diff --git a/packages/compiler-cli/ngcc/src/execution/create_compile_function.ts b/packages/compiler-cli/ngcc/src/execution/create_compile_function.ts
index c3671e6946a56..6f8d754ed2670 100644
--- a/packages/compiler-cli/ngcc/src/execution/create_compile_function.ts
+++ b/packages/compiler-cli/ngcc/src/execution/create_compile_function.ts
@@ -14,6 +14,7 @@ import {Logger} from '../../../src/ngtsc/logging';
 import {ParsedConfiguration} from '../../../src/perform_compile';
 import {getEntryPointFormat} from '../packages/entry_point';
 import {makeEntryPointBundle} from '../packages/entry_point_bundle';
+import {createModuleResolutionCache, SharedFileCache} from '../packages/source_file_cache';
 import {PathMappings} from '../path_mappings';
 import {FileWriter} from '../writing/file_writer';
 
@@ -30,6 +31,8 @@ export function getCreateCompileFn(
   return (beforeWritingFiles, onTaskCompleted) => {
     const {Transformer} = require('../packages/transformer');
     const transformer = new Transformer(fileSystem, logger, tsConfig);
+    const sharedFileCache = new SharedFileCache(fileSystem);
+    const moduleResolutionCache = createModuleResolutionCache(fileSystem);
 
     return (task: Task) => {
       const {entryPoint, formatProperty, formatPropertiesToMarkAsProcessed, processDts} = task;
@@ -54,8 +57,8 @@ export function getCreateCompileFn(
       logger.info(`Compiling ${entryPoint.name} : ${formatProperty} as ${format}`);
 
       const bundle = makeEntryPointBundle(
-          fileSystem, entryPoint, formatPath, isCore, format, processDts, pathMappings, true,
-          enableI18nLegacyMessageIdFormat);
+          fileSystem, entryPoint, sharedFileCache, moduleResolutionCache, formatPath, isCore,
+          format, processDts, pathMappings, true, enableI18nLegacyMessageIdFormat);
 
       const result = transformer.transform(bundle);
       if (result.success) {
diff --git a/packages/compiler-cli/ngcc/src/packages/entry_point_bundle.ts b/packages/compiler-cli/ngcc/src/packages/entry_point_bundle.ts
index 68eea9495df18..4acd7f0031de9 100644
--- a/packages/compiler-cli/ngcc/src/packages/entry_point_bundle.ts
+++ b/packages/compiler-cli/ngcc/src/packages/entry_point_bundle.ts
@@ -6,11 +6,12 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-import {AbsoluteFsPath, FileSystem, NgtscCompilerHost} from '../../../src/ngtsc/file_system';
+import {AbsoluteFsPath, FileSystem} from '../../../src/ngtsc/file_system';
 import {PathMappings} from '../path_mappings';
 import {BundleProgram, makeBundleProgram} from './bundle_program';
 import {EntryPoint, EntryPointFormat} from './entry_point';
-import {NgccSourcesCompilerHost} from './ngcc_compiler_host';
+import {NgccDtsCompilerHost, NgccSourcesCompilerHost} from './ngcc_compiler_host';
+import {EntryPointFileCache, SharedFileCache} from './source_file_cache';
 
 /**
  * A bundle of files and paths (and TS programs) that correspond to a particular
@@ -31,6 +32,8 @@ export interface EntryPointBundle {
  * Get an object that describes a formatted bundle for an entry-point.
  * @param fs The current file-system being used.
  * @param entryPoint The entry-point that contains the bundle.
+ * @param sharedFileCache The cache to use for source files that are shared across all entry-points.
+ * @param moduleResolutionCache The module resolution cache to use.
  * @param formatPath The path to the source files for this bundle.
  * @param isCore This entry point is the Angular core package.
  * @param format The underlying format of the bundle.
@@ -42,7 +45,8 @@ export interface EntryPointBundle {
  * component templates.
  */
 export function makeEntryPointBundle(
-    fs: FileSystem, entryPoint: EntryPoint, formatPath: string, isCore: boolean,
+    fs: FileSystem, entryPoint: EntryPoint, sharedFileCache: SharedFileCache,
+    moduleResolutionCache: ts.ModuleResolutionCache, formatPath: string, isCore: boolean,
     format: EntryPointFormat, transformDts: boolean, pathMappings?: PathMappings,
     mirrorDtsFromSrc: boolean = false,
     enableI18nLegacyMessageIdFormat: boolean = true): EntryPointBundle {
@@ -50,8 +54,10 @@ export function makeEntryPointBundle(
   const rootDir = entryPoint.packagePath;
   const options: ts
       .CompilerOptions = {allowJs: true, maxNodeModuleJsDepth: Infinity, rootDir, ...pathMappings};
-  const srcHost = new NgccSourcesCompilerHost(fs, options, entryPoint.packagePath);
-  const dtsHost = new NgtscCompilerHost(fs, options);
+  const entryPointCache = new EntryPointFileCache(fs, sharedFileCache);
+  const dtsHost = new NgccDtsCompilerHost(fs, options, entryPointCache, moduleResolutionCache);
+  const srcHost = new NgccSourcesCompilerHost(
+      fs, options, entryPointCache, moduleResolutionCache, entryPoint.packagePath);
 
   // Create the bundle programs, as necessary.
