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feat(@angular/ssr): add
modulepreload for lazy-loaded routes
Enhance performance when using SSR by adding `modulepreload` links to lazy-loaded routes. This ensures that the required modules are preloaded in the background, improving the user experience and reducing the time to interactive. Closes angular#26484
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131 changes: 131 additions & 0 deletions
131
packages/angular/build/src/tools/angular/transformers/lazy-routes-transformer.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,131 @@ | ||
| /** | ||
| * @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.dev/license | ||
| */ | ||
|
|
||
| import assert from 'node:assert'; | ||
| import { relative } from 'node:path/posix'; | ||
| import ts from 'typescript'; | ||
|
|
||
| export function lazyRoutesTransformer( | ||
| program: ts.Program, | ||
| compilerHost: ts.CompilerHost, | ||
| ): ts.TransformerFactory<ts.SourceFile> { | ||
| const compilerOptions = program.getCompilerOptions(); | ||
| const moduleResolutionCache = compilerHost.getModuleResolutionCache?.(); | ||
| assert( | ||
| typeof compilerOptions.basePath === 'string', | ||
| 'compilerOptions.basePath should be a string.', | ||
| ); | ||
| const basePath = compilerOptions.basePath; | ||
|
|
||
| return (context: ts.TransformationContext) => { | ||
| const factory = context.factory; | ||
|
|
||
| const visitor = (node: ts.Node): ts.Node => { | ||
| if (!ts.isObjectLiteralExpression(node)) { | ||
| return ts.visitEachChild(node, visitor, context); | ||
| } | ||
|
|
||
| let hasPathProperty = false; | ||
| let loadComponentOrChildrenProperty: ts.PropertyAssignment | undefined; | ||
| for (const prop of node.properties) { | ||
| if (!ts.isPropertyAssignment(prop) || !ts.isIdentifier(prop.name)) { | ||
| continue; | ||
| } | ||
|
|
||
| const propertyNameText = prop.name.text; | ||
| if (propertyNameText === 'path') { | ||
| hasPathProperty = true; | ||
| } else if (propertyNameText === 'loadComponent' || propertyNameText === 'loadChildren') { | ||
| loadComponentOrChildrenProperty = prop; | ||
| } | ||
|
|
||
| if (hasPathProperty && loadComponentOrChildrenProperty) { | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| const initializer = loadComponentOrChildrenProperty?.initializer; | ||
| if ( | ||
| !hasPathProperty || | ||
| !initializer || | ||
| !ts.isArrowFunction(initializer) || | ||
| !ts.isCallExpression(initializer.body) || | ||
| !ts.isPropertyAccessExpression(initializer.body.expression) || | ||
| initializer.body.expression.name.text !== 'then' || | ||
| !ts.isCallExpression(initializer.body.expression.expression) || | ||
| initializer.body.expression.expression.expression.kind !== ts.SyntaxKind.ImportKeyword | ||
| ) { | ||
| return ts.visitEachChild(node, visitor, context); | ||
| } | ||
|
|
||
| const callExpressionArgument = initializer.body.expression.expression.arguments[0]; | ||
| if ( | ||
| !ts.isStringLiteral(callExpressionArgument) && | ||
| !ts.isNoSubstitutionTemplateLiteral(callExpressionArgument) | ||
| ) { | ||
| return ts.visitEachChild(node, visitor, context); | ||
| } | ||
|
|
||
| const resolvedPath = ts.resolveModuleName( | ||
| callExpressionArgument.text, | ||
| node.getSourceFile().fileName, | ||
| compilerOptions, | ||
| compilerHost, | ||
| moduleResolutionCache, | ||
| )?.resolvedModule?.resolvedFileName; | ||
|
|
||
| if (!resolvedPath) { | ||
| return ts.visitEachChild(node, visitor, context); | ||
| } | ||
|
|
||
| const resolvedRelativePath = relative(basePath, resolvedPath); | ||
|
|
||
| // Create the new property | ||
| // Exmaple: `...(typeof ngServerMode !== "undefined" && ngServerMode ? { ɵentryName: "src/home.ts" } : undefined)` | ||
| const newProperty = factory.createSpreadAssignment( | ||
| factory.createParenthesizedExpression( | ||
| factory.createConditionalExpression( | ||
| factory.createBinaryExpression( | ||
| factory.createBinaryExpression( | ||
| factory.createTypeOfExpression(factory.createIdentifier('ngServerMode')), | ||
| factory.createToken(ts.SyntaxKind.ExclamationEqualsEqualsToken), | ||
| factory.createStringLiteral('undefined'), | ||
| ), | ||
| factory.createToken(ts.SyntaxKind.AmpersandAmpersandToken), | ||
| factory.createIdentifier('ngServerMode'), | ||
| ), | ||
| factory.createToken(ts.SyntaxKind.QuestionToken), | ||
| factory.createObjectLiteralExpression( | ||
| [ | ||
| factory.createPropertyAssignment( | ||
| factory.createIdentifier('ɵentryName'), | ||
| factory.createStringLiteral(resolvedRelativePath), | ||
