fix: if the purge api call fails, include the api response body in th…

…e thrown error's message (#571)

.eslintrc.js

@@ -6,6 +6,7 @@ module.exports = {
   extends: '@netlify/eslint-config-node',
   rules: {
     'max-statements': 'off',
+    'max-lines': 'off',
   },
   overrides: [
     ...overrides,

src/lib/purge_cache.test.ts

@@ -58,9 +58,11 @@ test('Calls the purge API endpoint and returns `undefined` if the operation was
   expect(mockAPI.fulfilled).toBeTruthy()
 })
 
-test('Throws if the API response does not have a successful status code', async () => {
+test('Throws an error if the API response does not have a successful status code, using the response body as part of the error message', async () => {
   if (!hasFetchAPI) {
     console.warn('Skipping test requires the fetch API')
+
+    return
   }
 
   const mockSiteID = '123456789'
@@ -77,7 +79,7 @@ test('Throws if the API response does not have a successful status code', async
     },
     headers: { Authorization: `Bearer ${mockToken}` },
     method: 'post',
-    response: new Response(null, { status: 500 }),
+    response: new Response('site not found', { status: 404 }),
     url: `https://api.netlify.com/api/v1/purge`,
   })
   // eslint-disable-next-line unicorn/consistent-function-scoping
@@ -90,14 +92,54 @@ test('Throws if the API response does not have a successful status code', async
   try {
     await invokeLambda(myFunction)
 
-    throw new Error('Invocation should have failed')
+    expect.fail('Invocation should have failed')
   } catch (error) {
     expect((error as NodeJS.ErrnoException).message).toBe(
-      'Cache purge API call returned an unexpected status code: 500',
+      'Cache purge API call was unsuccessful.\nStatus: 404\nBody: site not found',
     )
   }
 })
 
+test('Throws if the API response does not have a successful status code, does not include the response body if it is not text', async () => {
+  if (!hasFetchAPI) {
+    console.warn('Skipping test requires the fetch API')
+
+    return
+  }
+
+  const mockSiteID = '123456789'
+  const mockToken = '1q2w3e4r5t6y7u8i9o0p'
+
+  process.env.NETLIFY_PURGE_API_TOKEN = mockToken
+  process.env.SITE_ID = mockSiteID
+
+  const mockAPI = new MockFetch().post({
+    body: (payload: string) => {
+      const data = JSON.parse(payload)
+
+      expect(data.site_id).toBe(mockSiteID)
+    },
+    headers: { Authorization: `Bearer ${mockToken}` },
+    method: 'post',
+    response: new Response(null, { status: 500 }),
+    url: `https://api.netlify.com/api/v1/purge`,
+  })
+  // eslint-disable-next-line unicorn/consistent-function-scoping
+  const myFunction = async () => {
+    await purgeCache()
+  }
+
+  globalThis.fetch = mockAPI.fetcher
+
+  try {
+    await invokeLambda(myFunction)
+
+    throw new Error('Invocation should have failed')
+  } catch (error) {
+    expect((error as NodeJS.ErrnoException).message).toBe('Cache purge API call was unsuccessful.\nStatus: 500')
+  }
+})
+
 test('Ignores purgeCache if in local dev with no token or site', async () => {
   if (!hasFetchAPI) {
     console.warn('Skipping test requires the fetch API')

src/lib/purge_cache.ts

@@ -38,6 +38,14 @@ export const purgeCache = async (options: PurgeCacheOptions = {}) => {
     )
   }
 
+  const { siteID } = options as PurgeCacheOptionsWithSiteID
+  const { siteSlug } = options as PurgeCacheOptionsWithSiteSlug
+  const { domain } = options as PurgeCacheOptionsWithDomain
+
+  if ((siteID && siteSlug) || (siteID && domain) || (siteSlug && domain)) {
+    throw new Error('Can only pass one of either "siteID", "siteSlug", or "domain"')
+  }
+
   const payload: PurgeAPIPayload = {
     cache_tags: options.tags,
     deploy_alias: options.deployAlias,
@@ -50,22 +58,20 @@ export const purgeCache = async (options: PurgeCacheOptions = {}) => {
     return
   }
 
-  if ('siteSlug' in options) {
-    payload.site_slug = options.siteSlug
-  } else if ('domain' in options) {
-    payload.domain = options.domain
+  if (siteSlug) {
+    payload.site_slug = siteSlug
+  } else if (domain) {
+    payload.domain = domain
   } else {
     // The `siteID` from `options` takes precedence over the one from the
     // environment.
-    const siteID = options.siteID || env.SITE_ID
+    payload.site_id = siteID || env.SITE_ID
 
-    if (!siteID) {
+    if (!payload.site_id) {
       throw new Error(
         'The Netlify site ID was not found in the execution environment. Please supply it manually using the `siteID` property.',
       )
     }
-
-    payload.site_id = siteID
   }
 
   if (!token) {
@@ -91,6 +97,13 @@ export const purgeCache = async (options: PurgeCacheOptions = {}) => {
   })
 
   if (!response.ok) {
-    throw new Error(`Cache purge API call returned an unexpected status code: ${response.status}`)
+    let text
+    try {
+      text = await response.text()
+    } catch {}
+    if (text) {
+      throw new Error(`Cache purge API call was unsuccessful.\nStatus: ${response.status}\nBody: ${text}`)
+    }
+    throw new Error(`Cache purge API call was unsuccessful.\nStatus: ${response.status}`)
   }
 }