   const absFormatPath = fs.resolve(entryPoint.path, formatPath);
diff --git a/packages/compiler-cli/ngcc/src/packages/ngcc_compiler_host.ts b/packages/compiler-cli/ngcc/src/packages/ngcc_compiler_host.ts
index 4c5d62f767e3d..c679a12503e94 100644
--- a/packages/compiler-cli/ngcc/src/packages/ngcc_compiler_host.ts
+++ b/packages/compiler-cli/ngcc/src/packages/ngcc_compiler_host.ts
@@ -10,6 +10,7 @@ import * as ts from 'typescript';
 import {AbsoluteFsPath, FileSystem, NgtscCompilerHost} from '../../../src/ngtsc/file_system';
 import {isWithinPackage} from '../analysis/util';
 import {isRelativePath} from '../utils';
+import {EntryPointFileCache} from './source_file_cache';
 
 /**
  * Represents a compiler host that resolves a module import as a JavaScript source file if
@@ -18,19 +19,24 @@ import {isRelativePath} from '../utils';
  * would otherwise let TypeScript prefer the .d.ts file instead of the JavaScript source file.
  */
 export class NgccSourcesCompilerHost extends NgtscCompilerHost {
-  private cache = ts.createModuleResolutionCache(
-      this.getCurrentDirectory(), file => this.getCanonicalFileName(file));
-
-  constructor(fs: FileSystem, options: ts.CompilerOptions, protected packagePath: AbsoluteFsPath) {
+  constructor(
+      fs: FileSystem, options: ts.CompilerOptions, private cache: EntryPointFileCache,
+      private moduleResolutionCache: ts.ModuleResolutionCache,
+      protected packagePath: AbsoluteFsPath) {
     super(fs, options);
   }
 
+  getSourceFile(fileName: string, languageVersion: ts.ScriptTarget): ts.SourceFile|undefined {
+    return this.cache.getCachedSourceFile(fileName, languageVersion);
+  }
+
   resolveModuleNames(
       moduleNames: string[], containingFile: string, reusedNames?: string[],
       redirectedReference?: ts.ResolvedProjectReference): Array<ts.ResolvedModule|undefined> {
     return moduleNames.map(moduleName => {
       const {resolvedModule} = ts.resolveModuleName(
-          moduleName, containingFile, this.options, this, this.cache, redirectedReference);
+          moduleName, containingFile, this.options, this, this.moduleResolutionCache,
+          redirectedReference);
 
       // If the module request originated from a relative import in a JavaScript source file,
       // TypeScript may have resolved the module to its .d.ts declaration file if the .js source
@@ -59,3 +65,31 @@ export class NgccSourcesCompilerHost extends NgtscCompilerHost {
     });
   }
 }
+
+/**
+ * A compiler host implementation that is used for the typings program. It leverages the entry-point
+ * cache for source files and module resolution, as these results can be reused across the sources
+ * program.
+ */
+export class NgccDtsCompilerHost extends NgtscCompilerHost {
+  constructor(
+      fs: FileSystem, options: ts.CompilerOptions, private cache: EntryPointFileCache,
+      private moduleResolutionCache: ts.ModuleResolutionCache) {
+    super(fs, options);
+  }
+
+  getSourceFile(fileName: string, languageVersion: ts.ScriptTarget): ts.SourceFile|undefined {
+    return this.cache.getCachedSourceFile(fileName, languageVersion);
+  }
+
+  resolveModuleNames(
+      moduleNames: string[], containingFile: string, reusedNames?: string[],
+      redirectedReference?: ts.ResolvedProjectReference): Array<ts.ResolvedModule|undefined> {
+    return moduleNames.map(moduleName => {
+      const {resolvedModule} = ts.resolveModuleName(
+          moduleName, containingFile, this.options, this, this.moduleResolutionCache,
+          redirectedReference);
+      return resolvedModule;
+    });
+  }
+}
diff --git a/packages/compiler-cli/ngcc/src/packages/source_file_cache.ts b/packages/compiler-cli/ngcc/src/packages/source_file_cache.ts
new file mode 100644
index 0000000000000..d9b0c33637c25
--- /dev/null
+++ b/packages/compiler-cli/ngcc/src/packages/source_file_cache.ts
@@ -0,0 +1,197 @@
+/**
+ * @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 * as ts from 'typescript';
+import {AbsoluteFsPath, FileSystem} from '../../../src/ngtsc/file_system';
+
+/**
+ * A cache that holds on to source files that can be shared for processing all entry-points in a
+ * single invocation of ngcc. In particular, the following files are shared across all entry-points
+ * through this cache:
+ *
+ * 1. Default library files such as `lib.dom.d.ts` and `lib.es5.d.ts`. These files don't change
+ *    and some are very large, so parsing is expensive. Therefore, the parsed `ts.SourceFile`s for
+ *    the default library files are cached.
