add option to handle a given set of mime types as blob

Author: Lucas Treffenstädt

src/fetcher.ts

@@ -13,6 +13,8 @@ import {
   Request,
   _TypedFetch,
   TypedFetch,
+  ContentTypeDiscriminator,
+  BlobTypeSelector,
 } from './types'
 
 const sendBody = (method: Method) =>
@@ -134,13 +136,18 @@ function getFetchParams(request: Request) {
   return { url, init }
 }
 
-async function getResponseData(response: Response) {
+async function getResponseData(response: Response, isBlob: BlobTypeSelector) {
   const contentType = response.headers.get('content-type')
   if (response.status === 204 /* no content */) {
     return undefined
   }
-  if (contentType && contentType.indexOf('application/json') !== -1) {
-    return response.json()
+  if (contentType) {
+    if (isBlob(contentType)) {
+      return response.blob()
+    }
+    if (contentType.includes('application/json')) {
+      return response.json()
+    }
   }
   const text = await response.text()
   try {
@@ -150,25 +157,32 @@ async function getResponseData(response: Response) {
   }
 }
 
-async function fetchJson(url: string, init: RequestInit): Promise<ApiResponse> {
-  const response = await fetch(url, init)
-
-  const data = await getResponseData(response)
+function getFetchResponse(blobTypeSelector: BlobTypeSelector) {
+  async function fetchResponse(
+    url: string,
+    init: RequestInit,
+  ): Promise<ApiResponse> {
+    const response = await fetch(url, init)
+
+    const data = await getResponseData(response, blobTypeSelector)
+
+    const result = {
+      headers: response.headers,
+      url: response.url,
+      ok: response.ok,
+      status: response.status,
+      statusText: response.statusText,
+      data,
+    }
 
-  const result = {
-    headers: response.headers,
-    url: response.url,
-    ok: response.ok,
-    status: response.status,
-    statusText: response.statusText,
-    data,
-  }
+    if (result.ok) {
+      return result
+    }
 
-  if (result.ok) {
-    return result
+    throw new ApiError(result)
   }
 
-  throw new ApiError(result)
+  return fetchResponse
 }
 
 function wrapMiddlewares(middlewares: Middleware[], fetch: Fetch): Fetch {
@@ -227,24 +241,47 @@ function createFetch<OP>(fetch: _TypedFetch<OP>): TypedFetch<OP> {
   return fun
 }
 
+function getBlobTypeSelector(discriminator?: ContentTypeDiscriminator) {
+  if (!discriminator) {
+    return () => false
+  }
+  if (typeof discriminator === 'function') {
+    return discriminator
+  }
+  let arrayDiscriminator = discriminator
+  if (!Array.isArray(discriminator)) {
+    arrayDiscriminator = [discriminator]
+  }
+  const arrayOfRegExp = (arrayDiscriminator as Array<string | RegExp>).map(
+    (expr) => (expr instanceof RegExp ? expr : new RegExp(`^.*${expr}.*$`)),
+  )
+  return (contentType: string) =>
+    Boolean(arrayOfRegExp.find((expr) => expr.test(contentType)))
+}
+
 function fetcher<Paths>() {
   let baseUrl = ''
   let defaultInit: RequestInit = {}
   const middlewares: Middleware[] = []
-  const fetch = wrapMiddlewares(middlewares, fetchJson)
+  let blobTypeSelector: BlobTypeSelector = () => false
 
   return {
     configure: (config: FetchConfig) => {
       baseUrl = config.baseUrl || ''
       defaultInit = config.init || {}
       middlewares.splice(0)
       middlewares.push(...(config.use || []))
+      blobTypeSelector = getBlobTypeSelector(config.asBlob)
     },
     use: (mw: Middleware) => middlewares.push(mw),
     path: <P extends keyof Paths>(path: P) => ({
       method: <M extends keyof Paths[P]>(method: M) => ({
-        create: ((queryParams?: Record<string, true | 1>) =>
-          createFetch((payload, init) =>
+        create: ((queryParams?: Record<string, true | 1>) => {
+          const fetch = wrapMiddlewares(
+            middlewares,
+            getFetchResponse(blobTypeSelector),
+          )
+          return createFetch((payload, init) =>
             fetchUrl({
               baseUrl: baseUrl || '',
               path: path as string,
@@ -254,7 +291,8 @@ function fetcher<Paths>() {
               init: mergeRequestInit(defaultInit, init),
               fetch,
             }),
-          )) as CreateFetch<M, Paths[P][M]>,
+          )
+        }) as CreateFetch<M, Paths[P][M]>,
       }),
     }),
   }

src/types.ts

@@ -127,10 +127,19 @@ export type Middleware = (
   next: Fetch,
 ) => Promise<ApiResponse>
 
