fix: capture non error type in json reporter (#856)

__tests__/reporters/__snapshots__/json.test.ts.snap

@@ -209,7 +209,7 @@ exports[`json reporter writes each step as NDJSON to the FD 1`] = `
 {"type":"step/filmstrips","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1"},"step":{"name":"s1","index":1},"root_fields":{"browser":{"relative_trace":{"start":{"us":392583998697}}},"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"index":0},"blob":"dummy","blob_mime":"image/jpeg","package_version":"0.0.1"}
 {"type":"step/end","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1"},"step":{"name":"s1","index":1,"status":"succeeded","duration":{"us":10000000}},"root_fields":{"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"source":"function noop() { }","url":"dummy","status":"succeeded"},"url":"dummy","package_version":"0.0.1"}
 {"type":"journey/network_info","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1"},"root_fields":{"user_agent":{},"http":{"request":{}},"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"browser":{},"is_navigation_request":true},"package_version":"0.0.1"}
-{"type":"journey/browserconsole","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1"},"step":{"name":"step-name","index":0},"root_fields":{"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"text":"Boom","type":"error"},"error":{"name":"Error","message":"boom","stack":""},"package_version":"0.0.1"}
+{"type":"journey/browserconsole","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1"},"step":{"name":"step-name","index":0},"root_fields":{"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"text":"Boom","type":"error"},"error":{"name":"Error","message":"boom","stack":"at /foo/bar.js:1:1"},"package_version":"0.0.1"}
 {"type":"journey/end","@timestamp":1600300800000000,"journey":{"name":"j1","id":"j1","status":"succeeded"},"root_fields":{"os":{"platform":"darwin"},"package":{"name":"@elastic/synthetics","version":"0.0.1"}},"payload":{"start":0,"end":11,"status":"succeeded"},"package_version":"0.0.1"}
 "
 `;

__tests__/reporters/json.test.ts

@@ -103,7 +103,7 @@ describe('json reporter', () => {
 
   it('writes each step as NDJSON to the FD', async () => {
     const error = new Error('boom');
-    error.stack = '';
+    error.stack = 'at /foo/bar.js:1:1';
     reporter.onJourneyRegister(j1);
     reporter.onJourneyStart(j1, {
       timestamp,
@@ -229,6 +229,22 @@ describe('json reporter', () => {
     expect(journeyEnd.error.stack).toContain(`Error: myError`);
   });
 
+  it('captures non-error types', async () => {
+    reporter.onJourneyEnd(j1, {
+      timestamp,
+      start: 0,
+      end: 1,
+      status: 'failed',
+      error: 'boom' as any,
+      options: {},
+    });
+
+    const journeyEnd = (await readAndCloseStreamJson()).find(
+      json => json.type == 'journey/end'
+    );
+    expect(journeyEnd.error.message).toContain(`thrown: 'boom'`);
+  });
+
   it('writes full journey info if present', async () => {
     const journeyOpts = { name: 'name', id: 'id', tags: ['tag1', 'tag2'] };
 

src/reporters/json.ts

@@ -52,6 +52,7 @@ import {
   JourneyEndResult,
   PageMetrics,
 } from '../common_types';
+import { inspect } from 'util';
 
 /* eslint-disable @typescript-eslint/no-var-requires */
 const { version, name } = require('../../package.json');
@@ -198,6 +199,11 @@ function formatJSONError(error: Error | any, type: OutputType) {
     return;
   }
 
+  // Early exit for non Error objects
+  if (!(error instanceof Error) || !error.stack) {
+    return { message: `thrown: ${inspect(error)}` };
+  }
+
   /**
    * Do not process browser errors - console.error and unhandled exceptions
    */