Add optionality to catch bindings (#634)

* Add optionality to catch bindings (plus tests)

* Update ast/spec, README, set param to null if no param with plugin optionalCatchBinding

* Fix: wrap param = null in else case

* Fix tests for optional catch binding; add tests which include finally clause

README.md

@@ -146,6 +146,7 @@ require("babylon").parse("code", {
 | `optionalChaining` ([proposal](https://github.com/tc39/proposal-optional-chaining)) | `a?.b` |
 | `importMeta` ([proposal](https://github.com/tc39/proposal-import-meta)) | `import.meta.url` |
 | `bigInt` ([proposal](https://github.com/tc39/proposal-bigint)) | `100n` |
+| `optionalCatchBinding` ([proposal](https://github.com/babel/proposals/issues/7)) | `try {throw 0;} catch{do();}` |
 
 ### FAQ
 

ast/spec.md

@@ -442,7 +442,7 @@ A `try` statement. If `handler` is `null` then `finalizer` must be a `BlockState
 ```js
 interface CatchClause <: Node {
   type: "CatchClause";
-  param: Pattern;
+  param: Pattern | null;
   body: BlockStatement;
 }
 ```

src/parser/statement.js

@@ -491,12 +491,14 @@ export default class StatementParser extends ExpressionParser {
     if (this.match(tt._catch)) {
       const clause = this.startNode();
       this.next();
-
+      if (this.match(tt.parenL) || !this.hasPlugin("optionalCatchBinding")) {
-      this.expect(tt.parenL);
+        this.expect(tt.parenL);
-      clause.param = this.parseBindingAtom();
+        clause.param = this.parseBindingAtom();
-      this.checkLVal(clause.param, true, Object.create(null), "catch clause");
+        this.checkLVal(clause.param, true, Object.create(null), "catch clause");
-      this.expect(tt.parenR);
+        this.expect(tt.parenR);
-
+      } else {
+        clause.param = null;
+      }
       clause.body = this.parseBlock();
       node.handler = this.finishNode(clause, "CatchClause");
     }

test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding-finally/actual.js

@@ -0,0 +1,9 @@
+try {
+
+}
+catch {
+
+}
+finally {
+  
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding-finally/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token, expected ( (4:6)"
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding/actual.js

@@ -0,0 +1,6 @@
+try {
+
+}
+catch {
+  
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token, expected ( (4:6)"
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding-finally/actual.js

@@ -0,0 +1,4 @@
+try {
+} catch (err) {
+} finally {
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding-finally/expected.json

@@ -0,0 +1,133 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 35,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 2,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 8,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 2
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "param": {
+            "type": "Identifier",
+            "start": 15,
+            "end": 18,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 9
+              },
+              "end": {
+                "line": 2,
+                "column": 12
+              },
+              "identifierName": "err"
+            },
+            "name": "err"
+          },
+          "body": {
+            "type": "BlockStatement",
+            "start": 20,
+            "end": 23,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 14
+              },
+              "end": {
+                "line": 3,
+                "column": 1
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": {
+          "type": "BlockStatement",
+          "start": 32,
+          "end": 35,
+          "loc": {
+            "start": {
+              "line": 3,
+              "column": 10
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding/actual.js

@@ -0,0 +1,2 @@
+try {
+} catch (err) {}

test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding/expected.json

@@ -0,0 +1,117 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 22,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 2,
+      "column": 16
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 22,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 2,
+        "column": 16
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 22,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 2,
+            "column": 16
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 2,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 8,
+          "end": 22,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 2
+            },
+            "end": {
+              "line": 2,
+              "column": 16
+            }
+          },
+          "param": {
+            "type": "Identifier",
+            "start": 15,
+            "end": 18,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 9
+              },
+              "end": {
+                "line": 2,
+                "column": 12
+              },
+              "identifierName": "err"
+            },
+            "name": "err"
+          },
+          "body": {
+            "type": "BlockStatement",
+            "start": 20,
+            "end": 22,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 14
+              },
+              "end": {
+                "line": 2,
+                "column": 16
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": null
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding-finally/actual.js