+export type BlobTypeSelector = (contentType: string) => boolean
+
+export type ContentTypeDiscriminator =
+  | string
+  | RegExp
+  | Array<string | RegExp>
+  | BlobTypeSelector
+
 export type FetchConfig = {
   baseUrl?: string
   init?: RequestInit
   use?: Middleware[]
+  asBlob?: ContentTypeDiscriminator
 }
 
 export type Request = {

test/fetch.test.ts

@@ -10,16 +10,17 @@ afterAll(() => server.close())
 
 describe('fetch', () => {
   const fetcher = Fetcher.for<paths>()
+  const defaultFetcherConfig = {
+    baseUrl: 'https://api.backend.dev',
+    init: {
+      headers: {
+        Authorization: 'Bearer token',
+      },
+    },
+  }
 
   beforeEach(() => {
-    fetcher.configure({
-      baseUrl: 'https://api.backend.dev',
-      init: {
-        headers: {
-          Authorization: 'Bearer token',
-        },
-      },
-    })
+    fetcher.configure(defaultFetcherConfig)
   })
 
   const expectedHeaders = {
@@ -270,4 +271,117 @@ describe('fetch', () => {
     expect(captured.url).toEqual('https://api.backend.dev/bodyquery/1?scalar=a')
     expect(captured.body).toEqual('{"list":["b","c"]}')
   })
+
+  it('GET /blob (with single content type)', async () => {
+    fetcher.configure({ ...defaultFetcherConfig, asBlob: 'application/pdf' })
+
+    const fun = fetcher.path('/blob').method('post').create()
+
+    const { data } = await fun(
+      { value: 'test' },
+      {
+        headers: {
+          Accept: 'application/pdf',
+        },
+      },
+    )
+
+    expect(data).toBeInstanceOf(Blob)
+  })
+
+  it('GET /blob (with single regex)', async () => {
+    fetcher.configure({
+      ...defaultFetcherConfig,
+      asBlob: /^application\/(?!json)/,
+    })
+
+    const fun = fetcher.path('/blob').method('post').create()
+
+    for (const mimeType of ['application/octet-stream', 'application/zip']) {
+      const { data } = await fun(
+        { value: 'test' },
+        {
+          headers: {
+            Accept: mimeType,
+          },
+        },
+      )
+
+      expect(data).toBeInstanceOf(Blob)
+    }
+
+    for (const mimeType of ['text/plain', 'text/plain;charset=utf-8']) {
+      const { data } = await fun(
+        { value: 'test' },
+        {
+          headers: {
+            Accept: mimeType,
+          },
+        },
+      )
+
+      expect(typeof data).toBe('string')
+    }
+
+    for (const mimeType of ['text/plain', 'application/json;charset=utf-8']) {
+      const { data } = await fun(
+        { value: JSON.stringify({ value: 'test' }) },
+        {
+          headers: {
+            Accept: mimeType,
+          },
+        },
+      )
+
+      expect(data).toEqual({ value: 'test' })
+    }
+  })
+
+  it('GET /blob (with list of mime types)', async () => {
+    fetcher.configure({
+      ...defaultFetcherConfig,
+      asBlob: ['application/octet-stream', 'audio/vorbis'],
+    })
+
+    const fun = fetcher.path('/blob').method('post').create()
+
+    for (const mimeType of ['application/octet-stream', 'audio/vorbis']) {
+      const { data } = await fun(
+        { value: 'test' },
+        {
+          headers: {
+            Accept: mimeType,
+          },
+        },
+      )
+
+      expect(data).toBeInstanceOf(Blob)
+    }
+  })
+
+  it('GET /blob (with custom discriminator function', async () => {
+    fetcher.configure({
+      ...defaultFetcherConfig,
+      asBlob: (contentType) => contentType.startsWith('application'),
+    })
+
+    const fun = fetcher.path('/blob').method('post').create()
+
+    for (const mimeType of [
+      'application/octet-stream',
+      'application/zip',
+      'application/json',
+    ]) {
+      const { data } = await fun(
+        { value: 'test' },
+        {
+          headers: {
+            Accept: mimeType,
+          },
+        },
+      )
+
+      expect(data).toBeInstanceOf(Blob)
+    }
+  })
 })

test/mocks/handlers.ts

@@ -36,6 +36,13 @@ function getResult(
   )
 }
 
+function getBlob(req: RestRequest, res: ResponseComposition, ctx: RestContext) {
+  return res(
+    ctx.body(new Blob([(req.body as Record<string, string>)['value']])),
+    ctx.set('Content-Type', req.headers.get('accept') ?? 'application/pdf'),
+  )
+}
+
 const HOST = 'https://api.backend.dev'
 
 const methods = {
@@ -49,6 +56,10 @@ const methods = {
   withBodyAndQuery: ['post', 'put', 'patch', 'delete'].map((method) => {
     return (rest as any)[method](`${HOST}/bodyquery/:id`, getResult)
   }),
+  withBlob: [
+    rest.get(`${HOST}/blob`, getBlob),
+    rest.post(`${HOST}/blob`, getBlob),
+  ],
   withError: [
     rest.get(`${HOST}/error/:status`, (req, res, ctx) => {
       const status = Number(req.params.status)
@@ -79,6 +90,7 @@ const methods = {
 export const handlers = [
   ...methods.withQuery,
   ...methods.withBody,
+  ...methods.withBlob,
   ...methods.withBodyArray,
   ...methods.withBodyAndQuery,
   ...methods.withError,

test/paths.ts

@@ -39,6 +39,17 @@ type BodyAndQuery = {
   responses: { 201: { schema: Data } }
 }
 
+type BodyBlob = {
+  parameters: {
+    body: { payload: { value: string } }
+  }
+  responses: {
+    200: {
+      schema: unknown
+    }
+  }
+}
+
 export type paths = {
   '/query/{a}/{b}': {
     get: Query
@@ -61,6 +72,9 @@ export type paths = {
     patch: BodyAndQuery
     delete: BodyAndQuery
   }
+  '/blob': {
+    post: BodyBlob
+  }
   '/nocontent': {
     post: {
       parameters: {}