Merge multiple accept headers, instead of having them conflicting

changelog.md

@@ -2,7 +2,10 @@
 
 ### Master
 
-- Fixed #348 invalid json response body error - felipesabino
+### 2.0.0-alpha.12
+
+- Fixed #348 invalid json response body error on generating a diff - felipesabino
+- Potential fix for ^ that works with Peril also - orta
 
 ### 2.0.0-alpha.11
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "danger",
-  "version": "2.0.0-alpha.11",
+  "version": "2.0.0-alpha.12",
   "description": "Unit tests for Team Culture",
   "main": "distribution/danger.js",
   "typings": "distribution/danger.d.ts",

source/platforms/github/GitHubAPI.ts

@@ -211,7 +211,7 @@ export class GitHubAPI {
     const prJSON = await this.getPullRequestInfo()
     const diffURL = prJSON["diff_url"]
     const res = await this.get(diffURL, {
-      accept: "application/vnd.github.v3.diff",
+      Accept: "application/vnd.github.v3.diff",
     })
 
     return res.ok ? res.text() : ""
@@ -287,13 +287,20 @@ export class GitHubAPI {
     const baseUrl = process.env["DANGER_GITHUB_API_BASE_URL"] || "https://api.github.com"
     const url = containsBase ? path : `${baseUrl}/${path}`
 
+    let customAccept = {}
+    if (headers.Accept && this.additionalHeaders.Accept) {
+      // We need to merge the accepts which are comma separated according to the HTML spec
+      // e.g. https://gist.github.com/LTe/5270348
+      customAccept = { Accept: `${this.additionalHeaders.Accept}, ${headers.Accept}` }
+    }
     return this.fetch(url, {
       method: method,
       body: body,
       headers: {
         "Content-Type": "application/json",
         ...headers,
         ...this.additionalHeaders,
+        ...customAccept,
       },
     })
   }

source/platforms/github/_tests/_github_api.test.ts

@@ -80,7 +80,7 @@ describe("API testing", () => {
       api: "https://github.com/artsy/emission/pull/327.diff",
       headers: {
         Authorization: "token ABCDE",
-        accept: "application/vnd.github.v3.diff",
+        Accept: "application/vnd.github.v3.diff",
         "Content-Type": "application/json",
       },
     })
@@ -110,6 +110,24 @@ describe("Peril", () => {
     })
   })
 
+  it("Merges two Accept headers", async () => {
+    api.additionalHeaders = { Accept: "application/vnd.github.machine-man-preview+json" }
+
+    const request = await api.get("user", {
+      Accept: "application/vnd.github.v3.diff",
+    })
+
+    expect(api.fetch).toHaveBeenCalledWith("https://api.github.com/user", {
+      body: {},
+      headers: {
+        Accept: "application/vnd.github.machine-man-preview+json, application/vnd.github.v3.diff",
+        Authorization: "token ABCDE",
+        "Content-Type": "application/json",
+      },
+      method: "GET",
+    })
+  })
+
   describe("Allows setting DANGER_GITHUB_APP env variable", () => {
     beforeEach(() => {
       process.env.DANGER_GITHUB_APP = "1"