fix #251: code splitting bug with re-export cycle

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+* Fix code splitting bug with re-export cycles ([#251](https://github.com/evanw/esbuild/issues/251))
+
+    Two files that both re-export each other could cause invalid code to be generated when code splitting is enabled. The specific failure was an `export` statement without a matching `import` statement from the shared code chunk. This bug has been fixed.
+
 ## 0.6.1
 
 * Allow bundling with stdin as input ([#212](https://github.com/evanw/esbuild/issues/212))

internal/bundler/bundler_splitting_test.go

@@ -413,3 +413,60 @@ export {
 		},
 	})
 }
+
+func TestSplittingCircularReferenceIssue251(t *testing.T) {
+	expectBundled(t, bundled{
+		files: map[string]string{
+			"/a.js": `
+				export * from './b.js';
+				export var p = 5;
+			`,
+			"/b.js": `
+				export * from './a.js';
+				export var q = 6;
+			`,
+		},
+		entryPaths: []string{"/a.js", "/b.js"},
+		options: config.Options{
+			IsBundling:    true,
+			CodeSplitting: true,
+			OutputFormat:  config.FormatESModule,
+			AbsOutputDir:  "/out",
+		},
+		expected: map[string]string{
+			"/out/a.js": `import {
+  p,
+  q
+} from "./chunk.xL6KqlYO.js";
+
+// /a.js
+export {
+  p,
+  q
+};
+`,
+			"/out/b.js": `import {
+  p,
+  q
+} from "./chunk.xL6KqlYO.js";
+
+// /b.js
+export {
+  p,
+  q
+};
+`,
+			"/out/chunk.xL6KqlYO.js": `// /b.js
+var q = 6;
+
+// /a.js
+var p = 5;
+
+export {
+  p,
+  q
+};
+`,
+		},
+	})
+}

internal/bundler/linker.go

@@ -1573,6 +1573,7 @@ func (c *linkerContext) addExportsForExportStar(
 	}
 	visited[sourceIndex] = true
 	file := &c.files[sourceIndex]
+	fileMeta := &c.fileMeta[sourceIndex]
 
 	for _, importRecordIndex := range file.ast.ExportStarImportRecords {
 		record := &file.ast.ImportRecords[importRecordIndex]
@@ -1623,6 +1624,13 @@ func (c *linkerContext) addExportsForExportStar(
 					pathLoc:          &pathLoc,
 					isFromExportStar: true,
 				}
+
+				// Make sure the symbol is marked as imported so that code splitting
+				// imports it correctly if it ends up being shared with another chunk
+				fileMeta.importsToBind[ref] = importToBind{
+					ref:         ref,
+					sourceIndex: otherSourceIndex,
+				}
 			} else if existing.sourceIndex != otherSourceIndex {
 				// Two different re-exports colliding makes it ambiguous
 				existing.isAmbiguous = true