Preserve decorators position when printing

babel · Feb 7, 2023 · 1fb3036 · 1fb3036
1 parent 37849e1
commit 1fb3036
Show file tree

Hide file tree

Showing 9 changed files with 54 additions and 29 deletions.
diff --git a/packages/babel-generator/src/generators/classes.ts b/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) {

diff --git a/packages/babel-generator/src/generators/expressions.ts b/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;

diff --git a/packages/babel-generator/src/generators/modules.ts b/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();

diff --git a/packages/babel-generator/src/index.ts b/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;

diff --git a/packages/babel-generator/test/fixtures/decorators/export-after/input.js b/packages/babel-generator/test/fixtures/decorators/export-after/input.js
@@ -0,0 +1,2 @@
+@dec export  class A {}
+@dec export default class {}
diff --git a/packages/babel-generator/test/fixtures/decorators/export-after/output.js b/packages/babel-generator/test/fixtures/decorators/export-after/output.js
@@ -0,0 +1,4 @@
+@dec
+export class A {}
+@dec
+export default class {}
diff --git a/packages/babel-generator/test/fixtures/decorators/export-before/input.js b/packages/babel-generator/test/fixtures/decorators/export-before/input.js
@@ -0,0 +1,2 @@
+export @dec class A {}
+export default @dec class {}
diff --git a/packages/babel-generator/test/fixtures/decorators/export-before/output.js b/packages/babel-generator/test/fixtures/decorators/export-before/output.js
@@ -0,0 +1,4 @@
+export @dec
+class A {}
+export default @dec
+class {}
diff --git a/packages/babel-generator/test/fixtures/decorators/options.json b/packages/babel-generator/test/fixtures/decorators/options.json
@@ -1,4 +1,3 @@
 {
-  "plugins": [["decorators", { "decoratorsBeforeExport": false }]],
-  "decoratorsBeforeExport": true
+  "plugins": ["decorators"]
 }