fix(@ngtools/webpack): also elide type references on transform (#16085)

Fix #14617

Author: filipesilva

packages/ngtools/webpack/src/transformers/elide_imports.ts

@@ -33,8 +33,8 @@ export function elideImports(
   const imports: ts.ImportDeclaration[] = [];
 
   ts.forEachChild(sourceFile, function visit(node) {
-    // Skip removed nodes
-    if (removedNodes.includes(node)) {
+    // Skip type references and removed nodes. We consider both unused.
+    if (node.kind == ts.SyntaxKind.TypeReference || removedNodes.includes(node)) {
       return;
     }
 

packages/ngtools/webpack/src/transformers/elide_imports_spec.ts

@@ -33,6 +33,19 @@ describe('@ngtools/webpack transformers', () => {
       `,
     };
 
+    it('should remove unused imports', () => {
+      const input = tags.stripIndent`
+        import { promise } from './const';
+        import { take } from './const';
+        const unused = promise;
+      `;
+
+      const { program, compilerHost } = createTypescriptContext(input, additionalFiles);
+      const result = transformTypescript(undefined, [transformer(program)], program, compilerHost);
+
+      expect(tags.oneLine`${result}`).toEqual('');
+    });
+
     it('should remove unused aliased imports', () => {
       const input = tags.stripIndent`
         import { promise as fromPromise } from './const';
@@ -188,7 +201,7 @@ describe('@ngtools/webpack transformers', () => {
       expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
     });
 
-    it('should only drop unused default imports when named and default', () => {
+    it('should only drop unused default imports when named and default (1)', () => {
       const input = tags.stripIndent`
         import promise, { promise as fromPromise } from './const';
         const used = fromPromise;
@@ -206,7 +219,7 @@ describe('@ngtools/webpack transformers', () => {
       expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
     });
 
-    it('should only drop unused named imports when named and default', () => {
+    it('should only drop unused named imports when named and default (2)', () => {
       const input = tags.stripIndent`
         import promise, { promise as fromPromise, take } from './const';
         const used = fromPromise;
@@ -224,7 +237,7 @@ describe('@ngtools/webpack transformers', () => {
       expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
     });
 
-    it('should only drop default imports when having named and default', () => {
+    it('should only drop default imports when having named and default (3)', () => {
       const input = tags.stripIndent`
         import promise, { fromPromise } from './const';
         const used = promise;

packages/ngtools/webpack/src/transformers/remove_decorators_spec.ts

@@ -248,5 +248,47 @@ describe('@ngtools/webpack transformers', () => {
 
       expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
     });
+
+    it('should not prevent removal of unused imports', () => {
+      // Note: this is actually testing the behaviour of `./elide_imports.ts`, but the problem
+      // only came up when used together with `./remove_decorators.ts` so we test it here.
+      // Originally reported as https://github.com/angular/angular-cli/issues/14617
+      // The bug happened because `elideImports` would attempt to remove `BigDependency` and
+      // in the process modify the import statement, which then prevented TS from removing it
+      // the interface too.
+      const input = tags.stripIndent`
+        import {BigDependency, BigDependencyOptions} from 'src/app/lorem/big-dependency';
+        import {Injectable} from '@angular/core';
+
+        const bigDependencyLoader = () => import('../lorem/big-dependency');
+
+        @Injectable({providedIn: 'root'})
+        export class LoremService {
+            load(options: BigDependencyOptions): Promise<any> {
+                return bigDependencyLoader()
+                  .then((m: {BigDependency}) => new m.BigDependency().setOptions(options));
+            }
+        }
+
+      `;
+      const output = tags.stripIndent`
+        const bigDependencyLoader = () => import('../lorem/big-dependency');
+        export class LoremService {
+            load(options) {
+                return bigDependencyLoader()
+                    .then((m) => new m.BigDependency().setOptions(options));
+            }
+        }
+      `;
+
+      const { program, compilerHost } = createTypescriptContext(input);
+      const transformer = removeDecorators(
+        () => true,
+        () => program.getTypeChecker(),
+      );
+      const result = transformTypescript(undefined, [transformer], program, compilerHost);
+
+      expect(tags.oneLine`${result}`).toEqual(tags.oneLine`${output}`);
+    });
   });
 });