[babel 8] Disallow sequence expressions in JSX expression containers (#12447)

* jsx: fix sequence expression at JSXAttributeValue (#8787)

* jsx: fix sequence expression at JSXAttributeValue

* Change logic for detecting unparenthesized expressions

* use parseMaybeAssign instead of custom error handling

Co-authored-by: Daniel Tschinder <daniel@tschinder.de>
Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

* I'm not good at booleans

* Format

* Throw a recoverable error

Co-authored-by: Bruno Macabeus <macabeus@users.noreply.github.com>
Co-authored-by: Daniel Tschinder <daniel@tschinder.de>

packages/babel-parser/src/plugins/jsx/index.js

@@ -24,6 +24,8 @@ const JsxErrors = Object.freeze({
     "JSX attributes must only be assigned a non-empty expression",
   MissingClosingTagFragment: "Expected corresponding JSX closing tag for <>",
   MissingClosingTagElement: "Expected corresponding JSX closing tag for <%0>",
+  UnexpectedSequenceExpression:
+    "Sequence expressions cannot be directly nested inside JSX. Did you mean to wrap it in parentheses (...)?",
   UnsupportedJsxValue:
     "JSX value should be either an expression or a quoted JSX text",
   UnterminatedJsxContent: "Unterminated JSX contents",
@@ -344,9 +346,24 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       if (this.match(tt.braceR)) {
         node.expression = this.jsxParseEmptyExpression();
       } else {
-        node.expression = this.parseExpression();
+        const expression = this.parseExpression();
+
+        if (process.env.BABEL_8_BREAKING) {
+          if (
+            expression.type === "SequenceExpression" &&
+            !expression.extra?.parenthesized
+          ) {
+            this.raise(
+              expression.expressions[1].start,
+              JsxErrors.UnexpectedSequenceExpression,
+            );
+          }
+        }
+
+        node.expression = expression;
       }
       this.expect(tt.braceR);
+
       return this.finishNode(node, "JSXExpressionContainer");
     }