Wrap classes with decorators or static properties in an IIFE, even for ES2015+ (#32011)

* Always wrap classes with decorators or static properties in an IIFE

Currently only script targets less than or equal to ES5 will wrap classes.  However, the wrapping is also crucial to file size optimizations for ES2015+ as well.  Without the IIFE wrapper, minification tools do not elide the class.  This is due to references to the class being present within the downlevelled decorator and static property code.
This change represents the full completion of issue #15857

* Accept new baselines

Author: clydin

src/compiler/transformers/ts.ts

@@ -23,11 +23,10 @@ namespace ts {
         IsNamedExternalExport = 1 << 4,
         IsDefaultExternalExport = 1 << 5,
         IsDerivedClass = 1 << 6,
-        UseImmediatelyInvokedFunctionExpression = 1 << 7,
 
         HasAnyDecorators = HasConstructorDecorators | HasMemberDecorators,
         NeedsName = HasStaticInitializedProperties | HasMemberDecorators,
-        MayNeedImmediatelyInvokedFunctionExpression = HasAnyDecorators | HasStaticInitializedProperties,
+        UseImmediatelyInvokedFunctionExpression = HasAnyDecorators | HasStaticInitializedProperties,
         IsExported = IsExportOfNamespace | IsDefaultExternalExport | IsNamedExternalExport,
     }
 
@@ -590,7 +589,6 @@ namespace ts {
             if (isExportOfNamespace(node)) facts |= ClassFacts.IsExportOfNamespace;
             else if (isDefaultExternalModuleExport(node)) facts |= ClassFacts.IsDefaultExternalExport;
             else if (isNamedExternalModuleExport(node)) facts |= ClassFacts.IsNamedExternalExport;
-            if (languageVersion <= ScriptTarget.ES5 && (facts & ClassFacts.MayNeedImmediatelyInvokedFunctionExpression)) facts |= ClassFacts.UseImmediatelyInvokedFunctionExpression;
             return facts;
         }
 
@@ -661,6 +659,12 @@ namespace ts {
                 const iife = createImmediatelyInvokedArrowFunction(statements);
                 setEmitFlags(iife, EmitFlags.TypeScriptClassWrapper);
 
+                // Class comment is already added by the ES2015 transform when targeting ES5 or below.
+                // Only add if targetting ES2015+ to prevent duplicates
+                if (languageVersion > ScriptTarget.ES5) {
+                    addSyntheticLeadingComment(iife, SyntaxKind.MultiLineCommentTrivia, "* @class ");
+                }
+
                 const varStatement = createVariableStatement(
                     /*modifiers*/ undefined,
                     createVariableDeclarationList([
@@ -669,7 +673,7 @@ namespace ts {
                             /*type*/ undefined,
                             iife
                         )
-                    ])
+                    ], languageVersion > ScriptTarget.ES5 ? NodeFlags.Let : undefined)
                 );
 
                 setOriginalNode(varStatement, node);

tests/baselines/reference/awaitAndYieldInProperty.js

@@ -19,27 +19,31 @@ async function* test(x: Promise<string>) {
 
 //// [awaitAndYieldInProperty.js]
 async function* test(x) {
-    var _a, _b, _c, _d, _e, _f, _g, _h, _j;
-    class C {
-        constructor() {
-            this[_a] = await x;
-            this[_c] = yield 2;
-        }
-    }
-    _a = await x, _b = await x, _c = yield 1, _d = yield 3;
-    C[_b] = await x;
-    C[_d] = yield 4;
-    return _j = class {
+    var _a, _b, _c, _d, _e;
+    let C = /** @class */ (() => {
+        var _e, _f, _g, _h;
+        class C {
             constructor() {
                 this[_e] = await x;
                 this[_g] = yield 2;
             }
+        }
+        _e = await x, _f = await x, _g = yield 1, _h = yield 3;
+        C[_f] = await x;
+        C[_h] = yield 4;
+        return C;
+    })();
+    return _e = class {
+            constructor() {
+                this[_a] = await x;
+                this[_c] = yield 2;
+            }
         },
-        _e = await x,
-        _f = await x,
-        _g = yield 1,
-        _h = yield 3,
-        _j[_f] = await x,
-        _j[_h] = yield 4,
-        _j;
+        _a = await x,
+        _b = await x,
+        _c = yield 1,
+        _d = yield 3,
+        _e[_b] = await x,
+        _e[_d] = yield 4,
+        _e;
 }

tests/baselines/reference/classDeclarationCheckUsedBeforeDefinitionInItself.js

@@ -4,6 +4,9 @@ class C3 {
 }
 
 //// [classDeclarationCheckUsedBeforeDefinitionInItself.js]
-class C3 {
-}
-C3.intance = new C3(); // ok
+let C3 = /** @class */ (() => {
+    class C3 {
+    }
+    C3.intance = new C3(); // ok
+    return C3;
+})();

tests/baselines/reference/computedPropertyNames12_ES6.js

@@ -17,16 +17,19 @@ class C {
 }
 
 //// [computedPropertyNames12_ES6.js]
-var _a, _b, _c;
 var s;
 var n;
 var a;
-class C {
-    constructor() {
-        this[_a] = n;
-        this[_b] = 2;
-        this[`hello bye`] = 0;
+let C = /** @class */ (() => {
+    var _a, _b, _c;
+    class C {
+        constructor() {
+            this[_a] = n;
+            this[_b] = 2;
+            this[`hello bye`] = 0;
+        }
     }
-}
-_a = n, s + s, _b = s + n, +s, _c = `hello ${a} bye`;
-C[_c] = 0;
+    _a = n, s + s, _b = s + n, +s, _c = `hello ${a} bye`;
+    C[_c] = 0;
+    return C;
+})();

