fix #3199: keep names + namespace + export class

CHANGELOG.md

@@ -1,5 +1,35 @@
 # Changelog
 
+## Unreleased
+
+* Fix a TypeScript code generation edge case ([#3199](https://github.com/evanw/esbuild/issues/3199))
+
+    This release fixes a regression in version 0.18.4 where using a TypeScript `namespace` that exports a `class` declaration combined with `--keep-names` and a `--target` of `es2021` or earlier could cause esbuild to export the class from the namespace using an incorrect name (notice the assignment to `X2._Y` vs. `X2.Y`):
+
+    ```ts
+    // Original code
+
+    // Old output (with --keep-names --target=es2021)
+    var X;
+    ((X2) => {
+      const _Y = class _Y {
+      };
+      __name(_Y, "Y");
+      let Y = _Y;
+      X2._Y = _Y;
+    })(X || (X = {}));
+
+    // New output (with --keep-names --target=es2021)
+    var X;
+    ((X2) => {
+      const _Y = class _Y {
+      };
+      __name(_Y, "Y");
+      let Y = _Y;
+      X2.Y = _Y;
+    })(X || (X = {}));
+    ```
+
 ## 0.18.10
 
 * Fix a tree-shaking bug that removed side effects ([#3195](https://github.com/evanw/esbuild/issues/3195))

internal/bundler_tests/bundler_ts_test.go

@@ -423,6 +423,47 @@ func TestTSExportNamespace(t *testing.T) {
 	})
 }
 
+func TestTSNamespaceKeepNames(t *testing.T) {
+	ts_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.ts": `
+				namespace ns {
+					export let foo = () => {}
+					export function bar() {}
+					export class Baz {}
+				}
+			`,
+		},
+		entryPaths: []string{"/entry.ts"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			AbsOutputFile: "/out.js",
+			KeepNames:     true,
+		},
+	})
+}
+
+func TestTSNamespaceKeepNamesTargetES2015(t *testing.T) {
+	ts_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.ts": `
+				namespace ns {
+					export let foo = () => {}
+					export function bar() {}
+					export class Baz {}
+				}
+			`,
+		},
+		entryPaths: []string{"/entry.ts"},
+		options: config.Options{
+			Mode:                  config.ModeBundle,
+			AbsOutputFile:         "/out.js",
+			KeepNames:             true,
+			UnsupportedJSFeatures: es(2015),
+		},
+	})
+}
+
 func TestTSMinifyEnum(t *testing.T) {
 	ts_suite.expectBundled(t, bundled{
 		files: map[string]string{

internal/bundler_tests/snapshots/snapshots_ts.txt

@@ -1610,6 +1610,45 @@ function foo(){let u;return(n=>(n[n.A=0]="A",n[n.B=1]="B",n[n.C=n]="C"))(u||(u={
 ---------- /b.js ----------
 export function foo(){let e;return(n=>(n[n.X=0]="X",n[n.Y=1]="Y",n[n.Z=n]="Z"))(e||(e={})),e}
 
+================================================================================
+TestTSNamespaceKeepNames
+---------- /out.js ----------
+// entry.ts
+var ns;
+((ns2) => {
+  ns2.foo = /* @__PURE__ */ __name(() => {
+  }, "foo");
+  function bar() {
+  }
+  ns2.bar = bar;
+  __name(bar, "bar");
+  class Baz {
+    static {
+      __name(this, "Baz");
+    }
+  }
+  ns2.Baz = Baz;
+})(ns || (ns = {}));
+
+================================================================================
+TestTSNamespaceKeepNamesTargetES2015
+---------- /out.js ----------
+// entry.ts
+var ns;
+((ns2) => {
+  ns2.foo = /* @__PURE__ */ __name(() => {
+  }, "foo");
+  function bar() {
+  }
+  ns2.bar = bar;
+  __name(bar, "bar");
+  const _Baz = class _Baz {
+  };
+  __name(_Baz, "Baz");
+  let Baz = _Baz;
+  ns2.Baz = _Baz;
+})(ns || (ns = {}));
+
 ================================================================================
 TestTSPreferJSOverTSInsideNodeModules
 ---------- /out/main.js ----------

internal/js_parser/js_parser.go

@@ -10617,8 +10617,10 @@ func (p *parser) visitAndAppendStmt(stmts []js_ast.Stmt, stmt js_ast.Stmt) []js_
 		result := p.visitClass(stmt.Loc, &s.Class, js_ast.InvalidRef, "")
 
 		// Remove the export flag inside a namespace
+		var nameToExport string
 		wasExportInsideNamespace := s.IsExport && p.enclosingNamespaceArgRef != nil
 		if wasExportInsideNamespace {
+			nameToExport = p.symbols[s.Class.Name.Ref.InnerIndex].OriginalName
 			s.IsExport = false
 		}
 
@@ -10641,7 +10643,7 @@ func (p *parser) visitAndAppendStmt(stmts []js_ast.Stmt, stmt js_ast.Stmt) []js_
 			stmts = append(stmts, js_ast.AssignStmt(
 				js_ast.Expr{Loc: stmt.Loc, Data: p.dotOrMangledPropVisit(
 					js_ast.Expr{Loc: stmt.Loc, Data: &js_ast.EIdentifier{Ref: *p.enclosingNamespaceArgRef}},
-					p.symbols[s.Class.Name.Ref.InnerIndex].OriginalName,
+					nameToExport,
 					s.Class.Name.Loc,
 				)},
 				js_ast.Expr{Loc: s.Class.Name.Loc, Data: &js_ast.EIdentifier{Ref: s.Class.Name.Ref}},

scripts/end-to-end-tests.js

@@ -3628,6 +3628,20 @@ for (let flags of [[], ['--minify', '--keep-names']]) {
     test(['in.js', '--outfile=node.js', '--bundle'].concat(flags), {
       'in.js': `(() => { let Foo = class { static foo() {} }; if (Foo.foo.name !== 'foo') throw 'fail: ' + Foo.foo.name })()`,
     }),
+
+    // See: https://github.com/evanw/esbuild/issues/3199
+    test(['in.ts', '--outfile=node.js', '--target=es6'].concat(flags), {
+      'in.ts': `
+        namespace foo { export class Foo {} }
+        if (foo.Foo.name !== 'Foo') throw 'fail: ' + foo.Foo.name
+      `,
+    }),
+    test(['in.ts', '--outfile=node.js', '--target=esnext'].concat(flags), {
+      'in.ts': `
+        namespace foo { export class Foo {} }
+        if (foo.Foo.name !== 'Foo') throw 'fail: ' + foo.Foo.name
+      `,
+    }),
   )
 }
 tests.push(