+ * 2. The typings of @angular scoped packages. The typing files for @angular packages are typically
+ *    used in the entry-points that ngcc processes, so benefit from a single source file cache.
+ *    Especially `@angular/core/core.d.ts` is large and expensive to parse repeatedly. In contrast
+ *    to default library files, we have to account for these files to be invalidated during a single
+ *    invocation of ngcc, as ngcc will overwrite the .d.ts files during its processing.
+ *
+ * The lifecycle of this cache corresponds with a single invocation of ngcc. Separate invocations,
+ * e.g. the CLI's synchronous module resolution fallback will therefore all have their own cache.
+ * This allows for the source file cache to be garbage collected once ngcc processing has completed.
+ */
+export class SharedFileCache {
+  private sfCache = new Map<AbsoluteFsPath, ts.SourceFile>();
+
+  constructor(private fs: FileSystem) {}
+
+  /**
+   * Loads a `ts.SourceFile` if the provided `fileName` is deemed appropriate to be cached. To
+   * optimize for memory usage, only files that are generally used in all entry-points are cached.
+   * If `fileName` is not considered to benefit from caching or the requested file does not exist,
+   * then `undefined` is returned.
+   */
+  getCachedSourceFile(fileName: string): ts.SourceFile|undefined {
+    const absPath = this.fs.resolve(fileName);
+    if (isDefaultLibrary(absPath, this.fs)) {
+      return this.getStableCachedFile(absPath);
+    } else if (isAngularDts(absPath, this.fs)) {
+      return this.getVolatileCachedFile(absPath);
+    } else {
+      return undefined;
+    }
+  }
+
+  /**
+   * Attempts to load the source file from the cache, or parses the file into a `ts.SourceFile` if
+   * it's not yet cached. This method assumes that the file will not be modified for the duration
+   * that this cache is valid for. If that assumption does not hold, the `getVolatileCachedFile`
+   * method is to be used instead.
+   */
+  private getStableCachedFile(absPath: AbsoluteFsPath): ts.SourceFile|undefined {
+    if (!this.sfCache.has(absPath)) {
+      const content = readFile(absPath, this.fs);
+      if (content === undefined) {
+        return undefined;
+      }
+      const sf = ts.createSourceFile(absPath, content, ts.ScriptTarget.ES2015);
+      this.sfCache.set(absPath, sf);
+    }
+    return this.sfCache.get(absPath)!;
+  }
+
+  /**
+   * In contrast to `getStableCachedFile`, this method always verifies that the cached source file
+   * is the same as what's stored on disk. This is done for files that are expected to change during
+   * ngcc's processing, such as @angular scoped packages for which the .d.ts files are overwritten
+   * by ngcc. If the contents on disk have changed compared to a previously cached source file, the
+   * content from disk is re-parsed and the cache entry is replaced.
+   */
+  private getVolatileCachedFile(absPath: AbsoluteFsPath): ts.SourceFile|undefined {
+    const content = readFile(absPath, this.fs);
+    if (content === undefined) {
+      return undefined;
+    }
+    if (!this.sfCache.has(absPath) || this.sfCache.get(absPath)!.text !== content) {
+      const sf = ts.createSourceFile(absPath, content, ts.ScriptTarget.ES2015);
+      this.sfCache.set(absPath, sf);
+    }
+    return this.sfCache.get(absPath)!;
+  }
+}
+
+const DEFAULT_LIB_PATTERN = ['node_modules', 'typescript', 'lib', /^lib\..+\.d\.ts$/];
+
+/**
+ * Determines whether the provided path corresponds with a default library file inside of the
+ * typescript package.
+ *
+ * @param absPath The path for which to determine if it corresponds with a default library file.
+ * @param fs The filesystem to use for inspecting the path.