tests/baselines/reference/computedPropertyNamesWithStaticProperty.js

@@ -11,13 +11,16 @@ class C {
 }
 
 //// [computedPropertyNamesWithStaticProperty.js]
-class C {
-    get [C.staticProp]() {
-        return "hello";
+let C = /** @class */ (() => {
+    class C {
+        get [C.staticProp]() {
+            return "hello";
+        }
+        set [C.staticProp](x) {
+            var y = x;
+        }
+        [C.staticProp]() { }
     }
-    set [C.staticProp](x) {
-        var y = x;
-    }
-    [C.staticProp]() { }
-}
-C.staticProp = 10;
+    C.staticProp = 10;
+    return C;
+})();

tests/baselines/reference/decoratedClassExportsCommonJS1.js

@@ -14,12 +14,15 @@ var __decorate = (this && this.__decorate) || function (decorators, target, key,
     else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
     return c > 3 && r && Object.defineProperty(target, key, r), r;
 };
-var Testing123_1;
 Object.defineProperty(exports, "__esModule", { value: true });
-let Testing123 = Testing123_1 = class Testing123 {
-};
-Testing123.prop1 = Testing123_1.prop0;
-Testing123 = Testing123_1 = __decorate([
-    Something({ v: () => Testing123_1 })
-], Testing123);
+let Testing123 = /** @class */ (() => {
+    var Testing123_1;
+    let Testing123 = Testing123_1 = class Testing123 {
+    };
+    Testing123.prop1 = Testing123_1.prop0;
+    Testing123 = Testing123_1 = __decorate([
+        Something({ v: () => Testing123_1 })
+    ], Testing123);
+    return Testing123;
+})();
 exports.Testing123 = Testing123;

tests/baselines/reference/decoratedClassExportsCommonJS2.js

@@ -12,11 +12,14 @@ var __decorate = (this && this.__decorate) || function (decorators, target, key,
     else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
     return c > 3 && r && Object.defineProperty(target, key, r), r;
 };
-var Testing123_1;
 Object.defineProperty(exports, "__esModule", { value: true });
-let Testing123 = Testing123_1 = class Testing123 {
-};
-Testing123 = Testing123_1 = __decorate([
-    Something({ v: () => Testing123_1 })
-], Testing123);
+let Testing123 = /** @class */ (() => {
+    var Testing123_1;
+    let Testing123 = Testing123_1 = class Testing123 {
+    };
+    Testing123 = Testing123_1 = __decorate([
+        Something({ v: () => Testing123_1 })
+    ], Testing123);
+    return Testing123;
+})();
 exports.Testing123 = Testing123;

tests/baselines/reference/decoratedClassExportsSystem1.js

@@ -16,17 +16,21 @@ System.register([], function (exports_1, context_1) {
         else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
         return c > 3 && r && Object.defineProperty(target, key, r), r;
     };
-    var Testing123_1, Testing123;
+    var Testing123;
     var __moduleName = context_1 && context_1.id;
     return {
         setters: [],
         execute: function () {
-            Testing123 = Testing123_1 = class Testing123 {
-            };
-            Testing123.prop1 = Testing123_1.prop0;
-            Testing123 = Testing123_1 = __decorate([
-                Something({ v: () => Testing123_1 })
-            ], Testing123);
+            Testing123 = /** @class */ (() => {
+                var Testing123_1;
+                let Testing123 = Testing123_1 = class Testing123 {
+                };
+                Testing123.prop1 = Testing123_1.prop0;
+                Testing123 = Testing123_1 = __decorate([
+                    Something({ v: () => Testing123_1 })
+                ], Testing123);
+                return Testing123;
+            })();
             exports_1("Testing123", Testing123);
         }
     };

tests/baselines/reference/decoratedClassExportsSystem2.js

@@ -13,16 +13,20 @@ System.register([], function (exports_1, context_1) {
         else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
         return c > 3 && r && Object.defineProperty(target, key, r), r;
     };
-    var Testing123_1, Testing123;
+    var Testing123;
     var __moduleName = context_1 && context_1.id;
     return {
         setters: [],
         execute: function () {
-            Testing123 = Testing123_1 = class Testing123 {
-            };
-            Testing123 = Testing123_1 = __decorate([
-                Something({ v: () => Testing123_1 })
-            ], Testing123);
+            Testing123 = /** @class */ (() => {
+                var Testing123_1;
+                let Testing123 = Testing123_1 = class Testing123 {
+                };
+                Testing123 = Testing123_1 = __decorate([
+                    Something({ v: () => Testing123_1 })
+                ], Testing123);
+                return Testing123;
+            })();
             exports_1("Testing123", Testing123);
         }
     };

tests/baselines/reference/decoratedClassFromExternalModule.js

@@ -17,10 +17,13 @@ var __decorate = (this && this.__decorate) || function (decorators, target, key,
     return c > 3 && r && Object.defineProperty(target, key, r), r;
 };
 function decorate(target) { }
-let Decorated = class Decorated {
-};
-Decorated = __decorate([
-    decorate
-], Decorated);
+let Decorated = /** @class */ (() => {
+    let Decorated = class Decorated {
+    };
+    Decorated = __decorate([
+        decorate
+    ], Decorated);
+    return Decorated;
+})();
 export default Decorated;
 //// [undecorated.js]