fix: use verbatimModuleSyntax consistently in exports

[christoph-fricke]

The new network-source API is not usable as soon as a project tries to import from msw/experimental. It crashes with a runtime error:

SyntaxError: The requested module './define-network.mjs' does not provide an export named 'DefineNetworkOptions'

This PR fixes the problem by using a type export in src/core/experimental/index.ts to ensure DefineNetworkOptions is stripped from the JS output.

---

I initially tried to prevent such problems in the future by enabling verbatimModule syntax in tsconfig.base.json and fixing multiple TS errors reported by pnpm exec tsc --noEmit -p src/tsconfig.src.json, but it caused strange problems in CI.

Besides this, there appear to be multiple TS errors in the project. Some picked in the editor, some only reported by checking with one of the various TS config files such as pnpm exec tsc --noEmit -p ./tsconfig.test.unit.json. Some source code errors I noticed:

• /src/browser/sources/fallback-http-source.ts
• /src/browser/utils/deserializeRequest.ts
• /src/browser/utils/pruneGetRequestBody.ts

It does not look like the CI finds and reports the errors. Are you aware of these existing TypeScript problems?

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between fb8cda5 and ea26ceb.

📒 Files selected for processing (92)

• src/browser/glossary.ts
• src/browser/setup-worker.ts
• src/browser/sources/service-worker-source.ts
• src/browser/utils/deserializeRequest.ts
• src/core/experimental/define-network.ts
• src/core/experimental/frames/http-frame.test.ts
• src/core/experimental/frames/http-frame.ts
• src/core/experimental/frames/websocket-frame.test.ts
• src/core/experimental/frames/websocket-frame.ts
• src/core/experimental/index.ts
• src/core/experimental/on-unhandled-frame.test.ts
• src/core/experimental/setup-api.ts
• src/core/experimental/sources/interceptor-source.ts
• src/core/graphql.ts
• src/core/handlers/GraphQLHandler.test.ts
• src/core/handlers/GraphQLHandler.ts
• src/core/handlers/HttpHandler.test.ts
• src/core/handlers/HttpHandler.ts
• src/core/handlers/RequestHandler.ts
• src/core/http.ts
• src/core/utils/cookieStore.ts
• src/core/utils/executeHandlers.ts
• src/core/utils/handleRequest.test.ts
• src/core/utils/handleRequest.ts
• src/core/utils/internal/parseGraphQLRequest.test.ts
• src/core/utils/internal/parseMultipartData.ts
• src/core/utils/internal/pipeEvents.ts
• src/core/utils/internal/requestHandlerUtils.ts
• src/core/utils/request/onUnhandledRequest.test.ts
• src/core/ws.ts
• src/core/ws/WebSocketClientManager.test.ts
• src/core/ws/WebSocketClientManager.ts
• src/core/ws/WebSocketIndexedDBClientStore.ts
• src/core/ws/WebSocketMemoryClientStore.ts
• src/core/ws/handleWebSocketEvent.ts
• src/native/index.ts
• src/node/async-handlers-controller.ts
• src/node/setup-server-common.ts
• src/node/setup-server.ts
• test/browser/graphql-api/custom-predicate.test.ts
• test/browser/graphql-api/response-patching.test.ts
• test/browser/msw-api/context/delay.mocks.ts
• test/browser/msw-api/req/passthrough.test.ts
• test/browser/msw-api/setup-worker/fallback-mode/fallback-mode.test.ts
• test/browser/msw-api/setup-worker/life-cycle-events/on.mocks.ts
• test/browser/msw-api/setup-worker/life-cycle-events/removeAllListeners.test.ts
• test/browser/msw-api/setup-worker/life-cycle-events/removeListener.test.ts
• test/browser/msw-api/setup-worker/listHandlers.test.ts
• test/browser/msw-api/setup-worker/resetHandlers.test.ts
• test/browser/msw-api/setup-worker/restoreHandlers.test.ts
• test/browser/msw-api/setup-worker/scenarios/iframe/iframe.test.ts
• test/browser/msw-api/setup-worker/start/error.test.ts
• test/browser/msw-api/setup-worker/start/find-worker.test.ts
• test/browser/msw-api/setup-worker/start/quiet.test.ts
• test/browser/msw-api/setup-worker/start/start.test.ts
• test/browser/msw-api/setup-worker/stop/quiet.test.ts
• test/browser/msw-api/setup-worker/use.test.ts
• test/browser/msw-api/unregister.test.ts
• test/browser/playwright.extend.ts
• test/browser/rest-api/body.mocks.ts
• test/browser/rest-api/request/matching/all.test.ts
• test/browser/rest-api/request/matching/custom-predicate.test.ts
• test/browser/sse-api/sse.client.send.extraneous.test.ts
• test/browser/sse-api/sse.client.send.multiline.test.ts
• test/browser/sse-api/sse.client.send.test.ts
• test/browser/sse-api/sse.quiet.test.ts
• test/browser/sse-api/sse.retry.test.ts
• test/browser/sse-api/sse.server.connect.test.ts
• test/browser/sse-api/sse.use.test.ts
• test/browser/sse-api/sse.with-credentials.test.ts
• test/node/graphql-api/batched-queries.apollo.test.ts
• test/node/graphql-api/batched-queries.batched-execute.test.ts
• test/node/msw-api/setup-server/life-cycle-events/on.node.test.ts
• test/node/msw-api/setup-server/use.node.test.ts
• test/node/rest-api/cookies-inheritance.node.test.ts
• test/node/third-party/axios-error-response.test.ts
• test/support/WebSocketServer.ts
• test/support/environments/vitest-environment-node-websocket.ts
• test/support/graphql.ts
• test/support/utils.ts
• test/support/ws-test-utils.ts
• test/typings/custom-handler.test-d.ts
• test/typings/custom-resolver.test-d.ts
• test/typings/define-network.test-d.ts
• test/typings/graphql-typed-document-node.test-d.ts
• test/typings/graphql-typed-document-string.test-d.ts
• test/typings/http-custom-predicate.test-d.ts
• test/typings/regressions/default-resolver-type.test-d.ts
• test/typings/regressions/request-handler-type.test-d.ts
• test/typings/regressions/response-body-type.test-d.ts
• test/typings/ws.test-d.ts
• tsconfig.base.json

