diff --git a/packages/localize/src/tools/src/extract/duplicates.ts b/packages/localize/src/tools/src/extract/duplicates.ts
index dfe1eb6f5e..932bda6ed7 100644
--- a/packages/localize/src/tools/src/extract/duplicates.ts
+++ b/packages/localize/src/tools/src/extract/duplicates.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵMessageId, ɵParsedMessage} from '@angular/localize';
 
 import {DiagnosticHandlingStrategy, Diagnostics} from '../diagnostics';
@@ -17,7 +17,7 @@ import {serializeLocationPosition} from '../source_file_utils';
  * object (as necessary).
  */
 export function checkDuplicateMessages(
-    fs: FileSystem, messages: ɵParsedMessage[],
+    fs: PathManipulation, messages: ɵParsedMessage[],
     duplicateMessageHandling: DiagnosticHandlingStrategy, basePath: AbsoluteFsPath): Diagnostics {
   const diagnostics = new Diagnostics();
   if (duplicateMessageHandling === 'ignore') return diagnostics;
@@ -47,7 +47,7 @@ export function checkDuplicateMessages(
  * Serialize the given `message` object into a string.
  */
 function serializeMessage(
-    fs: FileSystem, basePath: AbsoluteFsPath, message: ɵParsedMessage): string {
+    fs: PathManipulation, basePath: AbsoluteFsPath, message: ɵParsedMessage): string {
   if (message.location === undefined) {
     return `   - "${message.text}"`;
   } else {
diff --git a/packages/localize/src/tools/src/extract/extraction.ts b/packages/localize/src/tools/src/extract/extraction.ts
index ae1644e31a..45144073a0 100644
--- a/packages/localize/src/tools/src/extract/extraction.ts
+++ b/packages/localize/src/tools/src/extract/extraction.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, ReadonlyFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {Logger} from '@angular/compiler-cli/src/ngtsc/logging';
 import {SourceFile, SourceFileLoader} from '@angular/compiler-cli/src/ngtsc/sourcemaps';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
@@ -33,7 +33,7 @@ export class MessageExtractor {
   private loader: SourceFileLoader;
 
   constructor(
-      private fs: FileSystem, private logger: Logger,
+      private fs: ReadonlyFileSystem, private logger: Logger,
       {basePath, useSourceMaps = true, localizeName = '$localize'}: ExtractionOptions) {
     this.basePath = basePath;
     this.useSourceMaps = useSourceMaps;
diff --git a/packages/localize/src/tools/src/extract/main.ts b/packages/localize/src/tools/src/extract/main.ts
index e68335b4ed..6ece99292c 100644
--- a/packages/localize/src/tools/src/extract/main.ts
+++ b/packages/localize/src/tools/src/extract/main.ts
@@ -6,7 +6,7 @@
  * 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 {setFileSystem, NodeJSFileSystem, AbsoluteFsPath, FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {setFileSystem, NodeJSFileSystem, AbsoluteFsPath, FileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ConsoleLogger, Logger, LogLevel} from '@angular/compiler-cli/src/ngtsc/logging';
 import {ɵParsedMessage} from '@angular/localize';
 import * as glob from 'glob';
@@ -214,7 +214,7 @@ export function extractTranslations({
 
 export function getSerializer(
     format: string, sourceLocale: string, rootPath: AbsoluteFsPath, useLegacyIds: boolean,
-    formatOptions: FormatOptions = {}, fs: FileSystem): TranslationSerializer {
+    formatOptions: FormatOptions = {}, fs: PathManipulation): TranslationSerializer {
   switch (format) {
     case 'xlf':
     case 'xlif':
diff --git a/packages/localize/src/tools/src/extract/source_files/es2015_extract_plugin.ts b/packages/localize/src/tools/src/extract/source_files/es2015_extract_plugin.ts
index 646a77b285..70e53e7ba5 100644
--- a/packages/localize/src/tools/src/extract/source_files/es2015_extract_plugin.ts
+++ b/packages/localize/src/tools/src/extract/source_files/es2015_extract_plugin.ts
@@ -5,7 +5,7 @@
  * 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 {FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵparseMessage} from '@angular/localize';
 import {NodePath, PluginObj} from '@babel/core';
 import {TaggedTemplateExpression} from '@babel/types';
@@ -13,7 +13,7 @@ import {TaggedTemplateExpression} from '@babel/types';
 import {getLocation, isGlobalIdentifier, isNamedIdentifier, unwrapExpressionsFromTemplateLiteral, unwrapMessagePartsFromTemplateLiteral} from '../../source_file_utils';
 