+ */
+export function isDefaultLibrary(absPath: AbsoluteFsPath, fs: FileSystem): boolean {
+  return isFile(absPath, DEFAULT_LIB_PATTERN, fs);
+}
+
+const ANGULAR_DTS_PATTERN = ['node_modules', '@angular', /./, /\.d\.ts$/];
+
+/**
+ * Determines whether the provided path corresponds with a .d.ts file inside of an @angular
+ * scoped package. This logic only accounts for the .d.ts files in the root, which is sufficient
+ * to find the large, flattened entry-point files that benefit from caching.
+ *
+ * @param absPath The path for which to determine if it corresponds with an @angular .d.ts file.
+ * @param fs The filesystem to use for inspecting the path.
+ */
+export function isAngularDts(absPath: AbsoluteFsPath, fs: FileSystem): boolean {
+  return isFile(absPath, ANGULAR_DTS_PATTERN, fs);
+}
+
+/**
+ * Helper function to determine whether a file corresponds with a given pattern of segments.
+ *
+ * @param path The path for which to determine if it corresponds with the provided segments.
+ * @param segments Array of segments; the `path` must have ending segments that match the
+ * patterns in this array.
+ * @param fs The filesystem to use for inspecting the path.
+ */
+function isFile(
+    path: AbsoluteFsPath, segments: ReadonlyArray<string|RegExp>, fs: FileSystem): boolean {
+  for (let i = segments.length - 1; i >= 0; i--) {
+    const pattern = segments[i];
+    const segment = fs.basename(path);
+    if (typeof pattern === 'string') {
+      if (pattern !== segment) {
+        return false;
+      }
+    } else {
+      if (!pattern.test(segment)) {
+        return false;
+      }
+    }
+    path = fs.dirname(path);
+  }
+  return true;
+}
+
+/**
+ * A cache for processing a single entry-point. This exists to share `ts.SourceFile`s between the
+ * source and typing programs that are created for a single program.
+ */
+export class EntryPointFileCache {
+  private readonly sfCache = new Map<AbsoluteFsPath, ts.SourceFile>();
+
+  constructor(private fs: FileSystem, private sharedFileCache: SharedFileCache) {}
+
+  /**
+   * Returns and caches a parsed `ts.SourceFile` for the provided `fileName`. If the `fileName` is
+   * cached in the shared file cache, that result is used. Otherwise, the source file is cached
+   * internally. This method returns `undefined` if the requested file does not exist.
+   *
+   * @param fileName The path of the file to retrieve a source file for.
+   * @param languageVersion The language version to use for parsing the file.
+   */
+  getCachedSourceFile(fileName: string, languageVersion: ts.ScriptTarget): ts.SourceFile|undefined {
+    const staticSf = this.sharedFileCache.getCachedSourceFile(fileName);
+    if (staticSf !== undefined) {
+      return staticSf;
+    }
+
+    const absPath = this.fs.resolve(fileName);
+    if (this.sfCache.has(absPath)) {
+      return this.sfCache.get(absPath);
+    }
+
+    const content = readFile(absPath, this.fs);
+    if (content === undefined) {
+      return undefined;
+    }
+    const sf = ts.createSourceFile(fileName, content, languageVersion);
+    this.sfCache.set(absPath, sf);
+    return sf;
+  }
+}
+
+function readFile(absPath: AbsoluteFsPath, fs: FileSystem): string|undefined {
+  if (!fs.exists(absPath) || !fs.stat(absPath).isFile()) {
+    return undefined;
+  }
+  return fs.readFile(absPath);
+}
+
+/**
+ * Creates a `ts.ModuleResolutionCache` that uses the provided filesystem for path operations.
+ *
+ * @param fs The filesystem to use for path operations.
