adds helpful error message when files is overridden or empty

src/util/__tests__/config-file.js

@@ -19,6 +19,15 @@ const NoNameConfigFile = {
   contributorsPerLine: 6,
   contributors: [],
 }
+const NoFilesConfigFile = {
+  projectOwner: 'jfmengels',
+  projectName: 'all-contributors-cli',
+  imageSize: 100,
+  commit: false,
+  contributorsPerLine: 6,
+  contributors: [],
+  files: [],
+}
 
 test('Reading an absent configuration file throws a helpful error', () => {
   expect(() => configFile.readConfig(absentFile)).toThrowError(
@@ -41,3 +50,11 @@ test('Should throw error and not allow editing config file if project name or ow
     configFile.writeConfig(incompleteConfigFilePath, NoNameConfigFile),
   ).toThrow(`Error! Project name is not set in ${incompleteConfigFilePath}`)
 })
+
+test(`throws if 'files' was overridden in .all-contributorsrc and is empty`, () => {
+  expect(() =>
+    configFile.writeConfig(incompleteConfigFilePath, NoFilesConfigFile),
+  ).toThrow(
+    `Error! Project files was overridden and is empty in ${incompleteConfigFilePath}`,
+  )
+})

src/util/config-file.js

@@ -24,6 +24,11 @@ function writeConfig(configPath, content) {
   if (!content.projectName) {
     throw new Error(`Error! Project name is not set in ${configPath}`)
   }
+  if (!content.files.length) {
+    throw new Error(
+      `Error! Project files was overridden and is empty in ${configPath}`,
+    )
+  }
   return pify(fs.writeFile)(configPath, `${JSON.stringify(content, null, 2)}\n`)
 }