fix #2793: bundling edge case with dynamic import

CHANGELOG.md

@@ -10,6 +10,22 @@
 
     This information is helpful when trying to reduce the size of your bundle. Using the ESM variant of a dependency instead of the CommonJS variant always results in a faster and smaller bundle because it omits CommonJS wrappers, and also may result in better tree-shaking as it allows esbuild to perform tree-shaking at the statement level instead of the module level.
 
+* Fix a bundling edge case with dynamic import ([#2793](https://github.com/evanw/esbuild/issues/2793))
+
+    This release fixes a bug where esbuild's bundler could produce incorrect output. The problematic edge case involves the entry point importing itself using a dynamic `import()` expression in an imported file, like this:
+
+    ```js
+    // src/a.js
+    export const A = 42;
+
+    // src/b.js
+    export const B = async () => (await import(".")).A
+
+    // src/index.js
+    export * from "./a"
+    export * from "./b"
+    ```
+
 ## 0.16.14
 
 * Preserve some comments in expressions ([#2721](https://github.com/evanw/esbuild/issues/2721))

internal/bundler_tests/bundler_splitting_test.go

@@ -550,3 +550,50 @@ func TestSplittingChunkPathDirPlaceholderImplicitOutbase(t *testing.T) {
 		},
 	})
 }
+
+func TestEdgeCaseIssue2793WithSplitting(t *testing.T) {
+	splitting_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/src/a.js": `
+				export const A = 42;
+			`,
+			"/src/b.js": `
+				export const B = async () => (await import(".")).A
+			`,
+			"/src/index.js": `
+				export * from "./a"
+				export * from "./b"
+			`,
+		},
+		entryPaths: []string{"/src/index.js"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			OutputFormat:  config.FormatESModule,
+			CodeSplitting: true,
+			AbsOutputDir:  "/out",
+		},
+	})
+}
+
+func TestEdgeCaseIssue2793WithoutSplitting(t *testing.T) {
+	splitting_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/src/a.js": `
+				export const A = 42;
+			`,
+			"/src/b.js": `
+				export const B = async () => (await import(".")).A
+			`,
+			"/src/index.js": `
+				export * from "./a"
+				export * from "./b"
+			`,
+		},
+		entryPaths: []string{"/src/index.js"},
+		options: config.Options{
+			Mode:         config.ModeBundle,
+			OutputFormat: config.FormatESModule,
+			AbsOutputDir: "/out",
+		},
+	})
+}

internal/bundler_tests/snapshots/snapshots_splitting.txt

@@ -1,3 +1,53 @@
+TestEdgeCaseIssue2793WithSplitting
+---------- /out/index.js ----------
+// src/a.js
+var A = 42;
+
+// src/b.js
+var B = async () => (await import("./index.js")).A;
+export {
+  A,
+  B
+};
+
+================================================================================
+TestEdgeCaseIssue2793WithoutSplitting
+---------- /out/index.js ----------
+// src/a.js
+var A;
+var init_a = __esm({
+  "src/a.js"() {
+    A = 42;
+  }
+});
+
+// src/b.js
+var B;
+var init_b = __esm({
+  "src/b.js"() {
+    B = async () => (await Promise.resolve().then(() => (init_src(), src_exports))).A;
+  }
+});
+
+// src/index.js
+var src_exports = {};
+__export(src_exports, {
+  A: () => A,
+  B: () => B
+});
+var init_src = __esm({
+  "src/index.js"() {
+    init_a();
+    init_b();
+  }
+});
+init_src();
+export {
+  A,
+  B
+};
+
+================================================================================
 TestSplittingAssignToLocal
 ---------- /out/a.js ----------
 import {

internal/linker/linker.go

@@ -780,13 +780,7 @@ func (c *linkerContext) computeCrossChunkDependencies() {
 	c.timer.Begin("Compute cross-chunk dependencies")
 	defer c.timer.End("Compute cross-chunk dependencies")
 
-	jsChunks := 0
-	for _, chunk := range c.chunks {
-		if _, ok := chunk.chunkRepr.(*chunkReprJS); ok {
-			jsChunks++
-		}
-	}
-	if jsChunks < 2 {
+	if !c.options.CodeSplitting {
 		// No need to compute cross-chunk dependencies if there can't be any
 		return
 	}
@@ -2866,7 +2860,10 @@ func (c *linkerContext) markFileLiveForTreeShaking(sourceIndex uint32) {
 }
 
 func (c *linkerContext) isExternalDynamicImport(record *ast.ImportRecord, sourceIndex uint32) bool {
-	return record.Kind == ast.ImportDynamic && c.graph.Files[record.SourceIndex.GetIndex()].IsEntryPoint() && record.SourceIndex.GetIndex() != sourceIndex
+	return c.options.CodeSplitting &&
+		record.Kind == ast.ImportDynamic &&
+		c.graph.Files[record.SourceIndex.GetIndex()].IsEntryPoint() &&
+		record.SourceIndex.GetIndex() != sourceIndex
 }
 
 func (c *linkerContext) markPartLiveForTreeShaking(sourceIndex uint32, partIndex uint32) {

scripts/end-to-end-tests.js

@@ -1342,6 +1342,36 @@ for (const minify of [[], ['--minify']]) {
       'node2.ts': `throw [foo.bar, require('./node2.ts')] // Force this file to be lazily initialized so foo.js is lazily initialized`,
       'foo.js': `export let foo = {bar: 123}`,
     }),
+
+    // https://github.com/evanw/esbuild/issues/2793
+    test(['--bundle', 'src/index.js', '--outfile=node.js', '--format=esm'].concat(minify), {
+      'src/a.js': `
+        export const A = 42;
+      `,
+      'src/b.js': `
+        export const B = async () => (await import(".")).A
+      `,
+      'src/index.js': `
+        export * from "./a"
+        export * from "./b"
+        import { B } from '.'
+        export let async = async () => { if (42 !== await B()) throw 'fail' }
+      `,
+    }, { async: true }),
+    test(['--bundle', 'src/node.js', '--outdir=.', '--format=esm', '--splitting'].concat(minify), {
+      'src/a.js': `
+        export const A = 42;
+      `,
+      'src/b.js': `
+        export const B = async () => (await import("./node")).A
+      `,
+      'src/node.js': `
+        export * from "./a"
+        export * from "./b"
+        import { B } from './node'
+        export let async = async () => { if (42 !== await B()) throw 'fail' }
+      `,
+    }, { async: true }),
   )
 }