exception message in json formatter

src/formatter/helpers/error_helpers.js

@@ -1,3 +1,4 @@
+import _ from 'lodash'
 import { format } from 'assertion-error-formatter'
 
 export function formatError(error, colorFns) {
@@ -10,3 +11,15 @@ export function formatError(error, colorFns) {
     }
   })
 }
+
+export function stringifyException(exception) {
+  if (_.isString(exception)) return exception
+
+  let { message, stack } = exception
+  if (_.includes(stack, message)) return stack
+  if (message && stack) return message + '\n' + stack
+  if (message) return message
+  if (stack) return stack
+
+  return JSON.stringify(exception)
+}

src/formatter/helpers/error_helpers_spec.js

@@ -0,0 +1,41 @@
+import { stringifyException } from './error_helpers'
+
+describe('ErrorHelpers', function() {
+  describe('stringifyException', function() {
+    it('return string on string exception', function() {
+      let error_message = stringifyException('error')
+      expect(error_message).to.equal('error')
+    })
+
+    it('return message', function() {
+      let error_message = stringifyException({ message: 'error' })
+      expect(error_message).to.equal('error')
+    })
+
+    it('return stack', function() {
+      let error_message = stringifyException({ stack: 'stack' })
+      expect(error_message).to.equal('stack')
+    })
+
+    it('return message and stack', function() {
+      let error_message = stringifyException({
+        message: 'error',
+        stack: 'stack'
+      })
+      expect(error_message).to.equal('error\nstack')
+    })
+
+    it('do not repeat message', function() {
+      let error_message = stringifyException({
+        message: 'error',
+        stack: 'error\nstack'
+      })
+      expect(error_message).to.equal('error\nstack')
+    })
+
+    it('stringify an object', function() {
+      let error_message = stringifyException({ prop: 'error' })
+      expect(error_message).to.equal('{"prop":"error"}')
+    })
+  })
+})

src/formatter/helpers/index.js

@@ -3,7 +3,7 @@ import * as PickleParser from './pickle_parser'
 
 export { default as EventDataCollector } from './event_data_collector'
 export { default as KeywordType, getStepKeywordType } from './keyword_type'
-export { formatError } from './error_helpers'
+export { formatError, stringifyException } from './error_helpers'
 export { formatIssue, isIssue } from './issue_helpers'
 export { formatLocation } from './location_helpers'
 export { formatSummary } from './summary_helpers'

src/formatter/json_formatter.js

@@ -1,7 +1,12 @@
 import _ from 'lodash'
 import Formatter from './'
 import Status from '../status'
-import { formatLocation, GherkinDocumentParser, PickleParser } from './helpers'
+import {
+  formatLocation,
+  GherkinDocumentParser,
+  PickleParser,
+  stringifyException
+} from './helpers'
 import { buildStepArgumentIterator } from '../step_arguments'
 
 const {
@@ -156,7 +161,7 @@ export default class JsonFormatter extends Formatter {
         data.result.duration = testStep.result.duration
       }
       if (status === Status.FAILED && exception) {
-        data.result.error_message = exception.stack || exception
+        data.result.error_message = stringifyException(exception)
       }
     }
     if (_.size(testStep.attachments) > 0) {