💤 Files with no reviewable changes (1)

• src/browser/utils/deserializeRequest.ts

✅ Files skipped from review due to trivial changes (88)

• src/core/utils/handleRequest.ts
• tsconfig.base.json
• src/core/experimental/define-network.ts
• src/native/index.ts
• test/browser/msw-api/setup-worker/listHandlers.test.ts
• src/core/utils/cookieStore.ts
• test/support/environments/vitest-environment-node-websocket.ts
• test/node/graphql-api/batched-queries.batched-execute.test.ts
• src/core/utils/internal/parseMultipartData.ts
• src/browser/glossary.ts
• src/core/experimental/on-unhandled-frame.test.ts
• test/browser/msw-api/setup-worker/use.test.ts
• test/support/graphql.ts
• src/core/ws/handleWebSocketEvent.ts
• src/core/utils/internal/requestHandlerUtils.ts
• src/core/ws/WebSocketMemoryClientStore.ts
• test/node/third-party/axios-error-response.test.ts
• test/browser/rest-api/body.mocks.ts
• src/core/experimental/sources/interceptor-source.ts
• src/node/async-handlers-controller.ts
• test/browser/graphql-api/response-patching.test.ts
• src/core/ws/WebSocketIndexedDBClientStore.ts
• test/browser/sse-api/sse.use.test.ts
• test/browser/sse-api/sse.server.connect.test.ts
• test/browser/msw-api/context/delay.mocks.ts
• src/core/utils/request/onUnhandledRequest.test.ts
• test/browser/msw-api/setup-worker/restoreHandlers.test.ts
• src/core/experimental/frames/websocket-frame.ts
• test/node/msw-api/setup-server/use.node.test.ts
• src/core/http.ts
• test/browser/msw-api/setup-worker/life-cycle-events/on.mocks.ts
• test/browser/msw-api/setup-worker/start/start.test.ts
• test/support/WebSocketServer.ts
• test/typings/graphql-typed-document-node.test-d.ts
• test/browser/rest-api/request/matching/all.test.ts
• test/node/rest-api/cookies-inheritance.node.test.ts
• test/typings/regressions/default-resolver-type.test-d.ts
• test/browser/msw-api/setup-worker/start/error.test.ts
• test/browser/graphql-api/custom-predicate.test.ts
• test/browser/msw-api/setup-worker/life-cycle-events/removeAllListeners.test.ts
• test/node/msw-api/setup-server/life-cycle-events/on.node.test.ts
• test/browser/msw-api/setup-worker/resetHandlers.test.ts
• test/typings/graphql-typed-document-string.test-d.ts
• test/browser/msw-api/setup-worker/stop/quiet.test.ts
• test/browser/msw-api/setup-worker/start/quiet.test.ts
• src/core/utils/internal/parseGraphQLRequest.test.ts
• src/core/utils/executeHandlers.ts
• test/support/ws-test-utils.ts
• src/node/setup-server-common.ts
• src/core/experimental/frames/http-frame.ts
• src/core/experimental/setup-api.ts
• test/typings/regressions/response-body-type.test-d.ts
• src/core/handlers/HttpHandler.test.ts
• test/browser/msw-api/setup-worker/life-cycle-events/removeListener.test.ts
• src/core/utils/internal/pipeEvents.ts
• test/browser/rest-api/request/matching/custom-predicate.test.ts
• test/node/graphql-api/batched-queries.apollo.test.ts
• src/browser/sources/service-worker-source.ts
• src/core/experimental/frames/http-frame.test.ts
• test/browser/msw-api/setup-worker/fallback-mode/fallback-mode.test.ts
• test/browser/sse-api/sse.retry.test.ts
• test/browser/msw-api/req/passthrough.test.ts
• test/typings/http-custom-predicate.test-d.ts
• test/browser/msw-api/setup-worker/start/find-worker.test.ts
• test/support/utils.ts
• src/node/setup-server.ts
• src/core/utils/handleRequest.test.ts
• src/core/experimental/index.ts
• src/core/graphql.ts
• src/core/ws/WebSocketClientManager.test.ts
• test/browser/sse-api/sse.client.send.multiline.test.ts
• test/browser/sse-api/sse.client.send.extraneous.test.ts
• src/core/ws/WebSocketClientManager.ts
• test/typings/custom-handler.test-d.ts
• test/typings/ws.test-d.ts
• src/core/handlers/HttpHandler.ts
• test/typings/regressions/request-handler-type.test-d.ts
• src/core/handlers/GraphQLHandler.test.ts
• test/typings/custom-resolver.test-d.ts
• test/browser/playwright.extend.ts
• test/browser/sse-api/sse.client.send.test.ts
• test/browser/sse-api/sse.with-credentials.test.ts
• src/core/handlers/RequestHandler.ts
• test/browser/msw-api/unregister.test.ts
• test/typings/define-network.test-d.ts
• test/browser/msw-api/setup-worker/scenarios/iframe/iframe.test.ts
• test/browser/sse-api/sse.quiet.test.ts
• src/browser/setup-worker.ts