+ */
+export function createModuleResolutionCache(fs: FileSystem): ts.ModuleResolutionCache {
+  return ts.createModuleResolutionCache(fs.pwd(), fileName => {
+    return fs.isCaseSensitive() ? fileName : fileName.toLowerCase();
+  });
+}
diff --git a/packages/compiler-cli/ngcc/test/helpers/utils.ts b/packages/compiler-cli/ngcc/test/helpers/utils.ts
index 75a23805543c5..382758f3c370b 100644
--- a/packages/compiler-cli/ngcc/test/helpers/utils.ts
+++ b/packages/compiler-cli/ngcc/test/helpers/utils.ts
@@ -14,6 +14,7 @@ import {NgccEntryPointConfig} from '../../src/packages/configuration';
 import {EntryPoint, EntryPointFormat} from '../../src/packages/entry_point';
 import {EntryPointBundle} from '../../src/packages/entry_point_bundle';
 import {NgccSourcesCompilerHost} from '../../src/packages/ngcc_compiler_host';
+import {createModuleResolutionCache, EntryPointFileCache, SharedFileCache} from '../../src/packages/source_file_cache';
 
 export type TestConfig = Pick<NgccEntryPointConfig, 'generateDeepReexports'>;
 
@@ -68,7 +69,10 @@ export function makeTestBundleProgram(
   const rootDir = fs.dirname(entryPointPath);
   const options: ts.CompilerOptions =
       {allowJs: true, maxNodeModuleJsDepth: Infinity, checkJs: false, rootDir, rootDirs: [rootDir]};
-  const host = new NgccSourcesCompilerHost(fs, options, rootDir);
+  const moduleResolutionCache = createModuleResolutionCache(fs);
+  const entryPointFileCache = new EntryPointFileCache(fs, new SharedFileCache(fs));
+  const host =
+      new NgccSourcesCompilerHost(fs, options, entryPointFileCache, moduleResolutionCache, rootDir);
   return makeBundleProgram(
       fs, isCore, rootDir, path, 'r3_symbols.js', options, host, additionalFiles);
 }
diff --git a/packages/compiler-cli/ngcc/test/packages/entry_point_bundle_spec.ts b/packages/compiler-cli/ngcc/test/packages/entry_point_bundle_spec.ts
index 8eb133ed0a23a..a5878794af169 100644
--- a/packages/compiler-cli/ngcc/test/packages/entry_point_bundle_spec.ts
+++ b/packages/compiler-cli/ngcc/test/packages/entry_point_bundle_spec.ts
@@ -10,6 +10,7 @@ import {runInEachFileSystem} from '../../../src/ngtsc/file_system/testing';
 import {loadTestFiles} from '../../../test/helpers';
 import {EntryPoint} from '../../src/packages/entry_point';
 import {makeEntryPointBundle} from '../../src/packages/entry_point_bundle';
+import {createModuleResolutionCache, SharedFileCache} from '../../src/packages/source_file_cache';
 
 runInEachFileSystem(() => {
   describe('entry point bundle', () => {
@@ -180,7 +181,10 @@ runInEachFileSystem(() => {
            ignoreMissingDependencies: false,
            generateDeepReexports: false,
          };
-         const esm5bundle = makeEntryPointBundle(fs, entryPoint, './index.js', false, 'esm5', true);
+         const moduleResolutionCache = createModuleResolutionCache(fs);
+         const esm5bundle = makeEntryPointBundle(
+             fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache, './index.js', false,
+             'esm5', true);
 
          expect(esm5bundle.src.program.getSourceFiles().map(sf => sf.fileName))
              .toEqual(jasmine.arrayWithExactContents([
@@ -291,8 +295,11 @@ runInEachFileSystem(() => {
         ignoreMissingDependencies: false,
         generateDeepReexports: false,
       };
+      const moduleResolutionCache = createModuleResolutionCache(fs);
       const esm5bundle = makeEntryPointBundle(
-          fs, entryPoint, './index.js', false, 'esm5', /* transformDts */ true,
+          fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache, './index.js', false,
+          'esm5',
+          /* transformDts */ true,
           /* pathMappings */ undefined, /* mirrorDtsFromSrc */ true);
 
       expect(esm5bundle.src.program.getSourceFiles().map(sf => _(sf.fileName)))
@@ -328,8 +335,11 @@ runInEachFileSystem(() => {
               ignoreMissingDependencies: false,
               generateDeepReexports: false,
             };
+            const moduleResolutionCache = createModuleResolutionCache(fs);
             const esm5bundle = makeEntryPointBundle(
-                fs, entryPoint, './index.js', false, 'esm5', /* transformDts */ true,
+                fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache, './index.js', false,
+                'esm5',
+                /* transformDts */ true,
                 /* pathMappings */ undefined, /* mirrorDtsFromSrc */ true);
             expect(esm5bundle.src.program.getSourceFiles().map(sf => sf.fileName))
                 .toContain(absoluteFrom('/node_modules/test/internal.js'));
@@ -351,8 +361,11 @@ runInEachFileSystem(() => {
               ignoreMissingDependencies: false,
