Change Details

See PHI1740. Here's a small reproduction case: - Create a revision with these two diffs. - Intradiff them. ```name="Diff 1" commit 2715e92dd7b71db65639689932ef0a85ce9c9c2c Author: epriestley <git@epriestley.com> Date: Tue May 19 08:07:55 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..5179482 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +EEEE ``` ``` name="Diff 2" commit 8392e163b94c3de4ffb6293372e69c741d803d65 Author: epriestley <git@epriestley.com> Date: Tue May 19 08:08:14 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..d48e540 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +GGGG \ No newline at end of file ``` I think the critical pieces are: - Both changes should affect the last line of the file. - The starting state of the file should have no trailing newline. - The first change should add a trailing newline to the file. - The second change should remove it ("not add a trailing newline"). This ultimately fails in some very old highlighting code in `DifferentialHunkParser->parseHunksForHighlightMasks()`. The issue is roughly that each file has 4 real lines so we compute 4 offsets. However, the "No newline at end of file" lines add additional visual lines which aren't counted through properly. Internally, the intradiff ends up having "+/-" lines (from the change to the last line of the file) after it passes through a `\` line, and the counts are off.

See PHI1740. Here's a small reproduction case: - Create a revision with these two diffs. - Intradiff them. ```name="Diff 1" commit 2715e92dd7b71db65639689932ef0a85ce9c9c2c Author: epriestley <git@epriestley.com> Date: Tue May 19 08:07:55 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..5179482 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +EEEE ``` ``` name="Diff 2" commit 8392e163b94c3de4ffb6293372e69c741d803d65 Author: epriestley <git@epriestley.com> Date: Tue May 19 08:08:14 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..d48e540 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +GGGG \ No newline at end of file ``` I think the critical pieces are: - Both changes should affect the last line of the file and modify it to have different values. - The starting state of the file should have no trailing newline. - The first change should add a trailing newline to the file. - The second change should remove it ("not add a trailing newline"). This ultimately fails in some very old highlighting code in `DifferentialHunkParser->parseHunksForHighlightMasks()`. The issue is roughly that each file has 4 real lines so we compute 4 offsets. However, the "No newline at end of file" lines add additional visual lines which aren't counted through properly. Internally, the intradiff ends up having "+/-" lines (from the change to the last line of the file) after it passes through a `\` line, and the counts are off.

See PHI1740. Here's a small reproduction case: - Create a revision with these two diffs. - Intradiff them. ```name="Diff 1" commit 2715e92dd7b71db65639689932ef0a85ce9c9c2c Author: epriestley <git@epriestley.com> Date: Tue May 19 08:07:55 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..5179482 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +EEEE ``` ``` name="Diff 2" commit 8392e163b94c3de4ffb6293372e69c741d803d65 Author: epriestley <git@epriestley.com> Date: Tue May 19 08:08:14 2020 -0700 WIP diff --git a/no-newline.txt b/no-newline.txt index 957fef4..d48e540 100644 --- a/no-newline.txt +++ b/no-newline.txt @@ -1,4 +1,4 @@ AAAA -BBBB +FFFF CCCC -DDDD \ No newline at end of file +GGGG \ No newline at end of file ``` I think the critical pieces are: - Both changes should affect the last line of the file and modify it to have different values. - The starting state of the file should have no trailing newline. - The first change should add a trailing newline to the file. - The second change should remove it ("not add a trailing newline"). This ultimately fails in some very old highlighting code in `DifferentialHunkParser->parseHunksForHighlightMasks()`. The issue is roughly that each file has 4 real lines so we compute 4 offsets. However, the "No newline at end of file" lines add additional visual lines which aren't counted through properly. Internally, the intradiff ends up having "+/-" lines (from the change to the last line of the file) after it passes through a `\` line, and the counts are off.