Diff editor closes when closing left hand side editor in other tab

[MarekLew]

Issue Type: Bug

1. Create two files in folder:

mkdir A
echo a1>A/a.txt
echo a2>A/b.txt

2. Open folder A and file b.txt

code A
code A/b.txt

3.a. compare A/b.txt to A/a.txt
CRT+SHIFT+P
File: Compare Active file With ...
select a.txt
3.b. compare A/b.txt to A.a.txt from command line
code --diff A/b.txt A/a.txt
4. clouse file b.txt

Then diff tab is closer

VS Code version: Code 1.23.1 (d0182c3, 2018-05-10T16:04:33.747Z)
OS version: Linux x64 4.13.0-43-generic
and on windows 10

System Info

Item	Value
CPUs	Intel(R) Core(TM) i3-2330M CPU @ 2.20GHz (4 x 903)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: disabled_software video_decode: unavailable_software video_encode: enabled vpx_decode: unavailable_software webgl: enabled webgl2: enabled
Load (avg)	1, 0, 0
Memory (System)	3.77GB (0.91GB free)
Process Argv	/usr/share/code/code A
Screen Reader	no
VM	0%

Extensions (38)

Extension	Author (truncated)	Version
bracket-pair-colorizer	Coe	1.0.55
vs-treeview	DaG	2.5.0
vsc-material-theme	Equ	2.1.0
virtual-folders	Gru	0.1.2-b1
taskmarks	Nor	0.6.1
Bookmarks	ale	0.19.1
project-manager	ale	0.25.2
code-gnu-global	aus	0.2.2
spellright	ban	2.5.0
npm-intellisense	chr	1.3.0
python-snippets	cst	0.2.0
jshint	dba	0.10.18
vscode-eslint	dba	1.4.10
gitlens	eam	8.3.3
tslint	eg2	1.0.30
vscode-npm-script	eg2	0.3.4
LogFileHighlighter	emi	2.4.0
git-project-manager	fel	1.6.1
favorites	kdc	1.4.4
vscode-gist	ken	1.2.0
git-tree-compare	let	1.2.1
cmake-tools-helper	mad	0.2.1
MagicPython	mag	1.0.12
vscode-checkpoints	mic	1.0.1
vscode-clang	mit	0.2.2
quicksnippet	mou	0.0.1
hg	mrc	1.2.3
python	ms-	2018.4.0
cpptools	ms-	0.17.4
vscode-code-outline	pat	0.2.1
annotator	ryu	0.11.0
partial-diff	ryu	1.1.0
guides	spy	0.9.1
python	tht	0.2.3
cmake	twx	0.0.17
cmake-tools	vec	0.11.1
gitflow	vec	1.2.1
local-history	xyz	1.6.2

Does this issue occur when all extensions are disabled?: Yes

[bpasero]

Happens somewhere around here:
https://github.com/Microsoft/vscode/blob/eb1d9729cd6104019f34b05099e509ee33ef3502/src/vs/workbench/browser/parts/editor/editorGroupView.ts#L482

[MarekLew]

@bpasero I found problem in (updateResourceMap ):
https://github.com/Microsoft/vscode/blob/eb1d9729cd6104019f34b05099e509ee33ef3502/src/vs/workbench/common/editor/editorGroup.ts#L522
please add code like this at the begin line in updateResourceMap :

		if (editor instanceof SideBySideEditorInput) {
			this.updateResourceMap(editor.details, remove);
		}

EditorGroup.mapResourceToEditorCount don`t contains left-hand side resorce from diff editor. For right side is used getResource but left side is ignored.

[bpasero]

I appreciate the investigation but the fix is more involved than just that, that is why I did not add the "help wanted" label.

[MarekLew]

No problem. I just pointed out that the bug is not where you marked it(not only when editor clause but open). In my opinion bug is in counting of resources.
It works for me :)