CM6: Several conflict gutter markers placed on the same line

[HaudinFlorence]

When trying to run example6, the following issue has been observed in the merge editor: several conflict gutter markers are produced at the same line (case of line 6), not placed exactly at the same location.

[krassowski]

I was able to reproduce it, specifically, it looks that there are two copies of the marker in line 5:

and the second copy overhangs to line 6.

[krassowski]

Well, I am not sure if the issue is in the gutter code or in the chunking algorithm. In this case we get 6 conflict chunks:

And two of them have remoteFrom: 4 (so start at line 5, and the second of these leads to overhanging into line 6).

The also seem essentially identical:

First copy	Second copy

Is there any case when duplicate chunks are expected, or is this an error in chunking code?

[krassowski]

Is there any case when duplicate chunks are expected, or is this an error in chunking code?

@vidartf is this what you meant by "In certain cases overlapping chunks are not being considered properly overlapping." in issue #677? In that case I think this issue just becomes a duplicate of #677.

[vidartf]

There does seem to be a regression here compared to CM5 version. See this example diffing the files in ui-test/data/merge_test1:

CM5:

CM6:

Notice the extra arrow on the base version on line 5. You can also see the same for CM6 here:

https://github.com/jupyter/nbdime/blob/554c2d34882c77ce48e85586f5db8fce93ed80d1/ui-tests/tests/nbdime-merge-test1.spec.ts-snapshots/merge-test1-take-a-snapshot-at-opening-1-linux.png

[krassowski]

Yes, but it is not a bug in CM6 but a bug in how the chunks are calculated as per my comments above.

[krassowski]

Of course it still should be fixed, which may be best approached by writing a test case, but it may require more thought/context to understand why the chunking algorithm sometimes leads to duplicate chunks; or we could just add a simple workaround of de-duplicating them without worrying about the algorithm being occasionally wrong.

[vidartf]

To clarify, I am using CM5/CM6 as a shorthand for "current stable release" vs "current RC".

[vidartf]

(and while there are for sure some bugs in the current stable version's mergeview chunking algorithm, the one I point out above is a new bug in the RC version)