| ), | ||
| ], | ||
| false, | ||
| ), | ||
| factory.createToken(ts.SyntaxKind.ColonToken), | ||
| factory.createIdentifier('undefined'), | ||
| ), | ||
| ), | ||
| ); | ||
|
|
||
| return factory.updateObjectLiteralExpression(node, [...node.properties, newProperty]); | ||
| }; | ||
|
|
||
| return (sourceFile) => { | ||
| const text = sourceFile.text; | ||
| if (!text.includes('loadComponent') && !text.includes('loadChildren')) { | ||
| // Fast check | ||
| return sourceFile; | ||
| } | ||
|
|
||
| return ts.visitEachChild(sourceFile, visitor, context); | ||
| }; | ||
| }; | ||
| } |
121 changes: 121 additions & 0 deletions
121
packages/angular/build/src/tools/angular/transformers/lazy-routes-transformer_spec.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,121 @@ | ||
| /** | ||
| * @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.dev/license | ||
| */ | ||
|
|
||
| import ts from 'typescript'; | ||
| import { lazyRoutesTransformer } from './lazy-routes-transformer'; | ||
|
|
||
| describe('lazyRoutesTransformer', () => { | ||
| let program: ts.Program; | ||
| let compilerHost: ts.CompilerHost; | ||
|
|
||
| beforeEach(() => { | ||
| // Mock a basic TypeScript program and compilerHost | ||
| program = ts.createProgram(['/project/src/dummy.ts'], { basePath: '/project/' }); | ||
| compilerHost = { | ||
| getNewLine: () => '\n', | ||
| fileExists: () => true, | ||
| readFile: () => '', | ||
| writeFile: () => undefined, | ||
| getCanonicalFileName: (fileName: string) => fileName, | ||
| getCurrentDirectory: () => '/project', | ||
| getDefaultLibFileName: () => 'lib.d.ts', | ||
| getSourceFile: () => undefined, | ||
| useCaseSensitiveFileNames: () => true, | ||
| resolveModuleNames: (moduleNames, containingFile) => | ||
| moduleNames.map( | ||
| (name) => | ||
| ({ | ||
| resolvedFileName: `/project/src/${name}.ts`, | ||
| }) as ts.ResolvedModule, | ||
| ), | ||
| }; | ||
| }); | ||
|
|
||
| const transformSourceFile = (sourceCode: string): ts.SourceFile => { | ||
| const sourceFile = ts.createSourceFile( | ||
| '/project/src/dummy.ts', | ||
| sourceCode, | ||
| ts.ScriptTarget.ESNext, | ||
| true, | ||
| ts.ScriptKind.TS, | ||
| ); | ||
|
|
||
| const transformer = lazyRoutesTransformer(program, compilerHost); | ||
| const result = ts.transform(sourceFile, [transformer]); | ||
|
|
||
| return result.transformed[0]; | ||
| }; | ||
|
|
||
| it('should add ɵentryName property to object with loadComponent and path', () => { | ||
| const source = ` | ||
| const routes = [ | ||
| { | ||
| path: 'home', | ||
| loadComponent: () => import('./home').then(m => m.HomeComponent) | ||
| } | ||
| ]; | ||
| `; | ||
|
|
||
| const transformedSourceFile = transformSourceFile(source); | ||
| const transformedCode = ts.createPrinter().printFile(transformedSourceFile); | ||
|
|
||
| expect(transformedCode).toContain( | ||
| `...(typeof ngServerMode !== "undefined" && ngServerMode ? { ɵentryName: "src/home.ts" } : undefined)`, | ||
| ); | ||
| }); | ||
|
|
||
| it('should not modify unrelated object literals', () => { | ||
| const source = ` | ||
| const routes = [ | ||
| { | ||
| path: 'home', | ||
| component: HomeComponent | ||
| } | ||
| ]; | ||
| `; | ||
|
|
||
| const transformedSourceFile = transformSourceFile(source); | ||
| const transformedCode = ts.createPrinter().printFile(transformedSourceFile); | ||
|
|
||
| expect(transformedCode).not.toContain(`ɵentryName`); | ||
| }); | ||
|
|
||
| it('should ignore loadComponent without a valid import call', () => { | ||
| const source = ` | ||
| const routes = [ | ||
| { | ||
| path: 'home', | ||
| loadComponent: () => someFunction() | ||
| } | ||
| ]; | ||
| `; | ||
|
|
||
| const transformedSourceFile = transformSourceFile(source); | ||
| const transformedCode = ts.createPrinter().printFile(transformedSourceFile); | ||
|
|
||
| expect(transformedCode).not.toContain(`ɵentryName`); | ||
| }); | ||
|
|
||
| it('should resolve paths relative to basePath', () => { | ||
| const source = ` | ||
| const routes = [ | ||
| { | ||
| path: 'about', | ||
| loadChildren: () => import('./features/about').then(m => m.AboutModule) | ||
| } | ||
| ]; | ||
| `; | ||
|
|
||
| const transformedSourceFile = transformSourceFile(source); | ||
| const transformedCode = ts.createPrinter().printFile(transformedSourceFile); | ||
|
|
||
| expect(transformedCode).toContain( | ||
| `...(typeof ngServerMode !== "undefined" && ngServerMode ? { ɵentryName: "src/features/about.ts" } : undefined)`, | ||
| ); | ||
| }); | ||
| }); |
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