Multiple cursor copy-paste of non-selected lines pastes everything

[BartolHrg]

Type: Bug

1. have this contents of the file with multiple cursors at | (and nothing selected)

a|
b|

2. Copy (Ctrl + C)
3. Paste (Ctrl + V)

Expected:

a
a
b
b

Result:

aa
b

ba
b

If I were to individualy do the steps for each cursor (just 2 of them in this case), the result would be what's shown above (in the "Expected" region)

I have "editor.multiCursorPaste": "full", however, this setting should not apply in this case, since I don't have a single selection with multiple lines,
I have multiple copied items with single line in each.

I have slighltly modified VSCode installation, with only lineCommentCommand.ts modified to support tabs,
therefore, this also doesn't apply.

VS Code version: Code 1.102.0 (cb0c47c, 2025-07-09T22:10:34.600Z)
OS version: Windows_NT x64 10.0.26100
Modes: Unsupported

System Info

Item	Value
CPUs	13th Gen Intel(R) Core(TM) i7-13700H (20 x 2918)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	15.63GB (4.74GB free)
Process Argv	--crash-reporter-id 5235ac69-27f7-4b93-9f49-763295cb8572
Screen Reader	no
VM	0%

Extensions (37)

Extension	Author (truncated)	Version
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pynewline	Bar	1.1.1
arm	dan	1.7.4
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vscode-opencl	gal	0.8.6
path-autocomplete	ion	1.25.0
vscode-autohotkey-plus-plus	mar	6.7.1
Kotlin	mat	1.7.1
debug-tracker-vscode	mcu	0.0.15
memory-view	mcu	0.0.25
peripheral-viewer	mcu	1.4.6
rtos-views	mcu	0.0.7
rainbow-csv	mec	3.20.0
workspace-storage-cleanup	meh	1.11.5
git-graph	mhu	1.30.0
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python	ms-	2025.4.0
vscode-pylance	ms-	2025.4.1
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cpptools	ms-	1.22.11
extension-test-runner	ms-	0.0.12
hexeditor	ms-	1.11.1
powershell	ms-	2025.2.0
incrementor	nms	1.0.3
word-count	Oli	0.1.0
subtitles-editor	pep	1.1.7
ActiveFileInStatusBar	Ros	1.0.3
markdown-preview-enhanced	shd	0.8.18
pdf	tom	1.2.2
gnu-mapfiles	tro	1.1.0
luna-paint	Tyr	0.17.0
vscode-todo-highlight	way	1.0.5
change-case	wma	1.0.0
linkerscript	Zix	1.0.4

(1 theme extensions excluded)

A/B Experiments

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[Shiv10122003]

Hey bartol I have read the docs thoroughly and I understood how to resolve the documentation please assign respective issue to me

[BartolHrg]

I think I have identified the issue.
Problem is ./src/vs/editor/common/viewModel/viewModelImpl.ts:969 (inside ViewModel.getPlainTextToCopy)

This assumes that emptySelectionClipboard is true (that was originally an assumption, and I didn't even know this option existed in settings until I inspected the code).
This option causes that, when nothing is selected, VSCode copies the whole line.

The method ViewModel.getPlainTextToCopy returns either string or string[].
If it returns string[], it is treated as copy from multiple cursors (and is assigned to multicursorText).
If it returns just a string, it is treated as a single selection (and multicursorText is null)

If all selections are empty, the method returns just a string, and it is treated as if there weren't multiple cursors, which is incorrect behavior.
If all selections are empty, the result should be the array of the lines.

What I suggest to be done is:

1. Reduce if on the line 961 to just this, and let the code below correctly handle empty selections.

if (!hasNonEmptyRange) {
	// all ranges are empty
	if (!emptySelectionClipboard) {
		return '';
	}
}

2. On line 987, change to

result.push(this.model.getLineContent(modelLineNumber) + newLineCharacter);

Because behavior of copying empty lines should be consistent.  
If a user copied the whole line, it should copy `\n` too  
(most of the time, there is no mixing of empty and nonempty selections anyway).  

3. If you don't want to implement point 1., then I suggest that on the aforementioned line 969
   result becomes an array and lines are pushed instead of concatenated.

[BartolHrg]

This odd behavior was added in 845c25c while fixing #11007.
I think that (11007) is a non issue, since there is already a way to copy a block of code to another place:
Select that lines with singular selection and copy/cut them.
That is the easiest/most straightforward way,
But I don't see why multiple cursors and Ctrl+X wouldn't work today (I don't really know how code looked when this was implemented).

[alexdima]

@BartolHrg I think this might have been fixed in the meantime, I can't reproduce:

CleanShot.2025-11-14.at.19.31.20.mp4