From d9cc4b0289eaf382782a994a15497e9526c5a4a2 Mon Sep 17 00:00:00 2001
From: Alan Agius <alanagius@google.com>
Date: Thu, 24 Nov 2022 12:21:50 +0000
Subject: [PATCH] fix(@ngtools/webpack): elide unused type references

In the case the import declaration has an unused import we did not properly elide type references when `emitDecoratorMetadata` is disabled.

Closes #24295

(cherry picked from commit 856720b913ec1ba82b96db2d3a61628cb3795f11)
---
 .../webpack/src/transformers/elide_imports.ts | 49 ++++++++++---------
 .../src/transformers/elide_imports_spec.ts    | 40 +++++++++++++++
 2 files changed, 66 insertions(+), 23 deletions(-)

diff --git a/packages/ngtools/webpack/src/transformers/elide_imports.ts b/packages/ngtools/webpack/src/transformers/elide_imports.ts
index babfd93904f5..3c8bed0e944e 100644
--- a/packages/ngtools/webpack/src/transformers/elide_imports.ts
+++ b/packages/ngtools/webpack/src/transformers/elide_imports.ts
@@ -54,31 +54,34 @@ export function elideImports(
       return;
     }
 
-    if (!ts.isTypeReferenceNode(node)) {
-      let symbol: ts.Symbol | undefined;
-      switch (node.kind) {
-        case ts.SyntaxKind.Identifier:
-          const parent = node.parent;
-          if (parent && ts.isShorthandPropertyAssignment(parent)) {
-            const shorthandSymbol = typeChecker.getShorthandAssignmentValueSymbol(parent);
-            if (shorthandSymbol) {
-              symbol = shorthandSymbol;
-            }
-          } else {
-            symbol = typeChecker.getSymbolAtLocation(node);
+    // Type reference imports do not need to be emitted when emitDecoratorMetadata is disabled.
+    if (ts.isTypeReferenceNode(node) && !compilerOptions.emitDecoratorMetadata) {
+      return;
+    }
+
+    let symbol: ts.Symbol | undefined;
+    switch (node.kind) {
+      case ts.SyntaxKind.Identifier:
+        const parent = node.parent;
+        if (parent && ts.isShorthandPropertyAssignment(parent)) {
+          const shorthandSymbol = typeChecker.getShorthandAssignmentValueSymbol(parent);
+          if (shorthandSymbol) {
+            symbol = shorthandSymbol;
           }
-          break;
-        case ts.SyntaxKind.ExportSpecifier:
-          symbol = typeChecker.getExportSpecifierLocalTargetSymbol(node as ts.ExportSpecifier);
-          break;
-        case ts.SyntaxKind.ShorthandPropertyAssignment:
-          symbol = typeChecker.getShorthandAssignmentValueSymbol(node);
-          break;
-      }
+        } else {
+          symbol = typeChecker.getSymbolAtLocation(node);
+        }
+        break;
+      case ts.SyntaxKind.ExportSpecifier:
+        symbol = typeChecker.getExportSpecifierLocalTargetSymbol(node as ts.ExportSpecifier);
+        break;
+      case ts.SyntaxKind.ShorthandPropertyAssignment:
+        symbol = typeChecker.getShorthandAssignmentValueSymbol(node);
+        break;
+    }
 
-      if (symbol) {
-        usedSymbols.add(symbol);
-      }
+    if (symbol) {
+      usedSymbols.add(symbol);
     }
 
     ts.forEachChild(node, visit);
diff --git a/packages/ngtools/webpack/src/transformers/elide_imports_spec.ts b/packages/ngtools/webpack/src/transformers/elide_imports_spec.ts
index 196cbf3b6d8b..9e6a51e80c1b 100644
--- a/packages/ngtools/webpack/src/transformers/elide_imports_spec.ts
+++ b/packages/ngtools/webpack/src/transformers/elide_imports_spec.ts
@@ -66,6 +66,7 @@ describe('@ngtools/webpack transformers', () => {
       `,
       'service.ts': `
         export class Service { }
+        export class Service2 { }
       `,
       'type.ts': `
         export interface OnChanges {
@@ -385,6 +386,45 @@ describe('@ngtools/webpack transformers', () => {
 
         expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
       });
+
+      it('should remove ctor parameter type reference and unused named import from same declaration', () => {
+        const input = tags.stripIndent`
+          import { Decorator } from './decorator';
+          import { Service, Service2 as ServiceUnused } from './service';
+
+          @Decorator()
+          export class Foo {
+            constructor(param: Service) {
+            }
+          }
+
+          ${dummyNode}
+        `;
+
+        const output = tags.stripIndent`
+          import { __decorate } from "tslib";
+          import { Decorator } from './decorator';
+
+          let Foo = class Foo { constructor(param) { } };
+          Foo = __decorate([ Decorator() ], Foo);
+          export { Foo };
+        `;
+
+        const { program, compilerHost } = createTypescriptContext(
+          input,
+          additionalFiles,
+          true,
+          extraCompilerOptions,
+        );
+        const result = transformTypescript(
+          undefined,
+          [transformer(program)],
+          program,
+          compilerHost,
+        );
+
+        expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
+      });
     });
 
     it('keeps jsxFactory imports when configured', () => {