Adds an overwrite for the TS module system when transpiling our TS code

CHANGELOG.md

@@ -3,6 +3,10 @@ developers, so please limit technical // terminology to in here.
 
 // ### Master
 
+### 2.1.5
+
+* The TS compiler will force a module type of commonjs when transpiling the Dangerfile - [@orta][]
+
 ### 2.1.4
 
 * Adds a CLI option for a unique Danger ID per run to `danger` and `danger process`,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "danger",
-  "version": "2.1.4",
+  "version": "2.1.5",
   "description": "Unit tests for Team Culture",
   "main": "distribution/danger.js",
   "typings": "distribution/danger.d.ts",

source/runner/runners/utils/_tests/_transpiler.test.ts

@@ -0,0 +1,22 @@
+jest.mock("fs", () => ({
+  readFileSync: jest.fn(),
+}))
+
+import { typescriptify } from "../transpiler"
+import * as fs from "fs"
+
+describe("typescriptify", () => {
+  it("removes the module option in a tsconfig ", () => {
+    const dangerfile = `import {a} from 'lodash'; a()`
+    const fakeTSConfig = {
+      compilerOptions: {
+        target: "es5",
+        module: "es2015",
+      },
+    }
+    const fsMock = fs.readFileSync as any
+    fsMock.mockImplementationOnce(() => JSON.stringify(fakeTSConfig))
+
+    expect(typescriptify(dangerfile)).not.toContain("import")
+  })
+})

source/runner/runners/utils/transpiler.ts

@@ -34,10 +34,31 @@ try {
 export const typescriptify = (content: string): string => {
   const ts = require("typescript") // tslint:disable-line
   const compilerOptions = JSON.parse(fs.readFileSync("tsconfig.json", "utf8"))
-  let result = ts.transpileModule(content, compilerOptions)
+  let result = ts.transpileModule(content, sanitizeTSConfig(compilerOptions))
   return result.outputText
 }
 
+const sanitizeTSConfig = (config: any) => {
+  if (!config.compilerOptions) {
+    return config
+  }
+
+  const safeConfig = config
+
+  // It can make sense to ship TS code with modules
+  // for `import`/`export` syntax, but as we're running
+  // the transpiled code on vanilla node - it'll need to
+  // be used with plain old commonjs
+  //
+  // @see https://github.com/apollographql/react-apollo/pull/1402#issuecomment-351810274
+  //
+  if (safeConfig.compilerOptions.module) {
+    safeConfig.compilerOptions.module = "commonjs"
+  }
+
+  return safeConfig
+}
+
 export const babelify = (content: string, filename: string, extraPlugins: string[]): string => {
   const babel = require("babel-core") // tslint:disable-line
   if (!babel.transform) {