"Invalid string length" and memory issues

[adaphi]

Hello,

We've been having issues where using mochawesome as a reporter causes the node process to run out of memory. We have a fairly large number of tests to run (~800), but when run with no reporter they work just fine.

After vastly reducing the number of tests (to ~40) I managed to get the following related error:

Problem with mochawesome: RangeError: Invalid string length
    at join (native)
    at Object.stringify (native)
    at stringify (/usr/lib/node_modules/mochawesome/node_modules/json-stringify-safe/stringify.js:5:15)
    at Runner.<anonymous> (/usr/lib/node_modules/mochawesome/lib/mochawesome.js:116:20)
    at emitNone (events.js:72:20)
    at Runner.emit (events.js:166:7)
    at /usr/lib/node_modules/mocha/lib/runner.js:791:12
    at /usr/lib/node_modules/mocha/lib/runner.js:644:9
    at next (/usr/lib/node_modules/mocha/lib/runner.js:284:14)
    at Immediate._onImmediate (/usr/lib/node_modules/mocha/lib/runner.js:320:5)
    at processImmediate [as _immediateCallback] (timers.js:383:17)

Reducing it further (to 12!) then works fine.

The problem seems to be that each hook in the allHooks part of the object being passed to stringify (lib/mochawesome.js:116) contains two circular references - stringify does detect some of this but it results in a huge amount of duplicated stuff in the output. This vastly multiplies the impact of having many hooks alongside tests with a large body of content. When running with a large number of tests, the process runs out of memory before it is able to produce the error.

Attached is a file that will reproduce the problem, at least on my machine. Since it's a memory issue YMMV! It's a bit contrived but the idea is simply to show how a large number of hooks, tests, or a large test code body all contribute. Making the code body smaller doesn't entirely solve the issue, it just prevents it from happening until the test count is higher.

Versions:
node v4.3.2
mocha 2.4.5
mochawesome 1.3.1
Running via command line.

Is this something fixable?

mochawesomeMemTest.zip

[adamgruber]

@adaphi Thanks for the detailed write up and example code. Very much appreciated. I'll take a look into this and see what I can do.

[adamgruber]

Published 1.3.2 to fix this.

[adaphi]

Verified that this resolves the issue. Thanks @adamgruber for the quick fix!