fix #2486, fix #3029: node re-export annotations

CHANGELOG.md

@@ -13,6 +13,35 @@
     type C = { [readonly in Foo]: number }
     ```
 
+* Add annotations for re-exported modules in node ([#2486](https://github.com/evanw/esbuild/issues/2486), [#3029](https://github.com/evanw/esbuild/issues/3029))
+
+    Node lets you import named imports from a CommonJS module using ESM import syntax. However, the allowed names aren't derived from the properties of the CommonJS module. Instead they are derived from an arbitrary syntax-only analysis of the CommonJS module's JavaScript AST.
+
+    To accommodate node doing this, esbuild's ESM-to-CommonJS conversion adds a special non-executable "annotation" for node that describes the exports that node should expose in this scenario. It takes the form `0 && (module.exports = { ... })` and comes at the end of the file (`0 && expr` means `expr` is never evaluated).
+
+    Previously esbuild didn't do this for modules re-exported using the `export * from` syntax. Annotations for these re-exports will now be added starting with this release:
+
+    ```js
+    // Original input
+    export { foo } from './foo'
+    export * from './bar'
+
+    // Old output (with --format=cjs --platform=node)
+    ...
+    0 && (module.exports = {
+      foo
+    });
+
+    // New output (with --format=cjs --platform=node)
+    ...
+    0 && (module.exports = {
+      foo,
+      ...require("./bar")
+    });
+    ```
+
+    Note that you need to specify both `--format=cjs` and `--platform=node` to get these node-specific annotations.
+
 ## 0.17.14
 
 * Allow the TypeScript 5.0 `const` modifier in object type declarations ([#3021](https://github.com/evanw/esbuild/issues/3021))

internal/bundler_tests/bundler_default_test.go

@@ -1615,6 +1615,11 @@ func TestExportWildcardFSNodeES6(t *testing.T) {
 		files: map[string]string{
 			"/entry.js": `
 				export * from 'fs'
+				export * from './internal'
+				export * from './external'
+			`,
+			"/internal.js": `
+				export let foo = 123
 			`,
 		},
 		entryPaths: []string{"/entry.js"},
@@ -1623,6 +1628,13 @@ func TestExportWildcardFSNodeES6(t *testing.T) {
 			OutputFormat:  config.FormatESModule,
 			AbsOutputFile: "/out.js",
 			Platform:      config.PlatformNode,
+			ExternalSettings: config.ExternalSettings{
+				PreResolve: config.ExternalMatchers{
+					Exact: map[string]bool{
+						"./external": true,
+					},
+				},
+			},
 		},
 	})
 }
@@ -1632,6 +1644,11 @@ func TestExportWildcardFSNodeCommonJS(t *testing.T) {
 		files: map[string]string{
 			"/entry.js": `
 				export * from 'fs'
+				export * from './internal'
+				export * from './external'
+			`,
+			"/internal.js": `
+				export let foo = 123
 			`,
 		},
 		entryPaths: []string{"/entry.js"},
@@ -1640,6 +1657,13 @@ func TestExportWildcardFSNodeCommonJS(t *testing.T) {
 			OutputFormat:  config.FormatCommonJS,
 			AbsOutputFile: "/out.js",
 			Platform:      config.PlatformNode,
+			ExternalSettings: config.ExternalSettings{
+				PreResolve: config.ExternalMatchers{
+					Exact: map[string]bool{
+						"./external": true,
+					},
+				},
+			},
 		},
 	})
 }

internal/bundler_tests/snapshots/snapshots_default.txt

@@ -1505,15 +1505,39 @@ TestExportWildcardFSNodeCommonJS
 ---------- /out.js ----------
 // entry.js
 var entry_exports = {};
+__export(entry_exports, {
+  foo: () => foo
+});
 module.exports = __toCommonJS(entry_exports);
 __reExport(entry_exports, require("fs"), module.exports);
 
+// internal.js
+var foo = 123;
+
+// entry.js
+__reExport(entry_exports, require("./external"), module.exports);
+// Annotate the CommonJS export names for ESM import in node:
+0 && (module.exports = {
+  foo,
+  ...require("fs"),
+  ...require("./external")
+});
+
 ================================================================================
 TestExportWildcardFSNodeES6
 ---------- /out.js ----------
 // entry.js
 export * from "fs";
 
