Configurable max diff size

[norla]

Description of the Change

Fixes #4767

Mocha truncates large diffs before displaying a readable unified/inline comparison.
This means that they are not displayed at all for larger strings in many cases, which causes confusion.
This PR makes the limit for when diffs should be truncated configurable (via "--reporter-option maxDiffSize=number"), so that projects that have large diffs can still get the outout they expect.

The default limit for generating diffs is also increased from 2048 to 8192 character, so that fewer people will run into this situation to begin with.

Also fixes bug causing the message about text being truncated to disappear.

Alternate Designs

Why should this be in core?

Fix for things already in core :)

Benefits

Configurable limit ensures that each project can configure the cropping of strings before shoving diff according to their own needs.

Possible Drawbacks

One more config flag to consider/document etc.

Applicable issues

#4767

[nopeless]

Personally never ran into this issue, but I can see myself running into this in the future 👍

[sz-piotr]

I have run into this multiple times, would really appreciate this getting more attention.

[juergba]

@norla thank you for this PR.

I'm not convinced of appending an additional option for this parameter.
Nevertheless we already have a reporter specific option reporter-option which could be enhanced for this case. We already use it for writing test results to a file.

Usage:

• CLI: --reporter-option diffSize=4048
• config files: 'reporter-option': ['diffSize=4048']

[norla]

@juergba makes sense, didn't know about reporter options until now :)
The PR is updated accordingly, I named the option "maxDiffSize".

Another thing I just thought of:
The default value 2048 seems very conservative, maybe it can be increased to something like 8192 or 16384 instead?
I think that would prevent a lot of people from having to fiddle with "maxDiffSize" in the first place.

[juergba]

@norla thank you, I will have a look this week.

[coveralls]

Coverage increased (+0.01%) to 94.444% when pulling 40bac95 on norla:configurable-max-diff-size into 509938d on mochajs:master.

[drGeoBN]

LGTM

[juergba]

@norla please don't push commit by commit, our resources on the CI servers e.g. netlify are limited.
Test locally, then push occasionally.

[juergba]

@norla thank you so far. I will do some testing tomorrow.
Evtl. I can find a way to simplify this Number.isNaN check a little bit.

You could update this issue description (reporter-option / maxDiffSize, 2048=> 8192, fix message) and squash your commits.
Then lets see what the test coverage is telling.

Edit: ... and rebase to master.

[norla]

Sure! I will try to do this (and the other stuff) later this weekend. Den lör 12 feb. 2022 kl 09:59 skrev Juerg B. ***@***.***>:

…

***@***.**** commented on this pull request. ------------------------------ In test/reporters/base.spec.js <#4799 (comment)>: > }); it("should truncate overly long 'expected' ", function () { + var actual = 'a foo unified diff'; These tests don't cover the usage of reporter-option maxDiffSize=0. There are similar tests for the spec and json reporters, indeed terrible tests. Could you have a look and try to add one test, please? — Reply to this email directly, view it on GitHub <#4799 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAYTYDP7DSBTHZNU7XEKJRLU2YON5ANCNFSM5KDG2BAQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[norla]

I've fixed your comments. A bit unsure about the extra test but hopefully it should be enough. Let me know otherwise.
Still need to rebase and squash, though. Tomorrow :)

[juergba]

@norla thank you very much! Please rebase/squash and mention the --reporter-option maxDiffsize=number information in your issue description. I'm planning to release this fix next weekend.