refactor(compiler-cli): remove Ivy switch transform (#43891)

Now that the core package has been cleaned up to no longer contain Ivy
switch code, the transform to switch the `PRE_R3` markers to become
`POST_R3` is deleted as well.

PR Close #43891

packages/compiler-cli/src/ngtsc/core/BUILD.bazel

@@ -31,7 +31,6 @@ ts_library(
         "//packages/compiler-cli/src/ngtsc/scope",
         "//packages/compiler-cli/src/ngtsc/shims",
         "//packages/compiler-cli/src/ngtsc/shims:api",
-        "//packages/compiler-cli/src/ngtsc/switch",
         "//packages/compiler-cli/src/ngtsc/transform",
         "//packages/compiler-cli/src/ngtsc/typecheck",
         "//packages/compiler-cli/src/ngtsc/typecheck/api",

packages/compiler-cli/src/ngtsc/core/src/compiler.ts

@@ -25,7 +25,6 @@ import {DeclarationNode, isNamedClassDeclaration, TypeScriptReflectionHost} from
 import {AdapterResourceLoader} from '../../resource';
 import {ComponentScopeReader, LocalModuleScopeRegistry, MetadataDtsModuleScopeResolver, TypeCheckScopeRegistry} from '../../scope';
 import {generatedFactoryTransform} from '../../shims';
-import {ivySwitchTransform} from '../../switch';
 import {aliasTransformFactory, CompilationMode, declarationTransformFactory, DecoratorHandler, DtsTransformRegistry, ivyTransformFactory, TraitCompiler} from '../../transform';
 import {TemplateTypeCheckerImpl} from '../../typecheck';
 import {OptimizeFor, TemplateTypeChecker, TypeCheckingConfig} from '../../typecheck/api';
@@ -647,7 +646,6 @@ export class NgCompiler {
       before.push(
           generatedFactoryTransform(this.adapter.factoryTracker.sourceInfo, importRewriter));
     }
-    before.push(ivySwitchTransform);
 
     return {transformers: {before, afterDeclarations} as ts.CustomTransformers};
   }

packages/compiler-cli/src/ngtsc/switch/BUILD.bazel

@@ -1,14 +0,0 @@
-load("//tools:defaults.bzl", "ts_library")
-
-package(default_visibility = ["//visibility:public"])
-
-ts_library(
-    name = "switch",
-    srcs = ["index.ts"] + glob([
-        "src/**/*.ts",
-    ]),
-    deps = [
-        "//packages/compiler",
-        "@npm//typescript",
-    ],
-)

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

@@ -1,9 +0,0 @@
-/**
- * @license
- * Copyright Google LLC 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
- */
-
-export {ivySwitchTransform} from './src/switch';

