fix #1425: super inside arrow inside lowered async

evanw · Oct 15, 2021 · b332f93 · b332f93
1 parent 68e369d
commit b332f93
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,39 @@
 # Changelog
 
+## Unreleased
+
+* Fix `super` inside arrow function inside lowered `async` function ([#1425](https://github.com/evanw/esbuild/issues/1425))
+
+    When an `async` function is transformed into a regular function for target environments that don't support `async` such as `--target=es6`, references to `super` inside that function must be transformed too since the `async`-to-regular function transformation moves the function body into a nested function, so the `super` references are no longer syntactically valid. However, this transform didn't handle an edge case and `super` references inside of an arrow function were overlooked. This release fixes this bug:
+
+    ```js
+    // Original code
+    class Foo extends Bar {
+      async foo() {
+        return () => super.foo()
+      }
+    }
+
+    // Old output (with --target=es6)
+    class Foo extends Bar {
+      foo() {
+        return __async(this, null, function* () {
+          return () => super.foo();
+        });
+      }
+    }
+
+    // New output (with --target=es6)
+    class Foo extends Bar {
+      foo() {
+        var __super = (key) => super[key];
+        return __async(this, null, function* () {
+          return () => __super("foo").call(this);
+        });
+      }
+    }
+    ```
+
 ## 0.13.7
 
 * Minify CSS alpha values correctly ([#1682](https://github.com/evanw/esbuild/issues/1682))

diff --git a/internal/bundler/bundler_lower_test.go b/internal/bundler/bundler_lower_test.go
@@ -920,6 +920,43 @@ obj-method.js: error: Transforming object literal extensions to the configured t
 	})
 }
 
+func TestLowerAsyncSuperES2017NoBundle(t *testing.T) {
+	lower_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.js": `
+				class Derived extends Base {
+					async test(key) {
+						return [
+							await super.foo,
+							await super[key],
+
+							await super.foo.name,
+							await super[key].name,
+							await super.foo?.name,
+							await super[key]?.name,
+
+							await super.foo(1, 2),
+							await super[key](1, 2),
+							await super.foo?.(1, 2),
+							await super[key]?.(1, 2),
+
+							await (() => super.foo)(),
+							await (() => super[key])(),
+							await (() => super.foo())(),
+							await (() => super[key]())(),
+						]
+					}
+				}
+			`,
+		},
+		entryPaths: []string{"/entry.js"},
+		options: config.Options{
+			UnsupportedJSFeatures: es(2017),
+			AbsOutputFile:         "/out.js",
+		},
+	})
+}
+
 func TestLowerAsyncSuperES2016NoBundle(t *testing.T) {
 	lower_suite.expectBundled(t, bundled{
 		files: map[string]string{
@@ -939,6 +976,11 @@ func TestLowerAsyncSuperES2016NoBundle(t *testing.T) {
 							await super[key](1, 2),
 							await super.foo?.(1, 2),
 							await super[key]?.(1, 2),
+
+							await (() => super.foo)(),
+							await (() => super[key])(),
+							await (() => super.foo())(),
+							await (() => super[key]())(),
 						]
 					}
 				}

diff --git a/internal/bundler/snapshots/snapshots_lower.txt b/internal/bundler/snapshots/snapshots_lower.txt
@@ -109,12 +109,41 @@ class Derived extends Base {
         yield __super("foo").call(this, 1, 2),
         yield __super(key).call(this, 1, 2),
         yield (_c = __super("foo")) == null ? void 0 : _c.call(this, 1, 2),
-        yield (_d = __super(key)) == null ? void 0 : _d.call(this, 1, 2)
+        yield (_d = __super(key)) == null ? void 0 : _d.call(this, 1, 2),
+        yield (() => __super("foo"))(),
+        yield (() => __super(key))(),
+        yield (() => __super("foo").call(this))(),
+        yield (() => __super(key).call(this))()
       ];
     });
   }
 }
 
+================================================================================
+TestLowerAsyncSuperES2017NoBundle
+---------- /out.js ----------
+class Derived extends Base {
+  async test(key) {
+    var _a, _b, _c, _d;
+    return [
+      await super.foo,
+      await super[key],
+      await super.foo.name,
+      await super[key].name,
+      await ((_a = super.foo) == null ? void 0 : _a.name),
+      await ((_b = super[key]) == null ? void 0 : _b.name),
+      await super.foo(1, 2),
+      await super[key](1, 2),
+      await ((_c = super.foo) == null ? void 0 : _c.call(this, 1, 2)),
+      await ((_d = super[key]) == null ? void 0 : _d.call(this, 1, 2)),
+      await (() => super.foo)(),
+      await (() => super[key])(),
+      await (() => super.foo())(),
+      await (() => super[key]())()
+    ];
+  }
+}
+
 ================================================================================
 TestLowerAsyncThis2016CommonJS
 ---------- /out.js ----------

