From b6c4af649505a7d158c7d4c0df4d43270bd29fd7 Mon Sep 17 00:00:00 2001
From: Chuck Jazdzewski <chuckj@google.com>
Date: Thu, 13 Jul 2017 14:25:17 -0700
Subject: [PATCH] feat(compiler-cli): automatically lower lambda expressions in
 metadata

---
 packages/compiler-cli/src/compiler_host.ts    |  10 +-
 .../src/path_mapped_compiler_host.ts          |   2 +-
 packages/compiler-cli/src/transformers/api.ts |   4 +
 .../src/transformers/entry_points.ts          |   8 +
 .../src/transformers/lower_expressions.ts     | 177 ++++++++++++++++++
 .../transformers/module_filename_resolver.ts  |   8 +
 .../compiler-cli/src/transformers/program.ts  |  42 +++--
 packages/compiler-cli/test/ngc_spec.ts        | 118 +++++++++++-
 .../transformers/lower_expressions_spec.ts    | 107 +++++++++++
 9 files changed, 456 insertions(+), 20 deletions(-)
 create mode 100644 packages/compiler-cli/src/transformers/lower_expressions.ts
 create mode 100644 packages/compiler-cli/test/transformers/lower_expressions_spec.ts

diff --git a/packages/compiler-cli/src/compiler_host.ts b/packages/compiler-cli/src/compiler_host.ts
index 04d5083770..e7c5c03954 100644
--- a/packages/compiler-cli/src/compiler_host.ts
+++ b/packages/compiler-cli/src/compiler_host.ts
@@ -25,8 +25,9 @@ export interface CompilerHostContext extends ts.ModuleResolutionHost {
   assumeFileExists(fileName: string): void;
 }
 
+export interface MetadataProvider { getMetadata(source: ts.SourceFile): ModuleMetadata|undefined; }
+
 export class CompilerHost implements AotCompilerHost {
-  protected metadataCollector = new MetadataCollector();
   private isGenDirChildOfRootDir: boolean;
   protected basePath: string;
   private genDir: string;
@@ -39,7 +40,8 @@ export class CompilerHost implements AotCompilerHost {
 
   constructor(
       protected program: ts.Program, protected options: AngularCompilerOptions,
-      protected context: CompilerHostContext, collectorOptions?: CollectorOptions) {
+      protected context: CompilerHostContext, collectorOptions?: CollectorOptions,
+      protected metadataProvider: MetadataProvider = new MetadataCollector()) {
     // normalize the path so that it never ends with '/'.
     this.basePath = path.normalize(path.join(this.options.basePath !, '.')).replace(/\\/g, '/');
     this.genDir = path.normalize(path.join(this.options.genDir !, '.')).replace(/\\/g, '/');
@@ -206,7 +208,7 @@ export class CompilerHost implements AotCompilerHost {
     }
 
     const sf = this.getSourceFile(filePath);
-    const metadata = this.metadataCollector.getMetadata(sf);
+    const metadata = this.metadataProvider.getMetadata(sf);
     return metadata ? [metadata] : [];
   }
 
@@ -245,7 +247,7 @@ export class CompilerHost implements AotCompilerHost {
       v3Metadata.metadata[prop] = v1Metadata.metadata[prop];
     }
 
-    const exports = this.metadataCollector.getMetadata(this.getSourceFile(dtsFilePath));
+    const exports = this.metadataProvider.getMetadata(this.getSourceFile(dtsFilePath));
     if (exports) {
       for (let prop in exports.metadata) {
         if (!v3Metadata.metadata[prop]) {
diff --git a/packages/compiler-cli/src/path_mapped_compiler_host.ts b/packages/compiler-cli/src/path_mapped_compiler_host.ts
index 2463b5b4ee..f17b0a5800 100644
--- a/packages/compiler-cli/src/path_mapped_compiler_host.ts
+++ b/packages/compiler-cli/src/path_mapped_compiler_host.ts
@@ -132,7 +132,7 @@ export class PathMappedCompilerHost extends CompilerHost {
       } else {
         const sf = this.getSourceFile(rootedPath);
         sf.fileName = sf.fileName;
-        const metadata = this.metadataCollector.getMetadata(sf);
+        const metadata = this.metadataProvider.getMetadata(sf);
         return metadata ? [metadata] : [];
       }
     }
diff --git a/packages/compiler-cli/src/transformers/api.ts b/packages/compiler-cli/src/transformers/api.ts
index ea0919c3b5..de1ccc3b9d 100644
--- a/packages/compiler-cli/src/transformers/api.ts
+++ b/packages/compiler-cli/src/transformers/api.ts
@@ -91,6 +91,10 @@ export interface CompilerOptions extends ts.CompilerOptions {
 