 export function makeEs2015ExtractPlugin(
-    fs: FileSystem, messages: ɵParsedMessage[], localizeName = '$localize'): PluginObj {
+    fs: PathManipulation, messages: ɵParsedMessage[], localizeName = '$localize'): PluginObj {
   return {
     visitor: {
       TaggedTemplateExpression(path: NodePath<TaggedTemplateExpression>) {
diff --git a/packages/localize/src/tools/src/extract/source_files/es5_extract_plugin.ts b/packages/localize/src/tools/src/extract/source_files/es5_extract_plugin.ts
index fc83d4ca40..732a102636 100644
--- a/packages/localize/src/tools/src/extract/source_files/es5_extract_plugin.ts
+++ b/packages/localize/src/tools/src/extract/source_files/es5_extract_plugin.ts
@@ -5,7 +5,7 @@
  * 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 {FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵparseMessage} from '@angular/localize';
 import {NodePath, PluginObj} from '@babel/core';
 import {CallExpression} from '@babel/types';
@@ -13,7 +13,7 @@ import {CallExpression} from '@babel/types';
 import {getLocation, isGlobalIdentifier, isNamedIdentifier, unwrapMessagePartsFromLocalizeCall, unwrapSubstitutionsFromLocalizeCall} from '../../source_file_utils';
 
 export function makeEs5ExtractPlugin(
-    fs: FileSystem, messages: ɵParsedMessage[], localizeName = '$localize'): PluginObj {
+    fs: PathManipulation, messages: ɵParsedMessage[], localizeName = '$localize'): PluginObj {
   return {
     visitor: {
       CallExpression(callPath: NodePath<CallExpression>) {
diff --git a/packages/localize/src/tools/src/extract/translation_files/arb_translation_serializer.ts b/packages/localize/src/tools/src/extract/translation_files/arb_translation_serializer.ts
index 5577e675e5..765512a439 100644
--- a/packages/localize/src/tools/src/extract/translation_files/arb_translation_serializer.ts
+++ b/packages/localize/src/tools/src/extract/translation_files/arb_translation_serializer.ts
@@ -5,9 +5,8 @@
  * 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 {AbsoluteFsPath, FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
-import {ArbJsonObject, ArbLocation, ArbMetadata} from '../../translate/translation_files/translation_parsers/arb_translation_parser';
 import {TranslationSerializer} from './translation_serializer';
 import {consolidateMessages, hasLocation} from './utils';
 
@@ -45,7 +44,8 @@ import {consolidateMessages, hasLocation} from './utils';
  */
 export class ArbTranslationSerializer implements TranslationSerializer {
   constructor(
-      private sourceLocale: string, private basePath: AbsoluteFsPath, private fs: FileSystem) {}
+      private sourceLocale: string, private basePath: AbsoluteFsPath,
+      private fs: PathManipulation) {}
 
   serialize(messages: ɵParsedMessage[]): string {
     const messageGroups = consolidateMessages(messages, message => getMessageId(message));
diff --git a/packages/localize/src/tools/src/extract/translation_files/xliff1_translation_serializer.ts b/packages/localize/src/tools/src/extract/translation_files/xliff1_translation_serializer.ts
index b2262c7cb0..a71e211e40 100644
--- a/packages/localize/src/tools/src/extract/translation_files/xliff1_translation_serializer.ts
+++ b/packages/localize/src/tools/src/extract/translation_files/xliff1_translation_serializer.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
 
 import {FormatOptions, validateOptions} from './format_options';
@@ -29,7 +29,7 @@ const LEGACY_XLIFF_MESSAGE_LENGTH = 40;
 export class Xliff1TranslationSerializer implements TranslationSerializer {
   constructor(
       private sourceLocale: string, private basePath: AbsoluteFsPath, private useLegacyIds: boolean,
-      private formatOptions: FormatOptions = {}, private fs: FileSystem = getFileSystem()) {
+      private formatOptions: FormatOptions = {}, private fs: PathManipulation = getFileSystem()) {
     validateOptions('Xliff1TranslationSerializer', [['xml:space', ['preserve']]], formatOptions);
   }
 
