Block uncomment throws exception near bottom of file

[njx]

1. Open the Getting Started project
2. Open and close an inline editor
3. Go to the CSS file and select the last 2 lines within the last selector
4. Block comment
5. Block uncomment

Result: exception thrown in CodeMirror (although things seem to work fine afterward)

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Original description:

Failures:

• EditorCommandHandlers Block comment/uncomment should block uncomment, cursor in whitespace within block comment.
• EditorCommandHandlers Block comment/uncomment should block uncomment, selection in whitespace within block comment.

Both seem to be the same issue: TypeError: Cannot call method 'chunkSize' of undefined.

This only happens if certain other test suites are run before this one (so you have to run all the test suites, and the tests have to load in a certain order).

[njx]

To @peterflynn

[TomMalbran]

I think it might be problem with #2335

[peterflynn]

I ran unit tests (the full "All") manually on the Jenkins machine and they all pass. Also ran this suite locally on my machine and it passes, and NJ confirms same on his machine.

I'm not seeing any evidence linking this to the tokenization race condition, other than it being not 100% reproducible. In #2335, the symptom was the command getting stale tokens back from CM and thinking some stuff was commented out when it wasn't (or vice versa). Here the symptom is CM crashing in updateDisplay() after we've made some edits... which often implies we passed it undefined or NaN as a line number at some point.

[peterflynn]

Looking like a CM bug -- and it only occurs if CM has ever seen hidden lines (e.g. an inline editor before), which means whether or not this repros depends on the (nondeterministic) order that other test suites got run in. Will file an issue and disable the two tests for now.

[peterflynn]

Filed codemirror/codemirror5#1255. Put up a pull request for disabling the tests, so reducing this to Low & adding Tracking label.

[peterflynn]

Adding new info: there is a user-visible bug here too, but it's a little tricky to hit and not readily apparent unless you have Dev Tools open. Bumping up to Medium, though...

The CM bug is now fixed, so this will be fixed with our next merge from upstream.

[njx]

FBNC to @peterflynn

[peterflynn]

Confirmed fixed