   // Whether to enable support for <template> and the template attribute (true by default)
   enableLegacyTemplate?: boolean;
+
+  // Whether to enable lowering expressions lambdas and expressions in a reference value
+  // position.
+  disableExpressionLowering?: boolean;
 }
 
 export interface ModuleFilenameResolver {
diff --git a/packages/compiler-cli/src/transformers/entry_points.ts b/packages/compiler-cli/src/transformers/entry_points.ts
index b55b4c81ad..4e4f5b1721 100644
--- a/packages/compiler-cli/src/transformers/entry_points.ts
+++ b/packages/compiler-cli/src/transformers/entry_points.ts
@@ -1,3 +1,11 @@
+/**
+ * @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 * as ts from 'typescript';
 
 import {CompilerHost, CompilerOptions, Program} from './api';
diff --git a/packages/compiler-cli/src/transformers/lower_expressions.ts b/packages/compiler-cli/src/transformers/lower_expressions.ts
new file mode 100644
index 0000000000..b6bf9dcfca
--- /dev/null
+++ b/packages/compiler-cli/src/transformers/lower_expressions.ts
@@ -0,0 +1,177 @@
+/**
+ * @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 {CollectorOptions, MetadataCollector, MetadataValue, ModuleMetadata} from '@angular/tsc-wrapped';
+import * as ts from 'typescript';
+
+export interface LoweringRequest {
+  kind: ts.SyntaxKind;
+  location: number;
+  end: number;
+  name: string;
+}
+
+export type RequestLocationMap = Map<number, LoweringRequest>;
+
+interface Declaration {
+  name: string;
+  node: ts.Node;
+}
+
+interface DeclarationInsert {
+  declarations: Declaration[];
+  priorTo: ts.Node;
+}
+
+function toMap<T, K>(items: T[], select: (item: T) => K): Map<K, T> {
+  return new Map(items.map<[K, T]>(i => [select(i), i]));
+}
+
+function transformSourceFile(
+    sourceFile: ts.SourceFile, requests: RequestLocationMap,
+    context: ts.TransformationContext): ts.SourceFile {
+  const inserts: DeclarationInsert[] = [];
+
+  // Calculate the range of intersting locations. The transform will only visit nodes in this
+  // range to improve the performance on large files.
+  const locations = Array.from(requests.keys());
+  const min = Math.min(...locations);
+  const max = Math.max(...locations);
+
+  function visitSourceFile(sourceFile: ts.SourceFile): ts.SourceFile {
+    function topLevelStatement(node: ts.Node): ts.Node {
+      const declarations: Declaration[] = [];
+
+      function visitNode(node: ts.Node): ts.Node {
+        const nodeRequest = requests.get(node.pos);
+        if (nodeRequest && nodeRequest.kind == node.kind && nodeRequest.end == node.end) {
+          // This node is requested to be rewritten as a reference to the exported name.
+          // Record that the node needs to be moved to an exported variable with the given name
+          const name = nodeRequest.name;
+          declarations.push({name, node});
+          return ts.createIdentifier(name);
+        }
+        if (node.pos <= max && node.end >= min) return ts.visitEachChild(node, visitNode, context);
+        return node;
+      }
+
+      const result = ts.visitEachChild(node, visitNode, context);
+
+      if (declarations.length) {
+        inserts.push({priorTo: result, declarations})
+      }
+      return result;
+    }
+
+    const traversedSource = ts.visitEachChild(sourceFile, topLevelStatement, context);
+    if (inserts.length) {
+      // Insert the declarations before the rewritten statement that references them.
+      const insertMap = toMap(inserts, i => i.priorTo);
+      const newStatements: ts.Statement[] = [...traversedSource.statements];
+      for (let i = newStatements.length; i >= 0; i--) {
+        const statement = newStatements[i];
+        const insert = insertMap.get(statement);
+        if (insert) {
+          const declarations = insert.declarations.map(
+              i => ts.createVariableDeclaration(
+                  i.name, /* type */ undefined, i.node as ts.Expression));
+          const statement = ts.createVariableStatement(