diff --git a/packages/localize/src/tools/src/extract/translation_files/xliff2_translation_serializer.ts b/packages/localize/src/tools/src/extract/translation_files/xliff2_translation_serializer.ts
index 9b8b807959..a5a75f7ec5 100644
--- a/packages/localize/src/tools/src/extract/translation_files/xliff2_translation_serializer.ts
+++ b/packages/localize/src/tools/src/extract/translation_files/xliff2_translation_serializer.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
 
 import {FormatOptions, validateOptions} from './format_options';
@@ -29,7 +29,7 @@ export class Xliff2TranslationSerializer implements TranslationSerializer {
   private currentPlaceholderId = 0;
   constructor(
       private sourceLocale: string, private basePath: AbsoluteFsPath, private useLegacyIds: boolean,
-      private formatOptions: FormatOptions = {}, private fs: FileSystem = getFileSystem()) {
+      private formatOptions: FormatOptions = {}, private fs: PathManipulation = getFileSystem()) {
     validateOptions('Xliff1TranslationSerializer', [['xml:space', ['preserve']]], formatOptions);
   }
 
diff --git a/packages/localize/src/tools/src/extract/translation_files/xmb_translation_serializer.ts b/packages/localize/src/tools/src/extract/translation_files/xmb_translation_serializer.ts
index 183c6c6b7b..8cb33981c3 100644
--- a/packages/localize/src/tools/src/extract/translation_files/xmb_translation_serializer.ts
+++ b/packages/localize/src/tools/src/extract/translation_files/xmb_translation_serializer.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
 
 import {extractIcuPlaceholders} from './icu_parsing';
@@ -24,7 +24,7 @@ import {XmlFile} from './xml_file';
 export class XmbTranslationSerializer implements TranslationSerializer {
   constructor(
       private basePath: AbsoluteFsPath, private useLegacyIds: boolean,
-      private fs: FileSystem = getFileSystem()) {}
+      private fs: PathManipulation = getFileSystem()) {}
 
   serialize(messages: ɵParsedMessage[]): string {
     const messageGroups = consolidateMessages(messages, message => this.getMessageId(message));
diff --git a/packages/localize/src/tools/src/source_file_utils.ts b/packages/localize/src/tools/src/source_file_utils.ts
index 9ba2b85837..e0814955e8 100644
--- a/packages/localize/src/tools/src/source_file_utils.ts
+++ b/packages/localize/src/tools/src/source_file_utils.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵisMissingTranslationError, ɵmakeTemplateObject, ɵParsedTranslation, ɵSourceLocation, ɵtranslate} from '@angular/localize';
 import {NodePath} from '@babel/traverse';
 import * as t from '@babel/types';
@@ -74,7 +74,7 @@ export function buildLocalizeReplacement(
  */
 export function unwrapMessagePartsFromLocalizeCall(
     call: NodePath<t.CallExpression>,
-    fs: FileSystem = getFileSystem(),
+    fs: PathManipulation = getFileSystem(),
     ): [TemplateStringsArray, (ɵSourceLocation | undefined)[]] {
   let cooked = call.get('arguments')[0];
 
@@ -160,7 +160,7 @@ export function unwrapMessagePartsFromLocalizeCall(
  */
 export function unwrapSubstitutionsFromLocalizeCall(
     call: NodePath<t.CallExpression>,
-    fs: FileSystem = getFileSystem()): [t.Expression[], (ɵSourceLocation | undefined)[]] {
+    fs: PathManipulation = getFileSystem()): [t.Expression[], (ɵSourceLocation | undefined)[]] {
   const expressions = call.get('arguments').splice(1);
   if (!isArrayOfExpressions(expressions)) {
     const badExpression = expressions.find(expression => !expression.isExpression())!;
@@ -182,8 +182,8 @@ export function unwrapSubstitutionsFromLocalizeCall(
  * @publicApi used by CLI
  */
 export function unwrapMessagePartsFromTemplateLiteral(
-    elements: NodePath<t.TemplateElement>[],
-    fs: FileSystem = getFileSystem()): [TemplateStringsArray, (ɵSourceLocation | undefined)[]] {
+    elements: NodePath<t.TemplateElement>[], fs: PathManipulation = getFileSystem()):
+    [TemplateStringsArray, (ɵSourceLocation | undefined)[]] {
   const cooked = elements.map(q => {
     if (q.node.value.cooked === undefined) {
       throw new BabelParseError(
@@ -207,7 +207,7 @@ export function unwrapMessagePartsFromTemplateLiteral(
  */
 export function unwrapExpressionsFromTemplateLiteral(
     quasi: NodePath<t.TemplateLiteral>,
-    fs: FileSystem = getFileSystem()): [t.Expression[], (ɵSourceLocation | undefined)[]] {
+    fs: PathManipulation = getFileSystem()): [t.Expression[], (ɵSourceLocation | undefined)[]] {
   return [quasi.node.expressions, quasi.get('expressions').map(e => getLocation(fs, e))];
 }
 
