Change:
const textAreaInputHost: ITextAreaInputHost = { getDataToCopy: (): ClipboardDataToCopy => { <del> return getDataToCopy(this._context.viewModel, this._selections, this._emptySelectionClipboard, this._copyWithSyntaxHighlighting); </del> <ins> return getDataToCopy(this._context.viewModel, this._modelSelections, this._emptySelectionClipboard, this._copyWithSyntaxHighlighting); </ins> }, getScreenReaderContent: (): TextAreaState => { if (this._accessibilitySupport === AccessibilitySupport.Disabled) {

Discussion:
Ctrl+C and the Copy context menu actions seem to place the wrong text on the clipboard. Cutting text removes it from the editor, but the contents are incorrect. note: the Insiders this happens on is currently frozen, but I also repro'd this on OSS
Possibly ? Also does this only happen in JS/TS files? Having trouble repoing
Ok was able to repo with a multi line selection. Seemed fixed by disabling the experimental edit context. can you try turning off that setting in oss
I'm repro'ing this, but turning off experimental edit context doesn't seem to help. I disabled experimental edit context by adding this to my user settings:
Annnd now I'm not reproducing.
You need to restart after changing the setting. Toggling it seems kind of wonky at the moment
That's what I assumed, and as such, I restarted (all windows closed) at least twice before deciding the disabling wasn't fixing the issue. But if there's issues around the toggle in general, it maybe it is more complex than just needing a restart. Maybe I needed to also like re-open the file or something like that?
I can also confirm that this does not fix it for me on OSS:
Hi all, thank you all for looking into this and apologies for this issue. Yes and I have debated a while whether we should make the setting change the edit context used immediately or be hot reloadable. We chose to make it so that you need to reload the window after the setting change for it to be applied. Perhaps now we need to add a notification to prompt the user to do it, or we could consider making it hot reloadable. We will look into what is causing this issue. To implement the edit context we changed a bit the copy paste controller, this is likely what is causing the issue.
Fyi we have where you can enlist a setting to cause a reload.
Great I will add the setting into that file.
Hi I am looking at the last screen recording you sent. When you reloaded the window. I was wondering what you copied? I saw you placed the cursor on a word, but there was no selection, so it seemed like nothing was copied, in which case the last copied text before that was pasted? Let me know if I am wrong.

Can I also ask the people who have seen this issue whether you have explicitly turned on the experimental edit context setting? Or did you just reload the window, and notice that the setting was turned on? The setting is supposed to be turned off by default.
The issue seems to be that we were passing in the view state selections instead of the model state selections to the logic that copies the code. The issue it seems was not related to the edit context logic per say, but was caused by the recent changes that were made when developing the edit context. When the edit context is disabled, copy pasting should be fixed. However we have discovered a new bug in the copy pasting when it is enabled, which we will investigate.
I had not explicitly turned it on before seeing it. I was coping selections, and what was put on the clipboard was whatever like four lines above, same number of characters into the line (if the line didn't have anything there, blank was put on the clipboard). I have a video I can share internally via Teams.
Nor I, I wasn't aware of the setting and it was not set to a non-default value in my settings files. Copying without a selection copies the entire line
Thanks all for the answers. We believe this issue should be fixed in the next insiders.