+              /* modifiers */ undefined,
+              ts.createVariableDeclarationList(declarations, ts.NodeFlags.Const));
+          newStatements.splice(i, 0, statement);
+        }
+      }
+
+      // Insert an exports clause to export the declarations
+      newStatements.push(ts.createExportDeclaration(
+          /* decorators */ undefined,
+          /* modifiers */ undefined,
+          ts.createNamedExports(
+              inserts
+                  .reduce(
+                      (accumulator, insert) => [...accumulator, ...insert.declarations],
+                      [] as Declaration[])
+                  .map(
+                      declaration => ts.createExportSpecifier(
+                          /* propertyName */ undefined, declaration.name)))));
+      return ts.updateSourceFileNode(traversedSource, newStatements);
+    }
+    return traversedSource;
+  }
+
+  return visitSourceFile(sourceFile);
+}
+
+export function getExpressionLoweringTransformFactory(requestsMap: RequestsMap):
+    (context: ts.TransformationContext) => (sourceFile: ts.SourceFile) => ts.SourceFile {
+  // Return the factory
+  return (context: ts.TransformationContext) => (sourceFile: ts.SourceFile): ts.SourceFile => {
+    const requests = requestsMap.getRequests(sourceFile);
+    if (requests && requests.size) {
+      return transformSourceFile(sourceFile, requests, context)
+    }
+    return sourceFile;
+  };
+}
+
+export interface RequestsMap { getRequests(sourceFile: ts.SourceFile): RequestLocationMap; }
+
+interface MetadataAndLoweringRequests {
+  metadata: ModuleMetadata|undefined;
+  requests: RequestLocationMap;
+}
+
+export class LowerMetadataCache implements RequestsMap {
+  private collector: MetadataCollector;
+  private metadataCache = new Map<string, MetadataAndLoweringRequests>();
+
+  constructor(options: CollectorOptions, private strict?: boolean) {
+    this.collector = new MetadataCollector(options);
+  }
+
+  getMetadata(sourceFile: ts.SourceFile): ModuleMetadata|undefined {
+    return this.ensureMetadataAndRequests(sourceFile).metadata;
+  }
+
+  getRequests(sourceFile: ts.SourceFile): RequestLocationMap {
+    return this.ensureMetadataAndRequests(sourceFile).requests;
+  }
+
+  private ensureMetadataAndRequests(sourceFile: ts.SourceFile): MetadataAndLoweringRequests {
+    let result = this.metadataCache.get(sourceFile.fileName);
+    if (!result) {
+      result = this.getMetadataAndRequests(sourceFile);
+      this.metadataCache.set(sourceFile.fileName, result);
+    }
+    return result;
+  }
+
+  private getMetadataAndRequests(sourceFile: ts.SourceFile): MetadataAndLoweringRequests {
+    let identNumber = 0;
+    const freshIdent = () => '\u0275' + identNumber++;
+    const requests = new Map<number, LoweringRequest>();
+    const replaceNode =
+        (node: ts.Node) => {
+          const name = freshIdent();
+          requests.set(node.pos, {name, kind: node.kind, location: node.pos, end: node.end});
+          return {__symbolic: 'reference', name};
+        }
+
+    const substituteExpression = (value: MetadataValue, node: ts.Node): MetadataValue => {
+      if (node.kind === ts.SyntaxKind.ArrowFunction ||
+          node.kind === ts.SyntaxKind.FunctionExpression) {
+        return replaceNode(node);
+      }
+      return value;
+    };
+
+    const metadata = this.collector.getMetadata(sourceFile, this.strict, substituteExpression);
+
+    return {metadata, requests};
+  }
+}
\ No newline at end of file
diff --git a/packages/compiler-cli/src/transformers/module_filename_resolver.ts b/packages/compiler-cli/src/transformers/module_filename_resolver.ts
index 9c224d85de..1573f781c2 100644
--- a/packages/compiler-cli/src/transformers/module_filename_resolver.ts
+++ b/packages/compiler-cli/src/transformers/module_filename_resolver.ts
@@ -1,3 +1,11 @@
+/**
+ * @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 * as path from 'path';
 import * as ts from 'typescript';
 