+// internal.js
+var foo = 123;
+
+// entry.js
+export * from "./external";
+export {
+  foo
+};
+
 ================================================================================
 TestExportsAndModuleFormatCommonJS
 ---------- /out.js ----------

internal/linker/linker.go

@@ -4208,7 +4208,7 @@ func (c *linkerContext) generateEntryPointTailJS(
 		// of this parser, which the node project uses to detect named exports in
 		// CommonJS files: https://github.com/guybedford/cjs-module-lexer. Think of
 		// this code as an annotation for that parser.
-		if c.options.Platform == config.PlatformNode && len(repr.Meta.SortedAndFilteredExportAliases) > 0 {
+		if c.options.Platform == config.PlatformNode {
 			// Add a comment since otherwise people will surely wonder what this is.
 			// This annotation means you can do this and have it work:
 			//
@@ -4228,11 +4228,6 @@ func (c *linkerContext) generateEntryPointTailJS(
 			// instead of "__export" but support for that would need to be added to
 			// "cjs-module-lexer" and then we would need to be ok with not supporting
 			// older versions of node that don't have that newly-added support.
-			if !c.options.MinifyWhitespace {
-				stmts = append(stmts,
-					js_ast.Stmt{Data: &js_ast.SComment{Text: `// Annotate the CommonJS export names for ESM import in node:`}},
-				)
-			}
 
 			// "{a, b, if: null}"
 			var moduleExports []js_ast.Property
@@ -4259,20 +4254,38 @@ func (c *linkerContext) generateEntryPointTailJS(
 				})
 			}
 
-			// "0 && (module.exports = {a, b, if: null});"
-			expr := js_ast.Expr{Data: &js_ast.EBinary{
-				Op:   js_ast.BinOpLogicalAnd,
-				Left: js_ast.Expr{Data: &js_ast.ENumber{Value: 0}},
-				Right: js_ast.Assign(
-					js_ast.Expr{Data: &js_ast.EDot{
-						Target: js_ast.Expr{Data: &js_ast.EIdentifier{Ref: c.unboundModuleRef}},
-						Name:   "exports",
-					}},
-					js_ast.Expr{Data: &js_ast.EObject{Properties: moduleExports}},
-				),
-			}}
+			// Add annotations for re-exports: "{...require('./foo')}"
+			for _, importRecordIndex := range repr.AST.ExportStarImportRecords {
+				if record := &repr.AST.ImportRecords[importRecordIndex]; !record.SourceIndex.IsValid() {
+					moduleExports = append(moduleExports, js_ast.Property{
+						Kind:       js_ast.PropertySpread,
+						ValueOrNil: js_ast.Expr{Data: &js_ast.ERequireString{ImportRecordIndex: importRecordIndex}},
+					})
+				}
+			}
+
+			if len(moduleExports) > 0 {
+				// "0 && (module.exports = {a, b, if: null});"
+				expr := js_ast.Expr{Data: &js_ast.EBinary{
+					Op:   js_ast.BinOpLogicalAnd,
+					Left: js_ast.Expr{Data: &js_ast.ENumber{Value: 0}},
+					Right: js_ast.Assign(
+						js_ast.Expr{Data: &js_ast.EDot{
+							Target: js_ast.Expr{Data: &js_ast.EIdentifier{Ref: c.unboundModuleRef}},
+							Name:   "exports",
+						}},
+						js_ast.Expr{Data: &js_ast.EObject{Properties: moduleExports}},
+					),
+				}}
+
+				if !c.options.MinifyWhitespace {
+					stmts = append(stmts,
+						js_ast.Stmt{Data: &js_ast.SComment{Text: `// Annotate the CommonJS export names for ESM import in node:`}},
+					)
+				}
 
-			stmts = append(stmts, js_ast.Stmt{Data: &js_ast.SExpr{Value: expr}})
+				stmts = append(stmts, js_ast.Stmt{Data: &js_ast.SExpr{Value: expr}})
+			}
 		}
 
 	case config.FormatESModule:

scripts/end-to-end-tests.js

@@ -1987,6 +1987,41 @@ tests.push(
     `,
   }, { async: true }),
 
+  // https://github.com/evanw/esbuild/issues/3029
+  test([
+    'node_modules/util-ex/src/index.js',
+    'node_modules/util-ex/src/fn1.js',
+    'node_modules/util-ex/src/fn2.js',
+    '--outdir=node_modules/util-ex/lib',
+    '--format=cjs',
+    '--platform=node',
+  ], {
+    'node_modules/util-ex/src/index.js': `
+      export * from './fn1'
+      export * from './fn2'
+    `,
+    'node_modules/util-ex/src/fn1.js': `
+      export function fn1() { return 1 }
+      export default fn1
+    `,
+    'node_modules/util-ex/src/fn2.js': `
+      export function fn2() { return 2 }
+      export default fn2
+    `,
+    'node_modules/util-ex/package.json': `{
+      "main": "./lib/index.js",
+      "type": "commonjs"
+    }`,
+    'node.js': `
+      import { fn1, fn2 } from 'util-ex'
+      if (fn1() !== 1) throw 'fail 1'
+      if (fn2() !== 2) throw 'fail 2'
+    `,
+    'package.json': `{
+      "type": "module"
+    }`,
+  }),
+
   // ESM => IIFE
   test(['in.js', '--outfile=node.js', '--format=iife'], {
     'in.js': `