallExpression",
                   "start":16,"end":23,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":23}},
                   "callee": {
@@ -66,27 +62,31 @@
                       "name": "$"
                     }
                   ]
-                }
-              },
-              "operator": "|>",
-              "right": {
-                "type": "BinaryExpression",
-                "start":27,"end":32,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":32}},
-                "left": {
-                  "type": "TopicReference",
-                  "start":27,"end":28,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":28}}
                 },
-                "operator": ">",
+                "operator": "|>",
                 "right": {
-                  "type": "NumericLiteral",
-                  "start":31,"end":32,"loc":{"start":{"line":1,"column":31},"end":{"line":1,"column":32}},
-                  "extra": {
-                    "rawValue": 1,
-                    "raw": "1"
+                  "type": "BinaryExpression",
+                  "start":27,"end":32,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":32}},
+                  "left": {
+                    "type": "TopicReference",
+                    "start":27,"end":28,"loc":{"start":{"line":1,"column":27},"end":{"line":1,"column":28}}
                   },
-                  "value": 1
+                  "operator": ">",
+                  "right": {
+                    "type": "NumericLiteral",
+                    "start":31,"end":32,"loc":{"start":{"line":1,"column":31},"end":{"line":1,"column":32}},
+                    "extra": {
+                      "rawValue": 1,
+                      "raw": "1"
+                    },
+                    "value": 1
+                  }
                 }
               }
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-nested-pipelines-with-arrow-function-without-outer-topic/output.json

@@ -25,10 +25,6 @@
           "right": {
             "type": "ArrowFunctionExpression",
             "start":6,"end":17,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":17}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "id": null,
             "generator": false,
             "async": false,
@@ -52,6 +48,10 @@
                 "type": "TopicReference",
                 "start":16,"end":17,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":17}}
               }
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-nested-pipelines-without-outer-topic/output.json

@@ -26,10 +26,6 @@
           "right": {
             "type": "BinaryExpression",
             "start":6,"end":12,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":12}},
-            "extra": {
-              "parenthesized": true,
-              "parenStart": 5
-            },
             "left": {
               "type": "Identifier",
               "start":6,"end":7,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":7},"identifierName":"$"},
@@ -40,6 +36,10 @@
               "type": "Identifier",
               "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"f"},
               "name": "f"
+            },
+            "extra": {
+              "parenthesized": true,
+              "parenStart": 5
             }
           }
         }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-generator-parenthesized/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "hack", "topicToken": "%" }]]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-generator-unparenthesized/options.json

@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    [
+      "pipelineOperator",
+      {
+        "proposal": "hack",
+        "topicToken": "%"
+      }
+    ]
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-generator-unparenthesized/output.json

@@ -0,0 +1,64 @@
+{
+  "type": "File",
+  "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Hack-style pipe body cannot be an unparenthesized yield expression; please wrap it in parentheses. (2:14)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "FunctionDeclaration",
+        "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":11,"end":12,"loc":{"start":{"line":1,"column":11},"end":{"line":1,"column":12},"identifierName":"f"},
+          "name": "f"
+        },
+        "generator": true,
+        "async": false,
+        "params": [
+          {
+            "type": "Identifier",
+            "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15},"identifierName":"x"},
+            "name": "x"
+          }
+        ],
+        "body": {
+          "type": "BlockStatement",
+          "start":17,"end":43,"loc":{"start":{"line":1,"column":17},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ReturnStatement",
+              "start":21,"end":41,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":22}},
+              "argument": {
+                "type": "BinaryExpression",
+                "start":28,"end":40,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":21}},
+                "left": {
+                  "type": "Identifier",
+                  "start":28,"end":29,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":10},"identifierName":"x"},
+                  "name": "x"
+                },
+                "operator": "|>",
+                "right": {
+                  "type": "YieldExpression",
+                  "start":33,"end":40,"loc":{"start":{"line":2,"column":14},"end":{"line":2,"column":21}},
+                  "delegate": false,
+                  "argument": {
+                    "type": "TopicReference",
+                    "start":39,"end":40,"loc":{"start":{"line":2,"column":20},"end":{"line":2,"column":21}}
+                  }
+                }
+              }
+            }
+          ],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-identifier-unparenthesized/input.js

@@ -0,0 +1 @@
+x |> yield + %;

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-identifier-unparenthesized/options.json

@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    [
+      "pipelineOperator",
+      {
+        "proposal": "hack",
+        "topicToken": "%"
+      }
+    ]
+  ]
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/hack-percent-proposal-yield-identifier-unparenthesized/output.json

@@ -0,0 +1,41 @@
+{
+  "type": "File",
+  "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":14,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":14}},
+          "left": {
+            "type": "Identifier",
+            "start":0,"end":1,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":1},"identifierName":"x"},
+            "name": "x"
+          },
+          "operator": "|>",
+          "right": {
+            "type": "BinaryExpression",
+            "start":5,"end":14,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":14}},
+            "left": {
+              "type": "Identifier",
+              "start":5,"end":10,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":10},"identifierName":"yield"},
+              "name": "yield"
+            },
+            "operator": "+",
+            "right": {
+              "type": "TopicReference",
+              "start":13,"end":14,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":14}}
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}