               generateDeepReexports: false,
             };
+            const moduleResolutionCache = createModuleResolutionCache(fs);
             const esm5bundle = makeEntryPointBundle(
-                fs, entryPoint, './esm2015/index.js', false, 'esm2015', /* transformDts */ true,
+                fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache,
+                './esm2015/index.js', false, 'esm2015',
+                /* transformDts */ true,
                 /* pathMappings */ undefined, /* mirrorDtsFromSrc */ true);
             expect(esm5bundle.src.program.getSourceFiles().map(sf => sf.fileName))
                 .toContain(absoluteFrom('/node_modules/internal/esm2015/src/internal.js'));
@@ -374,8 +387,11 @@ runInEachFileSystem(() => {
               ignoreMissingDependencies: false,
               generateDeepReexports: false,
             };
+            const moduleResolutionCache = createModuleResolutionCache(fs);
             const esm5bundle = makeEntryPointBundle(
-                fs, entryPoint, './index.js', false, 'esm5', /* transformDts */ true,
+                fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache, './index.js', false,
+                'esm5',
+                /* transformDts */ true,
                 /* pathMappings */ undefined, /* mirrorDtsFromSrc */ false);
             expect(esm5bundle.src.program.getSourceFiles().map(sf => sf.fileName))
                 .toContain(absoluteFrom('/node_modules/test/internal.js'));
@@ -398,8 +414,11 @@ runInEachFileSystem(() => {
         ignoreMissingDependencies: false,
         generateDeepReexports: false,
       };
+      const moduleResolutionCache = createModuleResolutionCache(fs);
       const bundle = makeEntryPointBundle(
-          fs, entryPoint, './index.js', false, 'esm2015', /* transformDts */ true,
+          fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache, './index.js', false,
+          'esm2015',
+          /* transformDts */ true,
           /* pathMappings */ undefined, /* mirrorDtsFromSrc */ true);
       expect(bundle.rootDirs).toEqual([absoluteFrom('/node_modules/primary')]);
     });
diff --git a/packages/compiler-cli/ngcc/test/packages/source_file_cache_spec.ts b/packages/compiler-cli/ngcc/test/packages/source_file_cache_spec.ts
new file mode 100644
index 0000000000000..8c3ca880897ab
--- /dev/null
+++ b/packages/compiler-cli/ngcc/test/packages/source_file_cache_spec.ts
@@ -0,0 +1,223 @@
+/**
+ * @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 * as ts from 'typescript';
+
+import {absoluteFrom, FileSystem, getFileSystem} from '../../../src/ngtsc/file_system';
+import {runInEachFileSystem} from '../../../src/ngtsc/file_system/testing';
+import {loadTestFiles} from '../../../test/helpers';
+import {EntryPointFileCache, isAngularDts, isDefaultLibrary, SharedFileCache} from '../../src/packages/source_file_cache';
+
+runInEachFileSystem(() => {
+  describe('caching', () => {
+    let _: typeof absoluteFrom;
+    let fs: FileSystem;
+    beforeEach(() => {
+      _ = absoluteFrom;
+      fs = getFileSystem();
+      loadTestFiles([
+        {
+          name: _('/node_modules/typescript/lib/lib.es5.d.ts'),
+          contents: `export declare interface Array {}`,
+        },
+        {
+          name: _('/node_modules/typescript/lib/lib.dom.d.ts'),
+          contents: `export declare interface Window {}`,
+        },
+        {
+          name: _('/node_modules/@angular/core/core.d.ts'),
+          contents: `export declare interface Component {}`,
+        },
+        {
+          name: _('/node_modules/@angular/common/common.d.ts'),
+          contents: `export declare interface NgIf {}`,
+        },
+        {
+          name: _('/index.ts'),
+          contents: `export const index = true;`,
+        },
+        {
+          name: _('/main.ts'),
+          contents: `export const main = true;`,
+        },
+      ]);
+    });
+
+    describe('SharedFileCache', () => {
+      it('should cache a parsed source file for default libraries', () => {
+        const cache = new SharedFileCache(fs);
+
+        const libEs5 = cache.getCachedSourceFile('/node_modules/typescript/lib/lib.es5.d.ts')!;
+        expect(libEs5).not.toBeUndefined();
+        expect(libEs5.text).toContain('Array');
+
+        const libDom = cache.getCachedSourceFile('/node_modules/typescript/lib/lib.dom.d.ts')!;
+        expect(libDom).not.toBeUndefined();
+        expect(libDom.text).toContain('Window');
+
+        const libEs5_2 = cache.getCachedSourceFile('/node_modules/typescript/lib/lib.es5.d.ts')!;
+        expect(libEs5_2).toBe(libEs5);
+