diff --git a/packages/compiler-cli/src/transformers/program.ts b/packages/compiler-cli/src/transformers/program.ts
index 17b5d34024..4e56cbeca0 100644
--- a/packages/compiler-cli/src/transformers/program.ts
+++ b/packages/compiler-cli/src/transformers/program.ts
@@ -17,6 +17,7 @@ import {TypeChecker} from '../diagnostics/check_types';
 
 import {CompilerHost, CompilerOptions, DiagnosticCategory} from './api';
 import {Diagnostic, EmitFlags, Program} from './api';
+import {LowerMetadataCache, getExpressionLoweringTransformFactory} from './lower_expressions';
 import {getAngularEmitterTransformFactory} from './node_emitter_transform';
 
 const GENERATED_FILES = /\.ngfactory\.js$|\.ngstyle\.js$|\.ngsummary\.js$/;
@@ -35,7 +36,7 @@ class AngularCompilerProgram implements Program {
   private aotCompilerHost: AotCompilerHost;
   private compiler: AotCompiler;
   private srcNames: string[];
-  private collector: MetadataCollector;
+  private metadataCache: LowerMetadataCache;
   // Lazily initialized fields
   private _analyzedModules: NgAnalyzedModules|undefined;
   private _structuralDiagnostics: Diagnostic[] = [];
@@ -55,13 +56,14 @@ class AngularCompilerProgram implements Program {
 
     this.tsProgram = ts.createProgram(rootNames, options, host, this.oldTsProgram);
     this.srcNames = this.tsProgram.getSourceFiles().map(sf => sf.fileName);
-    this.aotCompilerHost = new AotCompilerHost(this.tsProgram, options, host);
+    this.metadataCache = new LowerMetadataCache({quotedNames: true}, !!options.strictMetadataEmit);
+    this.aotCompilerHost = new AotCompilerHost(
+        this.tsProgram, options, host, /* collectorOptions */ undefined, this.metadataCache);
     if (host.readResource) {
       this.aotCompilerHost.loadResource = host.readResource.bind(host);
     }
     const {compiler} = createAotCompiler(this.aotCompilerHost, options);
     this.compiler = compiler;
-    this.collector = new MetadataCollector({quotedNames: true});
   }
 
   // Program implementation
@@ -118,11 +120,9 @@ class AngularCompilerProgram implements Program {
     const emitMap = new Map<string, string>();
     const result = this.programWithStubs.emit(
         /* targetSourceFile */ undefined,
-        createWriteFileCallback(emitFlags, this.host, this.collector, this.options, emitMap),
-        cancellationToken, (emitFlags & (EmitFlags.DTS | EmitFlags.JS)) == EmitFlags.DTS, {
-          after: this.options.skipTemplateCodegen ? [] : [getAngularEmitterTransformFactory(
-                                                             this.generatedFiles)]
-        });
+        createWriteFileCallback(emitFlags, this.host, this.metadataCache, emitMap),
+        cancellationToken, (emitFlags & (EmitFlags.DTS | EmitFlags.JS)) == EmitFlags.DTS,
+        this.calculateTransforms());
 
     this.generatedFiles.forEach(file => {
       if (file.source && file.source.length && SUMMARY_JSON_FILES.test(file.genFileUrl)) {
@@ -184,6 +184,21 @@ class AngularCompilerProgram implements Program {
     return this.generatedFiles && this._generatedFileDiagnostics !;
   }
 