@@ -235,7 +235,7 @@ export function wrapInParensIfNecessary(expression: t.Expression): t.Expression
  */
 export function unwrapStringLiteralArray(
     array: NodePath<t.Expression>,
-    fs: FileSystem = getFileSystem()): [string[], (ɵSourceLocation | undefined)[]] {
+    fs: PathManipulation = getFileSystem()): [string[], (ɵSourceLocation | undefined)[]] {
   if (!isStringLiteralArray(array.node)) {
     throw new BabelParseError(
         array.node, 'Unexpected messageParts for `$localize` (expected an array of strings).');
@@ -400,7 +400,7 @@ export function buildCodeFrameError(path: NodePath, e: BabelParseError): string
 }
 
 export function getLocation(
-    fs: FileSystem, startPath: NodePath, endPath?: NodePath): ɵSourceLocation|undefined {
+    fs: PathManipulation, startPath: NodePath, endPath?: NodePath): ɵSourceLocation|undefined {
   const startLocation = startPath.node.loc;
   const file = getFileFromPath(fs, startPath);
   if (!startLocation || !file) {
@@ -425,7 +425,7 @@ export function serializeLocationPosition(location: ɵSourceLocation): string {
   return `${location.start.line + 1}${endLineString}`;
 }
 
-function getFileFromPath(fs: FileSystem, path: NodePath|undefined): AbsoluteFsPath|null {
+function getFileFromPath(fs: PathManipulation, path: NodePath|undefined): AbsoluteFsPath|null {
   const opts = path?.hub.file.opts;
   return opts?.filename ?
       fs.resolve(opts.generatorOpts.sourceRoot ?? opts.cwd, fs.relative(opts.cwd, opts.filename)) :
diff --git a/packages/localize/src/tools/src/translate/source_files/es2015_translate_plugin.ts b/packages/localize/src/tools/src/translate/source_files/es2015_translate_plugin.ts
index f2b351f88c..be1f351361 100644
--- a/packages/localize/src/tools/src/translate/source_files/es2015_translate_plugin.ts
+++ b/packages/localize/src/tools/src/translate/source_files/es2015_translate_plugin.ts
@@ -5,13 +5,12 @@
  * 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 {FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedTranslation} from '@angular/localize';
 import {NodePath, PluginObj} from '@babel/core';
 import {TaggedTemplateExpression} from '@babel/types';
 
 import {Diagnostics} from '../../diagnostics';
-
 import {buildCodeFrameError, buildLocalizeReplacement, isBabelParseError, isLocalize, translate, TranslatePluginOptions, unwrapMessagePartsFromTemplateLiteral} from '../../source_file_utils';
 
 /**
@@ -23,7 +22,7 @@ import {buildCodeFrameError, buildLocalizeReplacement, isBabelParseError, isLoca
 export function makeEs2015TranslatePlugin(
     diagnostics: Diagnostics, translations: Record<string, ɵParsedTranslation>,
     {missingTranslation = 'error', localizeName = '$localize'}: TranslatePluginOptions = {},
-    fs: FileSystem = getFileSystem()): PluginObj {
+    fs: PathManipulation = getFileSystem()): PluginObj {
   return {
     visitor: {
       TaggedTemplateExpression(path: NodePath<TaggedTemplateExpression>) {
diff --git a/packages/localize/src/tools/src/translate/source_files/es5_translate_plugin.ts b/packages/localize/src/tools/src/translate/source_files/es5_translate_plugin.ts
index 33a7066192..6a98ff8729 100644
--- a/packages/localize/src/tools/src/translate/source_files/es5_translate_plugin.ts
+++ b/packages/localize/src/tools/src/translate/source_files/es5_translate_plugin.ts
@@ -5,13 +5,12 @@
  * 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 {FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵParsedTranslation} from '@angular/localize';
 import {NodePath, PluginObj} from '@babel/core';
 import {CallExpression} from '@babel/types';
 
 import {Diagnostics} from '../../diagnostics';
-
 import {buildCodeFrameError, buildLocalizeReplacement, isBabelParseError, isLocalize, translate, TranslatePluginOptions, unwrapMessagePartsFromLocalizeCall, unwrapSubstitutionsFromLocalizeCall} from '../../source_file_utils';
 
