Implement the Stage 3 Decorators Proposal (#50820)

Author: rbuckton

src/compiler/_namespaces/ts.ts

@@ -38,6 +38,7 @@ export * from "../transformers/ts";
 export * from "../transformers/classFields";
 export * from "../transformers/typeSerializer";
 export * from "../transformers/legacyDecorators";
+export * from "../transformers/esDecorators";
 export * from "../transformers/es2017";
 export * from "../transformers/es2018";
 export * from "../transformers/es2019";

src/compiler/checker.ts

@@ -218,7 +218,9 @@ const libEntries: [string, string][] = [
     ["esnext.bigint", "lib.es2020.bigint.d.ts"],
     ["esnext.string", "lib.es2022.string.d.ts"],
     ["esnext.promise", "lib.es2021.promise.d.ts"],
-    ["esnext.weakref", "lib.es2021.weakref.d.ts"]
+    ["esnext.weakref", "lib.es2021.weakref.d.ts"],
+    ["decorators", "lib.decorators.d.ts"],
+    ["decorators.legacy", "lib.decorators.legacy.d.ts"],
 ];
 
 /**
@@ -1157,10 +1159,11 @@ const commandOptionsWithoutBuild: CommandLineOption[] = [
     {
         name: "experimentalDecorators",
         type: "boolean",
+        affectsEmit: true,
         affectsSemanticDiagnostics: true,
         affectsBuildInfo: true,
         category: Diagnostics.Language_and_Environment,
-        description: Diagnostics.Enable_experimental_support_for_TC39_stage_2_draft_decorators,
+        description: Diagnostics.Enable_experimental_support_for_legacy_experimental_decorators,
         defaultValueDescription: false,
     },
     {

src/compiler/commandLineParser.ts

@@ -1546,6 +1546,22 @@ export function group<T, K>(values: readonly T[], getGroupId: (value: T) => K, r
     return arrayFrom(arrayToMultiMap(values, getGroupId).values(), resultSelector);
 }
 
+/** @internal */
+export function groupBy<T, U extends T>(values: readonly T[] | undefined, keySelector: (value: T) => value is U): { true?: U[], false?: Exclude<T, U>[] };
+/** @internal */
+export function groupBy<T, K extends string | number | boolean | null | undefined>(values: readonly T[] | undefined, keySelector: (value: T) => K): { [P in K as `${P}`]?: T[]; };
+export function groupBy<T, K extends string | number | boolean | null | undefined>(values: readonly T[] | undefined, keySelector: (value: T) => K): { [P in K as `${P}`]?: T[]; } {
+    const result: Record<string, T[]> = {};
+    if (values) {
+        for (const value of values) {
+            const key = `${keySelector(value)}`;
+            const array = result[key] ??= [];
+            array.push(value);
+        }
+    }
+    return result as { [P in K as `${P}`]?: T[]; };
+}
+
 /** @internal */
 export function clone<T>(object: T): T {
     const result: any = {};
@@ -2822,13 +2838,32 @@ export function padRight(s: string, length: number, padString: " " = " ") {
 /** @internal */
 export function takeWhile<T, U extends T>(array: readonly T[], predicate: (element: T) => element is U): U[];
 /** @internal */
-export function takeWhile<T>(array: readonly T[], predicate: (element: T) => boolean): T[] {
-    const len = array.length;
-    let index = 0;
-    while (index < len && predicate(array[index])) {
-        index++;
+export function takeWhile<T, U extends T>(array: readonly T[] | undefined, predicate: (element: T) => element is U): U[] | undefined;
+export function takeWhile<T, U extends T>(array: readonly T[] | undefined, predicate: (element: T) => element is U): U[] | undefined {
+    if (array) {
+        const len = array.length;
+        let index = 0;
+        while (index < len && predicate(array[index])) {
+            index++;
+        }
+        return array.slice(0, index) as U[];
+    }
+}
+
+/** @internal */
+export function skipWhile<T, U extends T>(array: readonly T[], predicate: (element: T) => element is U): Exclude<T, U>[];
+/** @internal */
+export function skipWhile<T, U extends T>(array: readonly T[] | undefined, predicate: (element: T) => element is U): Exclude<T, U>[] | undefined;
+/** @internal */
+export function skipWhile<T, U extends T>(array: readonly T[] | undefined, predicate: (element: T) => element is U): Exclude<T, U>[] | undefined {
+    if (array) {
+        const len = array.length;
+        let index = 0;
+        while (index < len && predicate(array[index])) {
+            index++;
+        }
+        return array.slice(index) as Exclude<T, U>[];
     }
-    return array.slice(0, index);
 }
 
 /**

src/compiler/core.ts

@@ -687,10 +687,6 @@
         "category": "Error",
         "code": 1218
     },
-    "Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option in your 'tsconfig' or 'jsconfig' to remove this warning.": {
-        "category": "Error",
-        "code": 1219
-    },
     "Generators are not allowed in an ambient context.": {
         "category": "Error",
         "code": 1221
@@ -911,6 +907,14 @@
         "category": "Error",
         "code": 1277
     },
+    "The runtime will invoke the decorator with {1} arguments, but the decorator expects {0}.": {
+        "category": "Error",
+        "code": 1278
+    },
+    "The runtime will invoke the decorator with {1} arguments, but the decorator expects at least {0}.": {
+        "category": "Error",
+        "code": 1279
+    },
 
     "'with' statements are not allowed in an async function block.": {
         "category": "Error",
@@ -1388,7 +1392,7 @@
         "category": "Error",
         "code": 1432
     },
-    "Decorators may not be applied to 'this' parameters.": {
+    "Neither decorators nor modifiers may be applied to 'this' parameters.": {
         "category": "Error",
         "code": 1433
     },
@@ -5655,7 +5659,7 @@
         "category": "Message",
         "code": 6629
     },
-    "Enable experimental support for TC39 stage 2 draft decorators.": {
+    "Enable experimental support for legacy experimental decorators.": {
         "category": "Message",
         "code": 6630
     },
@@ -6488,6 +6492,10 @@
         "category": "Error",
         "code": 8037
     },
+    "Decorators must come after 'export' or 'export default' in JavaScript files.": {
+        "category": "Error",
+        "code": 8038
+    },
 
     "Declaration emit for this file requires using private name '{0}'. An explicit type annotation may unblock declaration emit.": {
         "category": "Error",