Introduces new flag for optimization hints

src/compiler/commandLineParser.ts

@@ -986,6 +986,13 @@ namespace ts {
             category: Diagnostics.Advanced_Options,
             description: Diagnostics.Resolve_keyof_to_string_valued_property_names_only_no_numbers_or_symbols,
         },
+        {
+          name: "addOptimizationHints",
+          type: "boolean",
+          affectsEmit: true,
+          category: Diagnostics.Advanced_Options,
+          description: Diagnostics.Resolve_keyof_to_string_valued_property_names_only_no_numbers_or_symbols,
+        },
         {
             // A list of plugins to load in the language service
             name: "plugins",

src/compiler/diagnosticMessages.json

@@ -4400,6 +4400,10 @@
         "category": "Error",
         "code": 6233
     },
+    "Emit code hints for optimizers and minifiers.": {
+      "category": "Message",
+      "code": 6234
+    },
 
     "Projects to reference": {
         "category": "Message",

src/compiler/transformers/ts.ts

@@ -23,10 +23,10 @@ namespace ts {
         IsNamedExternalExport = 1 << 4,
         IsDefaultExternalExport = 1 << 5,
         IsDerivedClass = 1 << 6,
+        UseImmediatelyInvokedFunctionExpression = 1 << 7,
 
         HasAnyDecorators = HasConstructorDecorators | HasMemberDecorators,
         NeedsName = HasStaticInitializedProperties | HasMemberDecorators,
-        UseImmediatelyInvokedFunctionExpression = HasAnyDecorators | HasStaticInitializedProperties,
         IsExported = IsExportOfNamespace | IsDefaultExternalExport | IsNamedExternalExport,
     }
 
@@ -585,6 +585,17 @@ namespace ts {
             return parameter.decorators !== undefined && parameter.decorators.length > 0;
         }
 
+        function shouldWrapClassWithIIFE(facts: ClassFacts) {
+          if (compilerOptions.addOptimizationHints === false) return false;
+          if (facts & ClassFacts.HasAnyDecorators) return true;
+          if (facts & ClassFacts.HasStaticInitializedProperties) {
+              if (languageVersion < ScriptTarget.ESNext) return true;
+              else if (languageVersion === ScriptTarget.ESNext && !compilerOptions.useDefineForClassFields) return true;
+          }
+
+          return false;
+        }
+
         function getClassFacts(node: ClassDeclaration, staticProperties: readonly PropertyDeclaration[]) {
             let facts = ClassFacts.None;
             if (some(staticProperties)) facts |= ClassFacts.HasStaticInitializedProperties;
@@ -595,6 +606,7 @@ namespace ts {
             if (isExportOfNamespace(node)) facts |= ClassFacts.IsExportOfNamespace;
             else if (isDefaultExternalModuleExport(node)) facts |= ClassFacts.IsDefaultExternalExport;
             else if (isNamedExternalModuleExport(node)) facts |= ClassFacts.IsNamedExternalExport;
+            if (shouldWrapClassWithIIFE(facts)) facts |= ClassFacts.UseImmediatelyInvokedFunctionExpression;
             return facts;
         }
 

src/compiler/types.ts

@@ -5133,6 +5133,7 @@ namespace ts {
     export type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[] | ProjectReference[] | null | undefined;
 
     export interface CompilerOptions {
+        addOptimizationHints?: boolean;
         /*@internal*/ all?: boolean;
         allowJs?: boolean;
         /*@internal*/ allowNonTsExtensions?: boolean;