packages/compiler-cli/src/ngtsc/switch/src/switch.ts

@@ -1,139 +0,0 @@
-/**
- * @license
- * Copyright Google LLC 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 ts from 'typescript';
-
-const IVY_SWITCH_PRE_SUFFIX = '__PRE_R3__';
-const IVY_SWITCH_POST_SUFFIX = '__POST_R3__';
-
-export function ivySwitchTransform(_: ts.TransformationContext): ts.Transformer<ts.SourceFile> {
-  return flipIvySwitchInFile;
-}
-
-function flipIvySwitchInFile(sf: ts.SourceFile): ts.SourceFile {
-  // To replace the statements array, it must be copied. This only needs to happen if a statement
-  // must actually be replaced within the array, so the newStatements array is lazily initialized.
-  let newStatements: ts.Statement[]|undefined = undefined;
-
-  // Iterate over the statements in the file.
-  for (let i = 0; i < sf.statements.length; i++) {
-    const statement = sf.statements[i];
-
-    // Skip over everything that isn't a variable statement.
-    if (!ts.isVariableStatement(statement) || !hasIvySwitches(statement)) {
-      continue;
-    }
-
-    // This statement needs to be replaced. Check if the newStatements array needs to be lazily
-    // initialized to a copy of the original statements.
-    if (newStatements === undefined) {
-      newStatements = [...sf.statements];
-    }
-
-    // Flip any switches in the VariableStatement. If there were any, a new statement will be
-    // returned; otherwise the old statement will be.
-    newStatements[i] = flipIvySwitchesInVariableStatement(statement, sf.statements);
-  }
-
-  // Only update the statements in the SourceFile if any have changed.
-  if (newStatements !== undefined) {
-    return ts.updateSourceFileNode(sf, newStatements);
-  }
-  return sf;
-}
-
-/**
- * Look for the ts.Identifier of a ts.Declaration with this name.
- *
- * The real identifier is needed (rather than fabricating one) as TypeScript decides how to
- * reference this identifier based on information stored against its node in the AST, which a
- * synthetic node would not have. In particular, since the post-switch variable is often exported,
- * TypeScript needs to know this so it can write `exports.VAR` instead of just `VAR` when emitting
- * code.
- *
- * Only variable, function, and class declarations are currently searched.
- */
-function findPostSwitchIdentifier(
-    statements: ReadonlyArray<ts.Statement>, name: string): ts.Identifier|null {
-  for (const stmt of statements) {
-    if (ts.isVariableStatement(stmt)) {
-      const decl = stmt.declarationList.declarations.find(
-          decl => ts.isIdentifier(decl.name) && decl.name.text === name);
-      if (decl !== undefined) {
-        return decl.name as ts.Identifier;
-      }
-    } else if (ts.isFunctionDeclaration(stmt) || ts.isClassDeclaration(stmt)) {
-      if (stmt.name !== undefined && ts.isIdentifier(stmt.name) && stmt.name.text === name) {
-        return stmt.name;
-      }
-    }
-  }
-  return null;
-}
-
-/**
- * Flip any Ivy switches which are discovered in the given ts.VariableStatement.
- */
-function flipIvySwitchesInVariableStatement(
-    stmt: ts.VariableStatement, statements: ReadonlyArray<ts.Statement>): ts.VariableStatement {
-  // Build a new list of variable declarations. Specific declarations that are initialized to a
-  // pre-switch identifier will be replaced with a declaration initialized to the post-switch
-  // identifier.
-  const newDeclarations = [...stmt.declarationList.declarations];
-  for (let i = 0; i < newDeclarations.length; i++) {
-    const decl = newDeclarations[i];
-
-    // Skip declarations that aren't initialized to an identifier.
-    if (decl.initializer === undefined || !ts.isIdentifier(decl.initializer)) {
-      continue;
-    }
-
-    // Skip declarations that aren't Ivy switches.
-    if (!decl.initializer.text.endsWith(IVY_SWITCH_PRE_SUFFIX)) {
-      continue;
-    }
-
-    // Determine the name of the post-switch variable.
-    const postSwitchName =
-        decl.initializer.text.replace(IVY_SWITCH_PRE_SUFFIX, IVY_SWITCH_POST_SUFFIX);
-
-    // Find the post-switch variable identifier. If one can't be found, it's an error. This is
-    // reported as a thrown error and not a diagnostic as transformers cannot output diagnostics.
-    const newIdentifier = findPostSwitchIdentifier(statements, postSwitchName);
-    if (newIdentifier === null) {
-      throw new Error(`Unable to find identifier ${postSwitchName} in ${
-          stmt.getSourceFile().fileName} for the Ivy switch.`);
-    }
-
-    newDeclarations[i] = ts.updateVariableDeclaration(
-        /* node */ decl,
-        /* name */ decl.name,
-        /* type */ decl.type,
-        /* initializer */ newIdentifier);
-  }
-
-  const newDeclList = ts.updateVariableDeclarationList(
-      /* declarationList */ stmt.declarationList,
-      /* declarations */ newDeclarations);
-
-  const newStmt = ts.updateVariableStatement(
-      /* statement */ stmt,
-      /* modifiers */ stmt.modifiers,
-      /* declarationList */ newDeclList);
-
-  return newStmt;
-}
-
-/**
- * Check whether the given VariableStatement has any Ivy switch variables.
- */
-function hasIvySwitches(stmt: ts.VariableStatement) {
-  return stmt.declarationList.declarations.some(
-      decl => decl.initializer !== undefined && ts.isIdentifier(decl.initializer) &&
-          decl.initializer.text.endsWith(IVY_SWITCH_PRE_SUFFIX));
-}

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -6254,37 +6254,6 @@ function allTests(os: string) {
          });
     });
 
-    describe('ivy switch mode', () => {
-      it('should allow for symbols to be renamed when they use a SWITCH_IVY naming mechanism',
-         () => {
-           env.write('test.ts', `
-export const FooCmp__POST_R3__ = 1;
-export const FooCmp__PRE_R3__ = 2;
-export const FooCmp = FooCmp__PRE_R3__;`);
-           env.driveMain();
-
-           const source = env.getContents('test.js');
-           expect(source).toContain(`export var FooCmp = FooCmp__POST_R3__`);
-           expect(source).not.toContain(`export var FooCmp = FooCmp__PRE_R3__`);
-         });
-
-      it('should allow for SWITCH_IVY naming even even if it occurs outside of core', () => {
-        const content = `
-export const Foo__POST_R3__ = 1;
-export const Foo__PRE_R3__ = 2;
-export const Foo = Foo__PRE_R3__;
-`;
-        env.write('test_outside_angular_core.ts', content);
-        env.write(
-            'test_inside_angular_core.ts', content + '\nexport const ITS_JUST_ANGULAR = true;');
-        env.driveMain();
-
-        const sourceTestOutsideAngularCore = env.getContents('test_outside_angular_core.js');
-        const sourceTestInsideAngularCore = env.getContents('test_inside_angular_core.js');
-        expect(sourceTestInsideAngularCore).toContain(sourceTestOutsideAngularCore);
-      });
-    });
-
     describe('NgModule export aliasing', () => {
       it('should use an alias to import a directive from a deep dependency', () => {
         env.tsconfig({'_useHostForImportGeneration': true});