Implement decorators as presented at 2023-01 TC39 meeting (#15405)

Makefile

@@ -1,6 +1,6 @@
-FLOW_COMMIT = 92bbb5e9dacb8185aa73ea343954d0434b42c40b
-TEST262_COMMIT = a29788dd5d4d7664478985928e82f2a1cd7fb37d
-TYPESCRIPT_COMMIT = ce85d647ef88183c019588bcf398320ce29b625a
+FLOW_COMMIT = 105ad30f566f401db9cafcb49cd2831fb29e87c5
+TEST262_COMMIT = 76a14bf659be962dd0efa694c4f9fc12f159f774
+TYPESCRIPT_COMMIT = d87d0adcd30ac285393bf3bfbbb4d94d50c4f3c9
 
 # Fix color output until TravisCI fixes https://github.com/travis-ci/travis-ci/issues/7967
 export FORCE_COLOR = true
@@ -177,15 +177,16 @@ test-test262-update-allowlist:
 
 
 new-version-checklist:
-       # @echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
-       # @echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
-       # @echo "!!!!!!                                                   !!!!!!"
-       # @echo "!!!!!! Add any message here, and UNCOMMENT THESE LINES!  !!!!!!"
-       # @echo "!!!!!!                                                   !!!!!!"
-       # @echo "!!!!!!                                                   !!!!!!"
-       # @echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
-       # @echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
-       # @exit 1
+	@echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+	@echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+	@echo "!!!!!!                                                   !!!!!!"
+	@echo "!!!!!! Update the version to 7.21.0 in the applyDecs2301 !!!!!!"
+	@echo "!!!!!! helper, and in the assertVersion call for 2023-01 !!!!!!"
+	@echo "!!!!!! in transformer-2023-01.ts                         !!!!!!"
+	@echo "!!!!!!                                                   !!!!!!"
+	@echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+	@echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+	@exit 1
 
 new-version:
 	$(MAKE) new-version-checklist

packages/babel-generator/src/generators/classes.ts

@@ -11,15 +11,16 @@ export function ClassDeclaration(
   node: t.ClassDeclaration,
   parent: t.Node,
 ) {
-  if (process.env.BABEL_8_BREAKING) {
+  const inExport =
+    isExportDefaultDeclaration(parent) || isExportNamedDeclaration(parent);
+
+  if (
+    !inExport ||
+    !this._shouldPrintDecoratorsBeforeExport(
+      parent as t.ExportDeclaration & { declaration: t.ClassDeclaration },
+    )
+  ) {
     this.printJoin(node.decorators, node);
-  } else {
-    if (
-      !this.format.decoratorsBeforeExport ||
-      (!isExportDefaultDeclaration(parent) && !isExportNamedDeclaration(parent))
-    ) {
-      this.printJoin(node.decorators, node);
-    }
   }
 
   if (node.declare) {

packages/babel-generator/src/generators/expressions.ts

@@ -140,6 +140,18 @@ function shouldParenthesizeDecoratorExpression(
   );
 }
 
+export function _shouldPrintDecoratorsBeforeExport(
+  this: Printer,
+  node: t.ExportDeclaration & { declaration: t.ClassDeclaration },
+) {
+  if (typeof this.format.decoratorsBeforeExport === "boolean") {
+    return this.format.decoratorsBeforeExport;
+  }
+  return (
+    typeof node.start === "number" && node.start === node.declaration.start
+  );
+}
+
 export function Decorator(this: Printer, node: t.Decorator) {
   this.token("@");
   const { expression } = node;

packages/babel-generator/src/generators/modules.ts

@@ -106,18 +106,25 @@ export function ExportAllDeclaration(
   this.semicolon();
 }
 
+function maybePrintDecoratorsBeforeExport(
+  printer: Printer,
+  node: t.ExportNamedDeclaration | t.ExportDefaultDeclaration,
+) {
+  if (
+    isClassDeclaration(node.declaration) &&
+    printer._shouldPrintDecoratorsBeforeExport(
+      node as t.ExportNamedDeclaration & { declaration: t.ClassDeclaration },
+    )
+  ) {
+    printer.printJoin(node.declaration.decorators, node);
+  }
+}
+
 export function ExportNamedDeclaration(
   this: Printer,
   node: t.ExportNamedDeclaration,
 ) {
-  if (!process.env.BABEL_8_BREAKING) {
-    if (
-      this.format.decoratorsBeforeExport &&
-      isClassDeclaration(node.declaration)
-    ) {
-      this.printJoin(node.declaration.decorators, node);
-    }
-  }
+  maybePrintDecoratorsBeforeExport(this, node);
 
   this.word("export");
   this.space();
@@ -183,14 +190,7 @@ export function ExportDefaultDeclaration(
   this: Printer,
   node: t.ExportDefaultDeclaration,
 ) {
-  if (!process.env.BABEL_8_BREAKING) {
-    if (
-      this.format.decoratorsBeforeExport &&
-      isClassDeclaration(node.declaration)
-    ) {
-      this.printJoin(node.declaration.decorators, node);
-    }
-  }
+  maybePrintDecoratorsBeforeExport(this, node);
 
   this.word("export");
   this.noIndentInnerCommentsHere();

packages/babel-generator/src/index.ts

@@ -76,7 +76,7 @@ function normalizeOptions(
   };
 
   if (!process.env.BABEL_8_BREAKING) {
-    format.decoratorsBeforeExport = !!opts.decoratorsBeforeExport;
+    format.decoratorsBeforeExport = opts.decoratorsBeforeExport;
     format.jsonCompatibleStrings = opts.jsonCompatibleStrings;
   }
 