tests/baselines/reference/addOptimizationHints.errors.txt

@@ -0,0 +1,23 @@
+tests/cases/compiler/addOptimizationHints.ts(13,2): error TS2304: Cannot find name 'decorate'.
+
+
+==== tests/cases/compiler/addOptimizationHints.ts (1 errors) ====
+    class HasNoStatics {
+      value: unknown;
+      method() {}
+    }
+
+    class HasStatic {
+      static value = 0;
+      static someMethod() {}
+
+      method() {}
+    }
+
+    @decorate
+     ~~~~~~~~
+!!! error TS2304: Cannot find name 'decorate'.
+    class HasDecorator {
+      method() {}
+    }
+

tests/baselines/reference/addOptimizationHints.js

@@ -0,0 +1,40 @@
+//// [addOptimizationHints.ts]
+class HasNoStatics {
+  value: unknown;
+  method() {}
+}
+
+class HasStatic {
+  static value = 0;
+  static someMethod() {}
+
+  method() {}
+}
+
+@decorate
+class HasDecorator {
+  method() {}
+}
+
+
+//// [addOptimizationHints.js]
+class HasNoStatics {
+    method() { }
+}
+let HasStatic = /** @class */ (() => {
+    class HasStatic {
+        static someMethod() { }
+        method() { }
+    }
+    HasStatic.value = 0;
+    return HasStatic;
+})();
+let HasDecorator = /** @class */ (() => {
+    let HasDecorator = class HasDecorator {
+        method() { }
+    };
+    HasDecorator = __decorate([
+        decorate
+    ], HasDecorator);
+    return HasDecorator;
+})();

tests/baselines/reference/addOptimizationHints.symbols

@@ -0,0 +1,32 @@
+=== tests/cases/compiler/addOptimizationHints.ts ===
+class HasNoStatics {
+>HasNoStatics : Symbol(HasNoStatics, Decl(addOptimizationHints.ts, 0, 0))
+
+  value: unknown;
+>value : Symbol(HasNoStatics.value, Decl(addOptimizationHints.ts, 0, 20))
+
+  method() {}
+>method : Symbol(HasNoStatics.method, Decl(addOptimizationHints.ts, 1, 17))
+}
+
+class HasStatic {
+>HasStatic : Symbol(HasStatic, Decl(addOptimizationHints.ts, 3, 1))
+
+  static value = 0;
+>value : Symbol(HasStatic.value, Decl(addOptimizationHints.ts, 5, 17))
+
+  static someMethod() {}
+>someMethod : Symbol(HasStatic.someMethod, Decl(addOptimizationHints.ts, 6, 19))
+
+  method() {}
+>method : Symbol(HasStatic.method, Decl(addOptimizationHints.ts, 7, 24))
+}
+
+@decorate
+class HasDecorator {
+>HasDecorator : Symbol(HasDecorator, Decl(addOptimizationHints.ts, 10, 1))
+
+  method() {}
+>method : Symbol(HasDecorator.method, Decl(addOptimizationHints.ts, 13, 20))
+}
+

tests/baselines/reference/addOptimizationHints.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/addOptimizationHints.ts ===
+class HasNoStatics {
+>HasNoStatics : HasNoStatics
+
+  value: unknown;
+>value : unknown
+
+  method() {}
+>method : () => void
+}
+
+class HasStatic {
+>HasStatic : HasStatic
+
+  static value = 0;
+>value : number
+>0 : 0
+
+  static someMethod() {}
+>someMethod : () => void
+
+  method() {}
+>method : () => void
+}
+
+@decorate
+>decorate : any
+
+class HasDecorator {
+>HasDecorator : HasDecorator
+
+  method() {}
+>method : () => void
+}
+

tests/baselines/reference/addOptimizationHintsFalse.errors.txt

@@ -0,0 +1,23 @@
+tests/cases/compiler/addOptimizationHintsFalse.ts(13,2): error TS2304: Cannot find name 'decorate'.
+
+
+==== tests/cases/compiler/addOptimizationHintsFalse.ts (1 errors) ====
+    class HasNoStatics {
+      value: unknown;
+      method() {}
+    }
+
+    class HasStatic {
+      static value = 0;
+      static someMethod() {}
+
+      method() {}
+    }
+
+    @decorate
+     ~~~~~~~~
+!!! error TS2304: Cannot find name 'decorate'.
+    class HasDecorator {
+      method() {}
+    }
+

tests/baselines/reference/addOptimizationHintsFalse.js

@@ -0,0 +1,34 @@
+//// [addOptimizationHintsFalse.ts]
+class HasNoStatics {
+  value: unknown;
+  method() {}
+}
+
+class HasStatic {
+  static value = 0;
+  static someMethod() {}
+
+  method() {}
+}
+
+@decorate
+class HasDecorator {
+  method() {}
+}
+
+
+//// [addOptimizationHintsFalse.js]
+class HasNoStatics {
+    method() { }
+}
+class HasStatic {
+    static someMethod() { }
+    method() { }
+}
+HasStatic.value = 0;
+let HasDecorator = class HasDecorator {
+    method() { }
+};
+HasDecorator = __decorate([
+    decorate
+], HasDecorator);