+        const libDom_2 = cache.getCachedSourceFile('/node_modules/typescript/lib/lib.dom.d.ts')!;
+        expect(libDom_2).toBe(libDom);
+      });
+
+      it('should cache a parsed source file for @angular scoped packages', () => {
+        const cache = new SharedFileCache(fs);
+
+        const core = cache.getCachedSourceFile('/node_modules/@angular/core/core.d.ts')!;
+        expect(core).not.toBeUndefined();
+        expect(core.text).toContain('Component');
+
+        const common = cache.getCachedSourceFile('/node_modules/@angular/common/common.d.ts')!;
+        expect(common).not.toBeUndefined();
+        expect(common.text).toContain('NgIf');
+
+        const core_2 = cache.getCachedSourceFile('/node_modules/@angular/core/core.d.ts')!;
+        expect(core_2).toBe(core);
+
+        const common_2 = cache.getCachedSourceFile('/node_modules/@angular/common/common.d.ts')!;
+        expect(common_2).toBe(common);
+      });
+
+      it('should reparse @angular d.ts files when they change', () => {
+        const cache = new SharedFileCache(fs);
+
+        const core = cache.getCachedSourceFile('/node_modules/@angular/core/core.d.ts')!;
+        expect(core).not.toBeUndefined();
+        expect(core.text).toContain('Component');
+
+        const common = cache.getCachedSourceFile('/node_modules/@angular/common/common.d.ts')!;
+        expect(common).not.toBeUndefined();
+        expect(common.text).toContain('NgIf');
+
+        fs.writeFile(
+            _('/node_modules/@angular/core/core.d.ts'), `export declare interface Directive {}`);
+
+        const core_2 = cache.getCachedSourceFile('/node_modules/@angular/core/core.d.ts')!;
+        expect(core_2).not.toBe(core);
+        expect(core_2.text).toContain('Directive');
+
+        const core_3 = cache.getCachedSourceFile('/node_modules/@angular/core/core.d.ts')!;
+        expect(core_3).toBe(core_2);
+
+        const common_2 = cache.getCachedSourceFile('/node_modules/@angular/common/common.d.ts')!;
+        expect(common_2).toBe(common);
+      });
+
+      it('should not cache files that are not default library files inside of the typescript package',
+         () => {
+           const cache = new SharedFileCache(fs);
+
+           expect(cache.getCachedSourceFile('/node_modules/typescript/lib/typescript.d.ts'))
+               .toBeUndefined();
+           expect(cache.getCachedSourceFile('/typescript/lib.es5.d.ts')).toBeUndefined();
+         });
+    });
+
+    describe('isDefaultLibrary()', () => {
+      it('should accept lib files inside of the typescript package', () => {
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/lib.es5.d.ts'), fs)).toBe(true);
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/lib.dom.d.ts'), fs)).toBe(true);
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/lib.es2015.core.d.ts'), fs))
+            .toBe(true);
+        expect(isDefaultLibrary(_('/root/node_modules/typescript/lib/lib.es5.d.ts'), fs))
+            .toBe(true);
+      });
+      it('should reject non lib files inside of the typescript package', () => {
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/typescript.d.ts'), fs)).toBe(false);
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/lib.es5.ts'), fs)).toBe(false);
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib/lib.d.ts'), fs)).toBe(false);
+        expect(isDefaultLibrary(_('/node_modules/typescript/lib.es5.d.ts'), fs)).toBe(false);
+      });
+      it('should reject lib files outside of the typescript package', () => {
+        expect(isDefaultLibrary(_('/node_modules/ttypescript/lib/lib.es5.d.ts'), fs)).toBe(false);
+        expect(isDefaultLibrary(_('/node_modules/ttypescript/lib/lib.es5.d.ts'), fs)).toBe(false);
+        expect(isDefaultLibrary(_('/typescript/lib/lib.es5.d.ts'), fs)).toBe(false);
+      });
+    });
+
+    describe('isAngularDts()', () => {
+      it('should accept .d.ts files inside of the @angular scope', () => {
+        expect(isAngularDts(_('/node_modules/@angular/core/core.d.ts'), fs)).toBe(true);
+        expect(isAngularDts(_('/node_modules/@angular/common/common.d.ts'), fs)).toBe(true);
+      });
+      it('should reject non-.d.ts files inside @angular scoped packages', () => {
+        expect(isAngularDts(_('/node_modules/@angular/common/src/common.ts'), fs)).toBe(false);
+      });
+      it('should reject .d.ts files nested deeply inside @angular scoped packages', () => {
+        expect(isAngularDts(_('/node_modules/@angular/common/src/common.d.ts'), fs)).toBe(false);
+      });
+      it('should reject .d.ts files directly inside the @angular scope', () => {
+        expect(isAngularDts(_('/node_modules/@angular/common.d.ts'), fs)).toBe(false);