🚧 Files skipped from review as they are similar to previous changes (3)

• src/core/experimental/frames/websocket-frame.test.ts
• src/core/ws.ts
• src/core/handlers/GraphQLHandler.ts

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📝 Walkthrough

Walkthrough

This PR converts numerous imports and exports throughout the codebase from runtime imports to TypeScript type-only imports, and enables the verbatimModuleSyntax compiler option to preserve the declared import syntax. This systematically separates type-only symbols from runtime values across core, browser, and Node modules.

Changes

Cohort / File(s)	Summary
Core Experimental Framework src/core/experimental/index.ts, src/core/experimental/define-network.ts, src/core/experimental/setup-api.ts, src/core/experimental/sources/interceptor-source.ts	Converted imports for DefineNetworkOptions, AnyHandler, HandlersController, LifeCycleEventEmitter, Interceptor, and RequestController to type-only imports where these symbols are only used for typing.
Core Experimental Frames src/core/experimental/frames/http-frame.ts, src/core/experimental/frames/http-frame.test.ts, src/core/experimental/frames/websocket-frame.ts, src/core/experimental/frames/websocket-frame.test.ts, src/core/experimental/on-unhandled-frame.test.ts	Changed imports for NetworkFrameResolutionContext, HandlersController, AnyHandler, UnhandledFrameHandle, HttpNetworkFrameEventMap, WebSocketNetworkFrameEventMap, and UnhandledFrameCallback to type-only imports in frame implementations and tests.
Core HTTP & GraphQL Handlers src/core/handlers/HttpHandler.ts, src/core/handlers/HttpHandler.test.ts, src/core/handlers/GraphQLHandler.ts, src/core/handlers/GraphQLHandler.test.ts, src/core/handlers/RequestHandler.ts	Converted type-related imports like ResponseResolver, RequestHandlerOptions, RequestHandlerDefaultInfo, Match, Path, DefaultBodyType, HttpResponseResolver, GraphQLRequestBody, and GraphQLResolverExtras to type-only imports.
Core Public APIs src/core/graphql.ts, src/core/http.ts, src/core/ws.ts	Changed exports and imports for ResponseResolver, RequestHandlerOptions, GraphQLVariables, GraphQLOperationType, HttpRequestResolverExtras, and WebSocketData to use type-only syntax.
Core Utilities src/core/utils/cookieStore.ts, src/core/utils/executeHandlers.ts, src/core/utils/handleRequest.ts, src/core/utils/handleRequest.test.ts, src/core/utils/internal/parseGraphQLRequest.test.ts, src/core/utils/internal/parseMultipartData.ts, src/core/utils/internal/pipeEvents.ts, src/core/utils/internal/requestHandlerUtils.ts, src/core/utils/request/onUnhandledRequest.test.ts	Converted imports for SerializedCookie, RequestHandler, RequestHandlerExecutionResult, Emitter, LifeCycleEventsMap, ParsedGraphQLRequest, DefaultRequestMultipartBody, EventMap, and UnhandledRequestCallback to type-only imports.
Browser Module src/browser/glossary.ts, src/browser/setup-worker.ts, src/browser/sources/service-worker-source.ts, src/browser/utils/deserializeRequest.ts	Changed AnyHandler, Emitter, WorkerChannelEventMap, FindWorker imports to type-only; removed an unused type-only import from deserializeRequest.ts.
Node Module src/node/async-handlers-controller.ts, src/node/setup-server-common.ts, src/node/setup-server.ts	Converted Interceptor, AnyHandler, HandlersController, HandlersControllerState, NetworkApi imports to type-only where appropriate.
WebSocket Support src/core/ws/WebSocketClientManager.ts, src/core/ws/WebSocketClientManager.test.ts, src/core/ws/WebSocketIndexedDBClientStore.ts, src/core/ws/WebSocketMemoryClientStore.ts, src/core/ws/handleWebSocketEvent.ts	Changed imports for WebSocketClientStore, WebSocketClientConnectionProtocol, SerializedWebSocketClient, RequestHandler, WebSocketHandler, and UnhandledRequestStrategy to type-only imports.
