Fix decorator emit regression for static fields (microsoft#44933)

Author: rbuckton

src/compiler/transformers/classFields.ts

@@ -923,7 +923,7 @@ namespace ts {
         function getClassFacts(node: ClassLikeDeclaration) {
             let facts = ClassFacts.None;
             const original = getOriginalNode(node);
-            if (isClassDeclaration(original) && some(original.decorators)) {
+            if (isClassDeclaration(original) && classOrConstructorParameterIsDecorated(original)) {
                 facts |= ClassFacts.ClassWasDecorated;
             }
             for (const member of node.members) {

src/compiler/transformers/ts.ts

@@ -567,35 +567,12 @@ namespace ts {
                 visitLexicalEnvironment(node.statements, sourceElementVisitor, context, /*start*/ 0, alwaysStrict));
         }
 
-        /**
-         * Tests whether we should emit a __decorate call for a class declaration.
-         */
-        function shouldEmitDecorateCallForClass(node: ClassDeclaration) {
-            if (node.decorators && node.decorators.length > 0) {
-                return true;
-            }
-
-            const constructor = getFirstConstructorWithBody(node);
-            if (constructor) {
-                return forEach(constructor.parameters, shouldEmitDecorateCallForParameter);
-            }
-
-            return false;
-        }
-
-        /**
-         * Tests whether we should emit a __decorate call for a parameter declaration.
-         */
-        function shouldEmitDecorateCallForParameter(parameter: ParameterDeclaration) {
-            return parameter.decorators !== undefined && parameter.decorators.length > 0;
-        }
-
         function getClassFacts(node: ClassDeclaration, staticProperties: readonly PropertyDeclaration[]) {
             let facts = ClassFacts.None;
             if (some(staticProperties)) facts |= ClassFacts.HasStaticInitializedProperties;
             const extendsClauseElement = getEffectiveBaseTypeNode(node);
             if (extendsClauseElement && skipOuterExpressions(extendsClauseElement.expression).kind !== SyntaxKind.NullKeyword) facts |= ClassFacts.IsDerivedClass;
-            if (shouldEmitDecorateCallForClass(node)) facts |= ClassFacts.HasConstructorDecorators;
+            if (classOrConstructorParameterIsDecorated(node)) facts |= ClassFacts.HasConstructorDecorators;
             if (childIsDecorated(node)) facts |= ClassFacts.HasMemberDecorators;
             if (isExportOfNamespace(node)) facts |= ClassFacts.IsExportOfNamespace;
             else if (isDefaultExternalModuleExport(node)) facts |= ClassFacts.IsDefaultExternalExport;

src/compiler/utilities.ts

@@ -1868,12 +1868,19 @@ namespace ts {
                 return some((node as ClassDeclaration).members, m => nodeOrChildIsDecorated(m, node, parent!)); // TODO: GH#18217
             case SyntaxKind.MethodDeclaration:
             case SyntaxKind.SetAccessor:
+            case SyntaxKind.Constructor:
                 return some((node as FunctionLikeDeclaration).parameters, p => nodeIsDecorated(p, node, parent!)); // TODO: GH#18217
             default:
                 return false;
         }
     }
 
+    export function classOrConstructorParameterIsDecorated(node: ClassDeclaration): boolean {
+        if (nodeIsDecorated(node)) return true;
+        const constructor = getFirstConstructorWithBody(node);
+        return !!constructor && childIsDecorated(constructor, node);
+    }
+
     export function isJSXTagName(node: Node) {
         const { parent } = node;
         if (parent.kind === SyntaxKind.JsxOpeningElement ||

src/tsserver/nodeServer.ts

@@ -256,7 +256,7 @@ namespace ts.server {
         /* eslint-enable no-restricted-globals */
 
         if (typeof global !== "undefined" && global.gc) {
-            sys.gc = () => global.gc!();
+            sys.gc = () => global.gc?.();
         }
 
         sys.require = (initialDir: string, moduleName: string): RequireResult => {

tests/baselines/reference/decoratorOnClassConstructorParameter5.js

@@ -0,0 +1,23 @@
+//// [decoratorOnClassConstructorParameter5.ts]
+// https://github.com/microsoft/TypeScript/issues/44931
+interface IFoo { }
+declare const IFoo: any;
+class BulkEditPreviewProvider {
+    static readonly Schema = 'vscode-bulkeditpreview';
+    static emptyPreview = { scheme: BulkEditPreviewProvider.Schema };
+    constructor(
+        @IFoo private readonly _modeService: IFoo,
+    ) { }
+}
+
+//// [decoratorOnClassConstructorParameter5.js]
+let BulkEditPreviewProvider = class BulkEditPreviewProvider {
+    constructor(_modeService) {
+        this._modeService = _modeService;
+    }
+};
+BulkEditPreviewProvider.Schema = 'vscode-bulkeditpreview';
+BulkEditPreviewProvider.emptyPreview = { scheme: BulkEditPreviewProvider.Schema };
+BulkEditPreviewProvider = __decorate([
+    __param(0, IFoo)
+], BulkEditPreviewProvider);

tests/cases/conformance/decorators/class/constructor/parameter/decoratorOnClassConstructorParameter5.ts

@@ -0,0 +1,15 @@
+// @target: es2018
+// @experimentalDecorators: true
+// @noEmitHelpers: true
+// @noTypesAndSymbols: true
+
+// https://github.com/microsoft/TypeScript/issues/44931
+interface IFoo { }
+declare const IFoo: any;
+class BulkEditPreviewProvider {
+    static readonly Schema = 'vscode-bulkeditpreview';
+    static emptyPreview = { scheme: BulkEditPreviewProvider.Schema };
+    constructor(
+        @IFoo private readonly _modeService: IFoo,
+    ) { }
+}