+      });
+      it('should reject files that are not inside node_modules', () => {
+        expect(isAngularDts(_('/@angular/core/core.d.ts'), fs)).toBe(false);
+      });
+    });
+
+    describe('EntryPointFileCache', () => {
+      let sharedFileCache: SharedFileCache;
+      beforeEach(() => {
+        sharedFileCache = new SharedFileCache(fs);
+      });
+
+      it('should prefer source files cached in SharedFileCache', () => {
+        const cache1 = new EntryPointFileCache(fs, sharedFileCache);
+        const libEs5_1 = cache1.getCachedSourceFile(
+            '/node_modules/typescript/lib/lib.es5.d.ts', ts.ScriptTarget.ESNext)!;
+        expect(libEs5_1).not.toBeUndefined();
+        expect(libEs5_1.text).toContain('Array');
+        expect(libEs5_1.languageVersion).toBe(ts.ScriptTarget.ES2015);
+
+        const cache2 = new EntryPointFileCache(fs, sharedFileCache);
+        const libEs5_2 = cache2.getCachedSourceFile(
+            '/node_modules/typescript/lib/lib.es5.d.ts', ts.ScriptTarget.ESNext)!;
+        expect(libEs5_1).toBe(libEs5_2);
+      });
+
+      it('should cache source files that are not default library files', () => {
+        const cache = new EntryPointFileCache(fs, sharedFileCache);
+        const index = cache.getCachedSourceFile('/index.ts', ts.ScriptTarget.ESNext)!;
+        expect(index).not.toBeUndefined();
+        expect(index.text).toContain('index');
+        expect(index.languageVersion).toBe(ts.ScriptTarget.ESNext);
+
+        const main = cache.getCachedSourceFile('/main.ts', ts.ScriptTarget.ESNext)!;
+        expect(main).not.toBeUndefined();
+        expect(main.text).toContain('main');
+        expect(main.languageVersion).toBe(ts.ScriptTarget.ESNext);
+
+        const index_2 = cache.getCachedSourceFile('/index.ts', ts.ScriptTarget.ESNext)!;
+        expect(index_2).toBe(index);
+
+        const main_2 = cache.getCachedSourceFile('/main.ts', ts.ScriptTarget.ESNext)!;
+        expect(main_2).toBe(main);
+      });
+
+      it('should not share non-library files across multiple cache instances', () => {
+        const cache1 = new EntryPointFileCache(fs, sharedFileCache);
+        const cache2 = new EntryPointFileCache(fs, sharedFileCache);
+
+        const index1 = cache1.getCachedSourceFile('/index.ts', ts.ScriptTarget.ESNext)!;
+        const index2 = cache2.getCachedSourceFile('/index.ts', ts.ScriptTarget.ESNext)!;
+        expect(index1).not.toBe(index2);
+      });
+
+      it('should return undefined if the file does not exist', () => {
+        const cache = new EntryPointFileCache(fs, sharedFileCache);
+        expect(cache.getCachedSourceFile('/nonexistent.ts', ts.ScriptTarget.ESNext))
+            .toBeUndefined();
+      });
+
+      it('should return undefined if the path is a directory', () => {
+        const cache = new EntryPointFileCache(fs, sharedFileCache);
+        expect(cache.getCachedSourceFile('/node_modules', ts.ScriptTarget.ESNext)).toBeUndefined();
+      });
+    });
+  });
+});
diff --git a/packages/compiler-cli/ngcc/test/writing/new_entry_point_file_writer_spec.ts b/packages/compiler-cli/ngcc/test/writing/new_entry_point_file_writer_spec.ts
index b8fb4aba3382b..255212a20c9d0 100644
--- a/packages/compiler-cli/ngcc/test/writing/new_entry_point_file_writer_spec.ts
+++ b/packages/compiler-cli/ngcc/test/writing/new_entry_point_file_writer_spec.ts
@@ -12,6 +12,7 @@ import {loadTestFiles} from '../../../test/helpers';
 import {NgccConfiguration} from '../../src/packages/configuration';
 import {EntryPoint, EntryPointFormat, EntryPointJsonProperty, getEntryPointInfo, isEntryPoint} from '../../src/packages/entry_point';
 import {EntryPointBundle, makeEntryPointBundle} from '../../src/packages/entry_point_bundle';
+import {createModuleResolutionCache, SharedFileCache} from '../../src/packages/source_file_cache';
 import {FileWriter} from '../../src/writing/file_writer';
 import {NewEntryPointFileWriter} from '../../src/writing/new_entry_point_file_writer';
 import {DirectPackageJsonUpdater} from '../../src/writing/package_json_updater';
@@ -634,7 +635,9 @@ runInEachFileSystem(() => {
   function makeTestBundle(
       fs: FileSystem, entryPoint: EntryPoint, formatProperty: EntryPointJsonProperty,
       format: EntryPointFormat): EntryPointBundle {
+    const moduleResolutionCache = createModuleResolutionCache(fs);
     return makeEntryPointBundle(
-        fs, entryPoint, entryPoint.packageJson[formatProperty]!, false, format, true);
+        fs, entryPoint, new SharedFileCache(fs), moduleResolutionCache,
+        entryPoint.packageJson[formatProperty]!, false, format, true);
   }
 });