@@ -200,8 +200,9 @@ export interface GeneratorOptions {
   jsonCompatibleStrings?: boolean;
 
   /**
-   * Set to true to enable support for experimental decorators syntax before module exports.
-   * Defaults to `false`.
+   * Set to true to enable support for experimental decorators syntax before
+   * module exports. If not specified, decorators will be printed in the same
+   * position as they were in the input source code.
    * @deprecated Removed in Babel 8
    */
   decoratorsBeforeExport?: boolean;

packages/babel-generator/test/fixtures/comments/decorators-after-export-to-after/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["decorators"],
+  "decoratorsBeforeExport": false
+}

packages/babel-generator/test/fixtures/comments/decorators-after-export-to-before/input.js

@@ -0,0 +1,5 @@
+/* 1 */ export /* 2 */ @dec1 /* 3 */ @dec2
+/* 4 */ class /* 5 */ C /* 6 */ { /* 7 */ } /* 8 */
+
+/* A */ export /* B */ default /* C */ @dec1 /* D */ @dec2
+/* E */ class /* F */ { /* G */ } /* H */

packages/babel-generator/test/fixtures/comments/decorators-after-export-to-before/options.json

@@ -0,0 +1,5 @@
+{
+  "BABEL_8_BREAKING": false,
+  "plugins": ["decorators"],
+  "decoratorsBeforeExport": true
+}

packages/babel-generator/test/fixtures/comments/decorators-after-export-to-before/output.js

@@ -0,0 +1,9 @@
+/* 1 */@dec1
+/* 3 */@dec2
+/* 4 */export /* 2 */class /* 5 */C /* 6 */ {/* 7 */} /* 8 */
+
+/* A */
+@dec1
+/* D */@dec2
+/* E */export /* B */
+default /* C */class /* F */{/* G */} /* H */

packages/babel-generator/test/fixtures/comments/decorators-before-export-to-after/options.json

@@ -0,0 +1,5 @@
+{
+  "BABEL_8_BREAKING": false,
+  "plugins": ["decorators"],
+  "decoratorsBeforeExport": false
+}

packages/babel-generator/test/fixtures/comments/decorators-before-export-to-after/output.js

@@ -0,0 +1,9 @@
+/* 1 */export /* 4 */@dec1
+/* 2 */@dec2
+/* 3 */class /* 5 */C /* 6 */ {/* 7 */} /* 8 */
+
+/* A */
+export
+/* D */ default /* E */@dec1
+/* B */@dec2
+/* C */class /* F */{/* G */} /* H */

packages/babel-generator/test/fixtures/comments/decorators-before-export-to-before/input.js

@@ -0,0 +1,5 @@
+/* 1 */ @dec1 /* 2 */ @dec2 /* 3 */
+export /* 4 */ class /* 5 */ C /* 6 */ { /* 7 */ } /* 8 */
+
+/* A */ @dec1 /* B */ @dec2 /* C */
+export /* D */ default /* E */ class /* F */ { /* G */ } /* H */

packages/babel-generator/test/fixtures/comments/decorators-before-export-to-before/options.json

@@ -0,0 +1,5 @@
+{
+  "BABEL_8_BREAKING": false,
+  "plugins": ["decorators"],
+  "decoratorsBeforeExport": true
+}

packages/babel-generator/test/fixtures/decorators/export-after/input.js

@@ -0,0 +1,2 @@
+@dec export  class A {}
+@dec export default class {}

packages/babel-generator/test/fixtures/decorators/export-after/output.js

@@ -0,0 +1,4 @@
+@dec
+export class A {}
+@dec
+export default class {}

packages/babel-generator/test/fixtures/decorators/export-before/input.js

@@ -0,0 +1,2 @@
+export @dec class A {}
+export default @dec class {}

packages/babel-generator/test/fixtures/decorators/export-before/output.js

@@ -0,0 +1,4 @@
+export @dec
+class A {}
+export default @dec
+class {}

packages/babel-generator/test/fixtures/decorators/options.json

@@ -1,4 +1,3 @@
 {
-  "plugins": [["decorators", { "decoratorsBeforeExport": false }]],
-  "decoratorsBeforeExport": true
+  "plugins": ["decorators"]
 }