tests/baselines/reference/addOptimizationHintsFalse.symbols

@@ -0,0 +1,32 @@
+=== tests/cases/compiler/addOptimizationHintsFalse.ts ===
+class HasNoStatics {
+>HasNoStatics : Symbol(HasNoStatics, Decl(addOptimizationHintsFalse.ts, 0, 0))
+
+  value: unknown;
+>value : Symbol(HasNoStatics.value, Decl(addOptimizationHintsFalse.ts, 0, 20))
+
+  method() {}
+>method : Symbol(HasNoStatics.method, Decl(addOptimizationHintsFalse.ts, 1, 17))
+}
+
+class HasStatic {
+>HasStatic : Symbol(HasStatic, Decl(addOptimizationHintsFalse.ts, 3, 1))
+
+  static value = 0;
+>value : Symbol(HasStatic.value, Decl(addOptimizationHintsFalse.ts, 5, 17))
+
+  static someMethod() {}
+>someMethod : Symbol(HasStatic.someMethod, Decl(addOptimizationHintsFalse.ts, 6, 19))
+
+  method() {}
+>method : Symbol(HasStatic.method, Decl(addOptimizationHintsFalse.ts, 7, 24))
+}
+
+@decorate
+class HasDecorator {
+>HasDecorator : Symbol(HasDecorator, Decl(addOptimizationHintsFalse.ts, 10, 1))
+
+  method() {}
+>method : Symbol(HasDecorator.method, Decl(addOptimizationHintsFalse.ts, 13, 20))
+}
+

tests/baselines/reference/addOptimizationHintsFalse.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/addOptimizationHintsFalse.ts ===
+class HasNoStatics {
+>HasNoStatics : HasNoStatics
+
+  value: unknown;
+>value : unknown
+
+  method() {}
+>method : () => void
+}
+
+class HasStatic {
+>HasStatic : HasStatic
+
+  static value = 0;
+>value : number
+>0 : 0
+
+  static someMethod() {}
+>someMethod : () => void
+
+  method() {}
+>method : () => void
+}
+
+@decorate
+>decorate : any
+
+class HasDecorator {
+>HasDecorator : HasDecorator
+
+  method() {}
+>method : () => void
+}
+

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2651,6 +2651,7 @@ declare namespace ts {
     }
     export type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[] | ProjectReference[] | null | undefined;
     export interface CompilerOptions {
+        addOptimizationHints?: boolean;
         allowJs?: boolean;
         allowSyntheticDefaultImports?: boolean;
         allowUmdGlobalAccess?: boolean;

tests/baselines/reference/api/typescript.d.ts

@@ -2651,6 +2651,7 @@ declare namespace ts {
     }
     export type CompilerOptionsValue = string | number | boolean | (string | number)[] | string[] | MapLike<string[]> | PluginImport[] | ProjectReference[] | null | undefined;
     export interface CompilerOptions {
+        addOptimizationHints?: boolean;
         allowJs?: boolean;
         allowSyntheticDefaultImports?: boolean;
         allowUmdGlobalAccess?: boolean;

tests/baselines/reference/showConfig/Shows tsconfig for single option/addOptimizationHints/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "addOptimizationHints": true
+    }
+}

tests/baselines/reference/thisInClassBodyStaticESNext.js

@@ -11,13 +11,10 @@ class Foo {
 
 //// [thisInClassBodyStaticESNext.js]
 // all are allowed with es-compliant class field emit
-let Foo = /** @class */ (() => {
-    class Foo {
-        x = this;
-        static t = this;
-        static at = () => this;
-        static ft = function () { return this; };
-        static mt() { return this; }
-    }
-    return Foo;
-})();
+class Foo {
+    x = this;
+    static t = this;
+    static at = () => this;
+    static ft = function () { return this; };
+    static mt() { return this; }
+}

tests/cases/compiler/addOptimizationHints.ts

@@ -0,0 +1,20 @@
+// @target: ES2015
+// @experimentalDecorators: true
+// @noemithelpers: true
+// @addOptimizationHints: true
+class HasNoStatics {
+  value: unknown;
+  method() {}
+}
+
+class HasStatic {
+  static value = 0;
+  static someMethod() {}
+
+  method() {}
+}
+
+@decorate
+class HasDecorator {
+  method() {}
+}