fix #2914: do not emit computed declare fields

CHANGELOG.md

@@ -2,6 +2,39 @@
 
 ## Unreleased
 
+* Fix TypeScript code translation for certain computed `declare` class fields ([#2914](https://github.com/evanw/esbuild/issues/2914))
+
+    In TypeScript, the key of a computed `declare` class field should only be preserved if there are no decorators for that field. Previously esbuild always preserved the key, but esbuild will now remove the key to match the output of the TypeScript compiler:
+
+    ```ts
+    // Original code
+    declare function dec(a: any, b: any): any
+    declare const removeMe: unique symbol
+    declare const keepMe: unique symbol
+    class X {
+        declare [removeMe]: any
+        @dec declare [keepMe]: any
+    }
+
+    // Old output
+    var _a;
+    class X {
+    }
+    removeMe, _a = keepMe;
+    __decorateClass([
+      dec
+    ], X.prototype, _a, 2);
+
+    // New output
+    var _a;
+    class X {
+    }
+    _a = keepMe;
+    __decorateClass([
+      dec
+    ], X.prototype, _a, 2);
+    ```
+
 * Fix a crash with path resolution error generation ([#2913](https://github.com/evanw/esbuild/issues/2913))
 
     In certain situations, a module containing an invalid import path could previously cause esbuild to crash when it attempts to generate a more helpful error message. This crash has been fixed.

internal/bundler_tests/snapshots/snapshots_ts.txt

@@ -232,7 +232,7 @@ TestTSDeclareClassFields
 // define-false/index.ts
 var Foo = class {
 };
-() => null, c, () => null, d, () => null, C, () => null, D;
+() => null, c, () => null, C;
 (() => new Foo())();
 
 // define-true/index.ts
@@ -243,7 +243,7 @@ var Bar = class {
     __publicField(this, _a);
   }
 };
-_a = (() => null, c), () => null, d, _b = (() => null, C), () => null, D;
+_a = (() => null, c), _b = (() => null, C);
 __publicField(Bar, "A");
 __publicField(Bar, _b);
 (() => new Bar())();

internal/js_parser/js_parser.go

@@ -2061,13 +2061,16 @@ func (p *parser) parseProperty(startLoc logger.Loc, kind js_ast.PropertyKind, op
 						scopeIndex := len(p.scopesInOrder)
 
 						if prop, ok := p.parseProperty(startLoc, kind, opts, nil); ok &&
-							prop.Kind == js_ast.PropertyNormal && prop.ValueOrNil.Data == nil {
+							prop.Kind == js_ast.PropertyNormal && prop.ValueOrNil.Data == nil && len(opts.tsDecorators) > 0 {
 							// If this is a well-formed class field with the "declare" keyword,
-							// keep the declaration to preserve its side-effects, which may
-							// include the computed key and/or the TypeScript decorators:
+							// only keep the declaration to preserve its side-effects when
+							// there are TypeScript decorators present:
 							//
 							//   class Foo {
+							//     // Remove this
 							//     declare [(console.log('side effect 1'), 'foo')]
+							//
+							//     // Keep this
 							//     @decorator(console.log('side effect 2')) declare bar
 							//   }
 							//

internal/js_parser/ts_parser_test.go

@@ -2512,7 +2512,7 @@ func TestTSNoAmbiguousLessThan(t *testing.T) {
 			"<stdin>: ERROR: Unexpected \"=\"\n")
 }
 
-func TestClassSideEffectOrder(t *testing.T) {
+func TestTSClassSideEffectOrder(t *testing.T) {
 	// The order of computed property side effects must not change
 	expectPrintedTS(t, `class Foo {
 	[a()]() {}
@@ -2541,7 +2541,7 @@ Foo[_b] = 1;
 `)
 }
 
-func TestMangleTSStringEnumLength(t *testing.T) {
+func TestTSMangleStringEnumLength(t *testing.T) {
 	expectPrintedTS(t, "enum x { y = '' } z = x.y.length",
 		"var x = /* @__PURE__ */ ((x) => {\n  x[\"y\"] = \"\";\n  return x;\n})(x || {});\nz = \"\" /* y */.length;\n")