 /**
@@ -23,7 +22,7 @@ import {buildCodeFrameError, buildLocalizeReplacement, isBabelParseError, isLoca
 export function makeEs5TranslatePlugin(
     diagnostics: Diagnostics, translations: Record<string, ɵParsedTranslation>,
     {missingTranslation = 'error', localizeName = '$localize'}: TranslatePluginOptions = {},
-    fs: FileSystem = getFileSystem()): PluginObj {
+    fs: PathManipulation = getFileSystem()): PluginObj {
   return {
     visitor: {
       CallExpression(callPath: NodePath<CallExpression>) {
diff --git a/packages/localize/src/tools/src/translate/translation_files/translation_loader.ts b/packages/localize/src/tools/src/translate/translation_files/translation_loader.ts
index 8323c0821a..9a9254a6bc 100644
--- a/packages/localize/src/tools/src/translate/translation_files/translation_loader.ts
+++ b/packages/localize/src/tools/src/translate/translation_files/translation_loader.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, ReadonlyFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {DiagnosticHandlingStrategy, Diagnostics} from '../../diagnostics';
 import {TranslationBundle} from '../translator';
 
@@ -16,7 +16,7 @@ import {ParseAnalysis, TranslationParser} from './translation_parsers/translatio
  */
 export class TranslationLoader {
   constructor(
-      private fs: FileSystem, private translationParsers: TranslationParser<any>[],
+      private fs: ReadonlyFileSystem, private translationParsers: TranslationParser<any>[],
       private duplicateTranslation: DiagnosticHandlingStrategy,
       /** @deprecated */ private diagnostics?: Diagnostics) {}
 
diff --git a/packages/localize/src/tools/src/translate/translator.ts b/packages/localize/src/tools/src/translate/translator.ts
index 6c1d1eb3d6..dd5465a8d7 100644
--- a/packages/localize/src/tools/src/translate/translator.ts
+++ b/packages/localize/src/tools/src/translate/translator.ts
@@ -5,7 +5,7 @@
  * 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 {AbsoluteFsPath, FileSystem, PathSegment} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, PathSegment, ReadonlyFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {ɵMessageId, ɵParsedTranslation} from '@angular/localize';
 
 import {Diagnostics} from '../diagnostics';
@@ -64,7 +64,7 @@ export interface TranslationHandler {
  */
 export class Translator {
   constructor(
-      private fs: FileSystem, private resourceHandlers: TranslationHandler[],
+      private fs: ReadonlyFileSystem, private resourceHandlers: TranslationHandler[],
       private diagnostics: Diagnostics) {}
 
   translateFiles(
diff --git a/packages/localize/src/tools/test/extract/translation_files/arb_translation_serializer_spec.ts b/packages/localize/src/tools/test/extract/translation_files/arb_translation_serializer_spec.ts
index 0616434009..e93925dffa 100644
--- a/packages/localize/src/tools/test/extract/translation_files/arb_translation_serializer_spec.ts
+++ b/packages/localize/src/tools/test/extract/translation_files/arb_translation_serializer_spec.ts
@@ -5,7 +5,7 @@
  * 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 {absoluteFrom, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {absoluteFrom, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {runInEachFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system/testing';
 import {ɵParsedMessage} from '@angular/localize';
 
@@ -14,7 +14,7 @@ import {ArbTranslationSerializer} from '../../../src/extract/translation_files/a
 import {location, mockMessage} from './mock_message';
 
 runInEachFileSystem(() => {
-  let fs: FileSystem;
+  let fs: PathManipulation;
   describe('ArbTranslationSerializer', () => {
     beforeEach(() => {
       fs = getFileSystem();
diff --git a/packages/localize/src/tools/test/extract/translation_files/xmb_translation_serializer_spec.ts b/packages/localize/src/tools/test/extract/translation_files/xmb_translation_serializer_spec.ts
index 1a4593d783..9570e6e376 100644
--- a/packages/localize/src/tools/test/extract/translation_files/xmb_translation_serializer_spec.ts
+++ b/packages/localize/src/tools/test/extract/translation_files/xmb_translation_serializer_spec.ts
@@ -5,7 +5,7 @@
  * 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 {absoluteFrom, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {absoluteFrom, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {runInEachFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system/testing';
 import {ɵParsedMessage, ɵSourceLocation} from '@angular/localize';
 
