feat(ivy): dummy handler for @Pipe to cause decorator removal (#24677)

Currently ngtsc does not compile @Pipe. This has a side effect
of not removing the @Pipe decorator.

This adds a dummy DecoratorHandler that compiles @Pipe into an
empty ngPipeDef. Eventually this will be replaced with a full
implementation, but for now this solution allows compield code
to be tree-shaken properly.

PR Close #24677

packages/compiler-cli/src/ngtsc/annotations/index.ts

@@ -10,4 +10,5 @@ export {ComponentDecoratorHandler} from './src/component';
 export {DirectiveDecoratorHandler} from './src/directive';
 export {InjectableDecoratorHandler} from './src/injectable';
 export {NgModuleDecoratorHandler} from './src/ng_module';
+export {PipeDecoratorHandler} from './src/pipe';
 export {CompilationScope, SelectorScopeRegistry} from './src/selector_scope';

packages/compiler-cli/src/ngtsc/annotations/src/pipe.ts

@@ -0,0 +1,39 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {Expression, ExpressionType, LiteralExpr, R3DependencyMetadata, R3InjectableMetadata, R3ResolvedDependencyType, WrappedNodeExpr, compileInjectable as compileIvyInjectable} from '@angular/compiler';
+import * as ts from 'typescript';
+
+import {Decorator, ReflectionHost} from '../../host';
+import {AnalysisOutput, CompileResult, DecoratorHandler} from '../../transform';
+
+import {isAngularCore} from './util';
+
+export class PipeDecoratorHandler implements DecoratorHandler<string> {
+  constructor(private reflector: ReflectionHost, private isCore: boolean) {}
+
+  detect(decorator: Decorator[]): Decorator|undefined {
+    return decorator.find(
+        decorator => decorator.name === 'Pipe' && (this.isCore || isAngularCore(decorator)));
+  }
+
+  analyze(node: ts.ClassDeclaration, decorator: Decorator): AnalysisOutput<string> {
+    return {
+      analysis: 'test',
+    };
+  }
+
+  compile(node: ts.ClassDeclaration, analysis: string): CompileResult {
+    return {
+      name: 'ngPipeDef',
+      initializer: new LiteralExpr(null),
+      statements: [],
+      type: new ExpressionType(new LiteralExpr(null)),
+    };
+  }
+}