+  private calculateTransforms(): ts.CustomTransformers {
+    const before: ts.TransformerFactory<ts.SourceFile>[] = [];
+    const after: ts.TransformerFactory<ts.SourceFile>[] = [];
+    if (!this.options.disableExpressionLowering) {
+      before.push(getExpressionLoweringTransformFactory(this.metadataCache));
+    }
+    if (!this.options.skipTemplateCodegen) {
+      after.push(getAngularEmitterTransformFactory(this.generatedFiles));
+    }
+    const result: ts.CustomTransformers = {};
+    if (before.length) result.before = before;
+    if (after.length) result.after = after;
+    return result;
+  }
+
   private catchAnalysisError(e: any): NgAnalyzedModules {
     if (isSyntaxError(e)) {
       const parserErrors = getParseErrors(e);
@@ -257,8 +272,7 @@ export function createProgram(
 }
 
 function writeMetadata(
-    emitFilePath: string, sourceFile: ts.SourceFile, collector: MetadataCollector,
-    ngOptions: CompilerOptions) {
+    emitFilePath: string, sourceFile: ts.SourceFile, metadataCache: LowerMetadataCache) {
   if (/\.js$/.test(emitFilePath)) {
     const path = emitFilePath.replace(/\.js$/, '.metadata.json');
 
@@ -271,7 +285,7 @@ function writeMetadata(
       collectableFile = (collectableFile as any).original;
     }
 
-    const metadata = collector.getMetadata(collectableFile, !!ngOptions.strictMetadataEmit);
+    const metadata = metadataCache.getMetadata(collectableFile);
     if (metadata) {
       const metadataText = JSON.stringify([metadata]);
       writeFileSync(path, metadataText, {encoding: 'utf-8'});
@@ -280,8 +294,8 @@ function writeMetadata(
 }
 
 function createWriteFileCallback(
-    emitFlags: EmitFlags, host: ts.CompilerHost, collector: MetadataCollector,
-    ngOptions: CompilerOptions, emitMap: Map<string, string>) {
+    emitFlags: EmitFlags, host: ts.CompilerHost, metadataCache: LowerMetadataCache,
+    emitMap: Map<string, string>) {
   const withMetadata =
       (fileName: string, data: string, writeByteOrderMark: boolean,
        onError?: (message: string) => void, sourceFiles?: ts.SourceFile[]) => {
@@ -291,7 +305,7 @@ function createWriteFileCallback(
         }
         if (!generatedFile && sourceFiles && sourceFiles.length == 1) {
           emitMap.set(sourceFiles[0].fileName, fileName);
-          writeMetadata(fileName, sourceFiles[0], collector, ngOptions);
+          writeMetadata(fileName, sourceFiles[0], metadataCache);
         }
       };
   const withoutMetadata =
diff --git a/packages/compiler-cli/test/ngc_spec.ts b/packages/compiler-cli/test/ngc_spec.ts
index 2c272d0c96..0356f00776 100644
--- a/packages/compiler-cli/test/ngc_spec.ts
+++ b/packages/compiler-cli/test/ngc_spec.ts
@@ -308,7 +308,6 @@ describe('ngc command-line', () => {
 
       const exitCode = main(['-p', path.join(basePath, 'tsconfig.json')]);
       expect(exitCode).toEqual(0);
-
       expect(fs.existsSync(path.resolve(outDir, 'mymodule.ngfactory.js'))).toBe(true);
       expect(fs.existsSync(path.resolve(
                  outDir, 'node_modules', '@angular', 'core', 'src',
@@ -316,6 +315,123 @@ describe('ngc command-line', () => {
           .toBe(true);
     });
 