@@ -14,7 +14,7 @@ import {XmbTranslationSerializer} from '../../../src/extract/translation_files/x
 import {location, mockMessage} from './mock_message';
 
 runInEachFileSystem(() => {
-  let fs: FileSystem;
+  let fs: PathManipulation;
   beforeEach(() => fs = getFileSystem());
   describe('XmbTranslationSerializer', () => {
     [false, true].forEach(useLegacyIds => {
diff --git a/packages/localize/src/tools/test/source_file_utils_spec.ts b/packages/localize/src/tools/test/source_file_utils_spec.ts
index df3db7ede3..1f8421fcd7 100644
--- a/packages/localize/src/tools/test/source_file_utils_spec.ts
+++ b/packages/localize/src/tools/test/source_file_utils_spec.ts
@@ -5,7 +5,7 @@
  * 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 {absoluteFrom, FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {absoluteFrom, getFileSystem, PathManipulation} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {runInEachFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system/testing';
 import {ɵmakeTemplateObject} from '@angular/localize';
 import {NodePath, TransformOptions, transformSync} from '@babel/core';
@@ -16,7 +16,7 @@ import {Expression, Identifier, TaggedTemplateExpression, ExpressionStatement, C
 import {isGlobalIdentifier, isNamedIdentifier, isStringLiteralArray, isArrayOfExpressions, unwrapStringLiteralArray, unwrapMessagePartsFromLocalizeCall, wrapInParensIfNecessary, buildLocalizeReplacement, unwrapSubstitutionsFromLocalizeCall, unwrapMessagePartsFromTemplateLiteral, getLocation} from '../src/source_file_utils';
 
 runInEachFileSystem(() => {
-  let fs: FileSystem;
+  let fs: PathManipulation;
   beforeEach(() => fs = getFileSystem());
   describe('utils', () => {
     describe('isNamedIdentifier()', () => {
diff --git a/packages/localize/src/tools/test/translate/source_files/es2015_translate_plugin_spec.ts b/packages/localize/src/tools/test/translate/source_files/es2015_translate_plugin_spec.ts
index 23a5ed343b..b224924511 100644
--- a/packages/localize/src/tools/test/translate/source_files/es2015_translate_plugin_spec.ts
+++ b/packages/localize/src/tools/test/translate/source_files/es2015_translate_plugin_spec.ts
@@ -5,7 +5,6 @@
  * 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 {FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {runInEachFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system/testing';
 import {ɵcomputeMsgId, ɵparseTranslation} from '@angular/localize';
 import {ɵParsedTranslation} from '@angular/localize/private';
@@ -16,8 +15,6 @@ import {TranslatePluginOptions} from '../../../src/source_file_utils';
 import {makeEs2015TranslatePlugin} from '../../../src/translate/source_files/es2015_translate_plugin';
 
 runInEachFileSystem(() => {
-  let fs: FileSystem;
-  beforeEach(() => fs = getFileSystem());
   describe('makeEs2015Plugin', () => {
     describe('(no translations)', () => {
       it('should transform `$localize` tags with binary expression', () => {
diff --git a/packages/localize/src/tools/test/translate/source_files/es5_translate_plugin_spec.ts b/packages/localize/src/tools/test/translate/source_files/es5_translate_plugin_spec.ts
index 088113f405..c89294b5e8 100644
--- a/packages/localize/src/tools/test/translate/source_files/es5_translate_plugin_spec.ts
+++ b/packages/localize/src/tools/test/translate/source_files/es5_translate_plugin_spec.ts
@@ -5,7 +5,6 @@
  * 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 {FileSystem, getFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {runInEachFileSystem} from '@angular/compiler-cli/src/ngtsc/file_system/testing';
 import {ɵcomputeMsgId, ɵparseTranslation} from '@angular/localize';
 import {ɵParsedTranslation} from '@angular/localize/private';
@@ -16,8 +15,6 @@ import {TranslatePluginOptions} from '../../../src/source_file_utils';
 import {makeEs5TranslatePlugin} from '../../../src/translate/source_files/es5_translate_plugin';
 
 runInEachFileSystem(() => {
-  let fs: FileSystem;
-  beforeEach(() => fs = getFileSystem());
   describe('makeEs5Plugin', () => {
     describe('(no translations)', () => {
       it('should transform `$localize` calls with binary expression', () => {