@@ -0,0 +1,9 @@
+try {
+
+}
+catch {
+
+}
+finally {
+  
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding-finally/expected.json

@@ -0,0 +1,117 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 34,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 9,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 34,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 9,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 34,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 9,
+            "column": 1
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 8,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 9,
+          "end": 19,
+          "loc": {
+            "start": {
+              "line": 4,
+              "column": 0
+            },
+            "end": {
+              "line": 6,
+              "column": 1
+            }
+          },
+          "param": null,
+          "body": {
+            "type": "BlockStatement",
+            "start": 15,
+            "end": 19,
+            "loc": {
+              "start": {
+                "line": 4,
+                "column": 6
+              },
+              "end": {
+                "line": 6,
+                "column": 1
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": {
+          "type": "BlockStatement",
+          "start": 28,
+          "end": 34,
+          "loc": {
+            "start": {
+              "line": 7,
+              "column": 8
+            },
+            "end": {
+              "line": 9,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding-finally/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalCatchBinding"]
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding/actual.js

@@ -0,0 +1,6 @@
+try {
+
+}
+catch {
+  
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding/expected.json

@@ -0,0 +1,101 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 21,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 6,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 21,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 6,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 21,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 6,
+            "column": 1
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 8,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 9,
+          "end": 21,
+          "loc": {
+            "start": {
+              "line": 4,
+              "column": 0
+            },
+            "end": {
+              "line": 6,
+              "column": 1
+            }
+          },
+          "param": null,
+          "body": {
+            "type": "BlockStatement",
+            "start": 15,
+            "end": 21,
+            "loc": {
+              "start": {
+                "line": 4,
+                "column": 6
+              },
+              "end": {
+                "line": 6,
+                "column": 1
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": null
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-no-binding/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalCatchBinding"]
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding-finally/actual.js

@@ -0,0 +1,4 @@
+try {
+} catch (err) {
+} finally {
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding-finally/expected.json

@@ -0,0 +1,133 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 35,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 2,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 8,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 2
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "param": {
+            "type": "Identifier",
+            "start": 15,
+            "end": 18,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 9
+              },
+              "end": {
+                "line": 2,
+                "column": 12
+              },
+              "identifierName": "err"
+            },
+            "name": "err"
+          },
+          "body": {
+            "type": "BlockStatement",
+            "start": 20,
+            "end": 23,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 14
+              },
+              "end": {
+                "line": 3,
+                "column": 1
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": {
+          "type": "BlockStatement",
+          "start": 32,
+          "end": 35,
+          "loc": {
+            "start": {
+              "line": 3,
+              "column": 10
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding-finally/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalCatchBinding"]
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding/actual.js

@@ -0,0 +1,2 @@
+try {
+} catch (err) {}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding/expected.json

@@ -0,0 +1,117 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 22,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 2,
+      "column": 16
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 22,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 2,
+        "column": 16
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "TryStatement",
+        "start": 0,
+        "end": 22,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 2,
+            "column": 16
+          }
+        },
+        "block": {
+          "type": "BlockStatement",
+          "start": 4,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 2,
+              "column": 1
+            }
+          },
+          "body": [],
+          "directives": []
+        },
+        "handler": {
+          "type": "CatchClause",
+          "start": 8,
+          "end": 22,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 2
+            },
+            "end": {
+              "line": 2,
+              "column": 16
+            }
+          },
+          "param": {
+            "type": "Identifier",
+            "start": 15,
+            "end": 18,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 9
+              },
+              "end": {
+                "line": 2,
+                "column": 12
+              },
+              "identifierName": "err"
+            },
+            "name": "err"
+          },
+          "body": {
+            "type": "BlockStatement",
+            "start": 20,
+            "end": 22,
+            "loc": {
+              "start": {
+                "line": 2,
+                "column": 14
+              },
+              "end": {
+                "line": 2,
+                "column": 16
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        },
+        "guardedHandlers": [],
+        "finalizer": null
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/experimental/optional-catch-binding/yes-plugin-yes-binding/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["optionalCatchBinding"]
+}