diff --git a/internal/js_parser/js_parser.go b/internal/js_parser/js_parser.go
@@ -494,8 +494,6 @@ type fnOrArrowDataParse struct {
 // restored on the call stack around code that parses nested functions and
 // arrow expressions.
 type fnOrArrowDataVisit struct {
-	superIndexRef *js_ast.Ref
-
 	isArrow            bool
 	isAsync            bool
 	isGenerator        bool
@@ -513,6 +511,9 @@ type fnOrArrowDataVisit struct {
 // restored on the call stack around code that parses nested functions (but not
 // nested arrow functions).
 type fnOnlyDataVisit struct {
+	superIndexRef    *js_ast.Ref
+	shouldLowerSuper bool
+
 	// This is a reference to the magic "arguments" variable that exists inside
 	// functions in JavaScript. It will be non-nil inside functions and nil
 	// otherwise.
@@ -12813,6 +12814,7 @@ func (p *parser) visitFn(fn *js_ast.Fn, scopeLoc logger.Loc) {
 		isThisNested:       true,
 		isNewTargetAllowed: true,
 		argumentsRef:       &fn.ArgumentsRef,
+		shouldLowerSuper:   fn.IsAsync && p.options.unsupportedJSFeatures.Has(compat.AsyncAwait),
 	}
 
 	if fn.Name != nil {

diff --git a/internal/js_parser/js_parser_lower.go b/internal/js_parser/js_parser_lower.go
@@ -443,12 +443,12 @@ func (p *parser) lowerFunction(
 		returnStmt := js_ast.Stmt{Loc: bodyLoc, Data: &js_ast.SReturn{ValueOrNil: callAsync}}
 
 		// Prepend the "super" index function if necessary
-		if p.fnOrArrowDataVisit.superIndexRef != nil {
+		if p.fnOnlyDataVisit.superIndexRef != nil {
 			argRef := p.newSymbol(js_ast.SymbolOther, "key")
-			p.currentScope.Generated = append(p.currentScope.Generated, *p.fnOrArrowDataVisit.superIndexRef, argRef)
+			p.currentScope.Generated = append(p.currentScope.Generated, *p.fnOnlyDataVisit.superIndexRef, argRef)
 			superIndexStmt := js_ast.Stmt{Loc: bodyLoc, Data: &js_ast.SLocal{
 				Decls: []js_ast.Decl{{
-					Binding: js_ast.Binding{Loc: bodyLoc, Data: &js_ast.BIdentifier{Ref: *p.fnOrArrowDataVisit.superIndexRef}},
+					Binding: js_ast.Binding{Loc: bodyLoc, Data: &js_ast.BIdentifier{Ref: *p.fnOnlyDataVisit.superIndexRef}},
 					ValueOrNil: js_ast.Expr{Loc: bodyLoc, Data: &js_ast.EArrow{
 						Args: []js_ast.Arg{{
 							Binding: js_ast.Binding{Loc: bodyLoc, Data: &js_ast.BIdentifier{Ref: argRef}},
@@ -2729,21 +2729,21 @@ func (p *parser) lowerTemplateLiteral(loc logger.Loc, e *js_ast.ETemplate) js_as
 }
 
 func (p *parser) shouldLowerSuperPropertyAccess(expr js_ast.Expr) bool {
-	if p.fnOrArrowDataVisit.isAsync && p.options.unsupportedJSFeatures.Has(compat.AsyncAwait) {
+	if p.fnOnlyDataVisit.shouldLowerSuper {
 		_, isSuper := expr.Data.(*js_ast.ESuper)
 		return isSuper
 	}
 	return false
 }
 
 func (p *parser) lowerSuperPropertyAccess(loc logger.Loc, key js_ast.Expr) js_ast.Expr {
-	if p.fnOrArrowDataVisit.superIndexRef == nil {
+	if p.fnOnlyDataVisit.superIndexRef == nil {
 		ref := p.newSymbol(js_ast.SymbolOther, "__super")
-		p.fnOrArrowDataVisit.superIndexRef = &ref
+		p.fnOnlyDataVisit.superIndexRef = &ref
 	}
-	p.recordUsage(*p.fnOrArrowDataVisit.superIndexRef)
+	p.recordUsage(*p.fnOnlyDataVisit.superIndexRef)
 	return js_ast.Expr{Loc: loc, Data: &js_ast.ECall{
-		Target: js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: *p.fnOrArrowDataVisit.superIndexRef}},
+		Target: js_ast.Expr{Loc: loc, Data: &js_ast.EIdentifier{Ref: *p.fnOnlyDataVisit.superIndexRef}},
 		Args:   []js_ast.Expr{key},
 	}}
 }