+    describe('expression lowering', () => {
+      beforeEach(() => {
+        writeConfig(`{
+            "extends": "./tsconfig-base.json",
+            "files": ["mymodule.ts"]
+          }`);
+      });
+
+      function compile(): number {
+        const errors: string[] = [];
+        const result = main(['-p', path.join(basePath, 'tsconfig.json')], s => errors.push(s));
+        expect(errors).toEqual([]);
+        return result;
+      }
+
+      it('should be able to lower a lambda expression in a provider', () => {
+        write('mymodule.ts', `
+          import {CommonModule} from '@angular/common';
+          import {NgModule} from '@angular/core';
+
+          class Foo {}
+
+          @NgModule({
+            imports: [CommonModule],
+            providers: [{provide: 'someToken', useFactory: () => new Foo()}]
+          })
+          export class MyModule {}
+        `);
+        expect(compile()).toEqual(0);
+
+        const mymodulejs = path.resolve(outDir, 'mymodule.js');
+        const mymoduleSource = fs.readFileSync(mymodulejs, 'utf8');
+        expect(mymoduleSource).toContain('var ɵ0 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('export { ɵ0');
+
+        const mymodulefactory = path.resolve(outDir, 'mymodule.ngfactory.js');
+        const mymodulefactorySource = fs.readFileSync(mymodulefactory, 'utf8');
+        expect(mymodulefactorySource).toContain('"someToken", i1.ɵ0');
+      });
+
+      it('should be able to lower a function expression in a provider', () => {
+        write('mymodule.ts', `
+          import {CommonModule} from '@angular/common';
+          import {NgModule} from '@angular/core';
+
+          class Foo {}
+
+          @NgModule({
+            imports: [CommonModule],
+            providers: [{provide: 'someToken', useFactory: function() {return new Foo();}}]
+          })
+          export class MyModule {}
+        `);
+        expect(compile()).toEqual(0);
+
+        const mymodulejs = path.resolve(outDir, 'mymodule.js');
+        const mymoduleSource = fs.readFileSync(mymodulejs, 'utf8');
+        expect(mymoduleSource).toContain('var ɵ0 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('export { ɵ0');
+
+        const mymodulefactory = path.resolve(outDir, 'mymodule.ngfactory.js');
+        const mymodulefactorySource = fs.readFileSync(mymodulefactory, 'utf8');
+        expect(mymodulefactorySource).toContain('"someToken", i1.ɵ0');
+      });
+
+      it('should able to lower multiple expressions', () => {
+        write('mymodule.ts', `
+          import {CommonModule} from '@angular/common';
+          import {NgModule} from '@angular/core';
+
+          class Foo {}
+
+          @NgModule({
+            imports: [CommonModule],
+            providers: [
+              {provide: 'someToken', useFactory: () => new Foo()},
+              {provide: 'someToken', useFactory: () => new Foo()},
+              {provide: 'someToken', useFactory: () => new Foo()},
+              {provide: 'someToken', useFactory: () => new Foo()}
+            ]
+          })
+          export class MyModule {}
+        `);
+        expect(compile()).toEqual(0);
+        const mymodulejs = path.resolve(outDir, 'mymodule.js');
+        const mymoduleSource = fs.readFileSync(mymodulejs, 'utf8');
+        expect(mymoduleSource).toContain('ɵ0 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('ɵ1 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('ɵ2 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('ɵ3 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('export { ɵ0, ɵ1, ɵ2, ɵ3');
+      });
+
+      it('should be able to lower an indirect expression', () => {
+        write('mymodule.ts', `
+          import {CommonModule} from '@angular/common';
+          import {NgModule} from '@angular/core';
+
+          class Foo {}
+
+          const factory = () => new Foo();
+
+          @NgModule({
+            imports: [CommonModule],
+            providers: [{provide: 'someToken', useFactory: factory}]
+          })
+          export class MyModule {}
+        `);
+        expect(compile()).toEqual(0);
+
+        const mymodulejs = path.resolve(outDir, 'mymodule.js');
+        const mymoduleSource = fs.readFileSync(mymodulejs, 'utf8');
+        expect(mymoduleSource).toContain('var ɵ0 = function () { return new Foo(); }');
+        expect(mymoduleSource).toContain('export { ɵ0');