Browser Integration Tests test/browser/graphql-api/custom-predicate.test.ts, test/browser/graphql-api/response-patching.test.ts, test/browser/msw-api/context/delay.mocks.ts, test/browser/msw-api/req/passthrough.test.ts, test/browser/msw-api/setup-worker/.../*.test.ts, test/browser/rest-api/.../*.test.ts, test/browser/sse-api/.../*.test.ts, test/browser/playwright.extend.ts	Systematically converted MSW API imports (SetupWorkerApi, http, graphql, HttpResponse, LifeCycleEventsMap, ServerSentEventMessage, Page, Frame, etc.) to type-only imports across 30+ test files.
Node Integration Tests test/node/graphql-api/.../*.test.ts, test/node/msw-api/setup-server/.../*.test.ts, test/node/rest-api/.../*.test.ts, test/node/third-party/axios-error-response.test.ts	Changed MSW and third-party type imports (SetupServerApi, SetupServer, RequestHandler, GraphQLVariables, AxiosError) to type-only imports across 8+ test files.
Type Definition Tests test/typings/custom-handler.test-d.ts, test/typings/custom-resolver.test-d.ts, test/typings/define-network.test-d.ts, test/typings/graphql-typed-document-node.test-d.ts, test/typings/graphql-typed-document-string.test-d.ts, test/typings/http-custom-predicate.test-d.ts, test/typings/regressions/.../*.test-d.ts, test/typings/ws.test-d.ts	Converted type-related imports in typing tests (HttpRequestHandler, GraphQLRequestHandler, HttpResponseResolver, TypedDocumentNode, DocumentTypeDecoration, Path, DefaultBodyType, WebSocketData, WebSocketLink, etc.) to type-only imports.
Test Support test/support/WebSocketServer.ts, test/support/environments/vitest-environment-node-websocket.ts, test/support/graphql.ts, test/support/utils.ts, test/support/ws-test-utils.ts	Changed imports for FastifyInstance, Environment, DocumentTypeDecoration, TypedDocumentNode, ClientRequest, IncomingMessage, WebSocketData, WebSocketTransport, and WebSocketConnectionData to type-only imports.
TypeScript Configuration tsconfig.base.json	Added compilerOptions.verbatimModuleSyntax: true to enforce preservation of declared ESM/CJS import/export forms during TypeScript compilation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• mswjs/msw#2650: Adds the DefineNetworkOptions symbol to the experimental index, directly preceding this PR's conversion of that export to type-only.

Poem

🐰 A hop and skip through imports so fine,
Types now float, at compile time!
Runtime slims with syntax true,
Bundles bundle, just for you! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix: enabling and using verbatimModuleSyntax consistently to ensure type exports are properly handled.
Description check	✅ Passed	The description clearly explains the problem (runtime SyntaxError from type-only export), the fix, and context about broader TypeScript configuration changes.

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[kettanaito]

Thanks for opening this, @christoph-fricke. I've discovered a bigger issue: we weren't using verbatimModuleSyntax at all so there was no restriction to export types properly from the public entrypoints.

I've fixed that and updated everything we export/import publicly and internally.

[christoph-fricke]

@kettanaito Awesome! When I tried to verbatimModuleSyntax it caused weird, seemingly unrelated runtime errors in CI. I enabled it in tsconfig.base.json as well... Weird.

But I am glad it works now! Installed a local built into mswjs/playwright#48 and the tests run without crashing. Looks good to go from my POV.

[kettanaito]

Released: v2.13.4 🎉

This has been released in v2.13.4.

• 📄 Release notes
• 📦 View on npm

Get these changes by running the following command:

npm i msw@latest

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