Add support for constructor parameter decorators (#1439)

aleksander-ciesielski · web-flow · commit 16bde883f98d · 2023-05-05T09:01:30.000+02:00
diff --git a/src/transformation/visitors/class/index.ts b/src/transformation/visitors/class/index.ts
@@ -19,7 +19,11 @@ import {
     transformClassInstanceFields,
     transformStaticPropertyDeclaration,
 } from "./members/fields";
-import { createMethodDecoratingExpression, transformMethodDeclaration } from "./members/method";
+import {
+    createConstructorDecoratingExpression,
+    createMethodDecoratingExpression,
+    transformMethodDeclaration,
+} from "./members/method";
 import { getExtendedNode, getExtendedType, isStaticNode } from "./utils";
 import { createClassSetup } from "./setup";
 import { LuaTarget } from "../../../CompilerOptions";
@@ -116,6 +120,9 @@ function transformClassLikeDeclaration(
         );
 
         if (constructorResult) result.push(constructorResult);
+
+        const decoratingExpression = createConstructorDecoratingExpression(context, constructor, localClassName);
+        if (decoratingExpression) result.push(decoratingExpression);
     } else if (!extendedType) {
         // Generate a constructor if none was defined in a base class
         const constructorResult = transformConstructorDeclaration(
diff --git a/src/transformation/visitors/class/members/method.ts b/src/transformation/visitors/class/members/method.ts
@@ -43,15 +43,11 @@ export function transformMethodDeclaration(
     );
 }
 
-export function createMethodDecoratingExpression(
+export function getParameterDecorators(
     context: TransformationContext,
-    node: ts.MethodDeclaration,
-    className: lua.Identifier
-): lua.Statement | undefined {
-    const methodTable = transformMemberExpressionOwnerName(node, className);
-    const methodName = transformMethodName(context, node);
-
-    const parameterDecorators = node.parameters
+    node: ts.FunctionLikeDeclarationBase
+): lua.CallExpression[] {
+    return node.parameters
         .flatMap((parameter, index) =>
             ts
                 .getDecorators(parameter)
@@ -66,7 +62,30 @@ export function createMethodDecoratingExpression(
                 )
         )
         .filter(isNonNull);
+}
+
+export function createConstructorDecoratingExpression(
+    context: TransformationContext,
+    node: ts.ConstructorDeclaration,
+    className: lua.Identifier
+): lua.Statement | undefined {
+    const parameterDecorators = getParameterDecorators(context, node);
+
+    if (parameterDecorators.length > 0) {
+        const decorateMethod = createDecoratingExpression(context, node.kind, parameterDecorators, className);
+        return lua.createExpressionStatement(decorateMethod);
+    }
+}
+
+export function createMethodDecoratingExpression(
+    context: TransformationContext,
+    node: ts.MethodDeclaration,
+    className: lua.Identifier
+): lua.Statement | undefined {
+    const methodTable = transformMemberExpressionOwnerName(node, className);
+    const methodName = transformMethodName(context, node);
 
+    const parameterDecorators = getParameterDecorators(context, node);
     const methodDecorators = ts.getDecorators(node)?.map(d => transformDecoratorExpression(context, d)) ?? [];
 
     if (methodDecorators.length > 0 || parameterDecorators.length > 0) {
diff --git a/test/unit/classes/decorators.spec.ts b/test/unit/classes/decorators.spec.ts
@@ -142,6 +142,7 @@ test.each([
     ["@decorator static ['evaluated property'];"],
     ["method(@decorator a) {}"],
     ["static method(@decorator a) {}"],
+    ["constructor(@decorator a) {}"],
 ])("Decorate class member (%p)", classMember => {
     util.testFunction`
         let decoratorParameters: any;