+      });
+    });
+
     const shouldExist = (fileName: string) => {
       if (!fs.existsSync(path.resolve(outDir, fileName))) {
         throw new Error(`Expected ${fileName} to be emitted (outDir: ${outDir})`);
diff --git a/packages/compiler-cli/test/transformers/lower_expressions_spec.ts b/packages/compiler-cli/test/transformers/lower_expressions_spec.ts
new file mode 100644
index 0000000000..7588982b03
--- /dev/null
+++ b/packages/compiler-cli/test/transformers/lower_expressions_spec.ts
@@ -0,0 +1,107 @@
+/**
+ * @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 * as ts from 'typescript';
+
+import {LoweringRequest, RequestLocationMap, getExpressionLoweringTransformFactory} from '../../src/transformers/lower_expressions';
+import {Directory, MockAotContext, MockCompilerHost} from '../mocks';
+
+describe('Expression lowering', () => {
+  it('should be able to lower a simple expression', () => {
+    expect(convert('const a = 1 +◊b: 2◊;')).toBe('const b = 2; const a = 1 + b; export { b };');
+  });
+
+  it('should be able to lower an expression in a decorator', () => {
+    expect(convert(`
+        import {Component} from '@angular/core';
+        
+        @Component({
+          provider: [{provide: 'someToken', useFactory:◊l: () => null◊}]
+        })
+        class MyClass {}
+    `)).toContain('const l = () => null; exports.l = l;');
+  });
+});
+
+function convert(annotatedSource: string) {
+  const annotations: {start: number, length: number, name: string}[] = [];
+  let adjustment = 0;
+  const unannotatedSource = annotatedSource.replace(
+      /◊([a-zA-Z]+):(.*)◊/g,
+      (text: string, name: string, source: string, index: number): string => {
+        annotations.push({start: index + adjustment, length: source.length, name});
+        adjustment -= text.length - source.length;
+        return source;
+      });
+
+  const baseFileName = 'someFile';
+  const moduleName = '/' + baseFileName;
+  const fileName = moduleName + '.ts';
+  const context = new MockAotContext('/', {[baseFileName + '.ts']: unannotatedSource});
+  const host = new MockCompilerHost(context);
+
+  const sourceFile = ts.createSourceFile(
+      fileName, unannotatedSource, ts.ScriptTarget.Latest, /* setParentNodes */ true);
+  const requests = new Map<number, LoweringRequest>();
+
+  for (const annotation of annotations) {
+    const node = findNode(sourceFile, annotation.start, annotation.length);
+    expect(node).toBeDefined();
+    if (node) {
+      const location = node.pos;
+      requests.set(location, {name: annotation.name, kind: node.kind, location, end: node.end});
+    }
+  }
+
+  const program = ts.createProgram(
+      [fileName], {module: ts.ModuleKind.CommonJS, target: ts.ScriptTarget.ES2017}, host);
+  const moduleSourceFile = program.getSourceFile(fileName);
+  const transformers: ts.CustomTransformers = {
+    before: [getExpressionLoweringTransformFactory({
+      getRequests(sourceFile: ts.SourceFile): RequestLocationMap{
+        if (sourceFile.fileName == moduleSourceFile.fileName) {
+          return requests;
+        } else {return new Map();}
+      }
+    })]
+  };
+  let result: string = '';
+  const emitResult = program.emit(
+      moduleSourceFile, (emittedFileName, data, writeByteOrderMark, onError, sourceFiles) => {
+        if (fileName.startsWith(moduleName)) {
+          result = data;
+        }
+      }, undefined, undefined, transformers);
+  return normalizeResult(result);
+};
+
+function findNode(node: ts.Node, start: number, length: number): ts.Node|undefined {
+  function find(node: ts.Node): ts.Node|undefined {
+    if (node.getFullStart() == start && node.getEnd() == start + length) {
+      return node;
+    }
+    if (node.getFullStart() <= start && node.getEnd() >= start + length) {
+      return ts.forEachChild(node, find);
+    }
+  }
+  return ts.forEachChild(node, find);
+}
+
+function normalizeResult(result: string): string {
+  // Remove TypeScript prefixes
+  // Remove new lines
+  // Squish adjacent spaces
+  // Remove prefix and postfix spaces
+  return result.replace('"use strict";', ' ')
+      .replace('exports.__esModule = true;', ' ')
+      .replace('Object.defineProperty(exports, "__esModule", { value: true });', ' ')
+      .replace(/\n/g, ' ')
+      .replace(/ +/g, ' ')
+      .replace(/^ /g, '')
+      .replace(/ $/g, '');
+}