When "editor.autoClosingBrackets": true (or is effectively true via languageDefined), an extra trailing [ character is added.

Not familiar with Ionoide internals, but guessing there is some code that inserts a >] unconditionally, when it should instead only insert a > when editor.autoClosingBrackets is effectively true.
It seems like a bug in VSCode rather than Ionide. We just define autoClosingPairs in https://github.com/ionide/ionide-vscode-fsharp/blob/master/release/language-configuration.json, Ionide doesn't manually insert those closing characters.
Interestingly enough the issue has seemed to disappear (now it simply auto-completes the [ but not the < which is much more desired behavior). It would be nice if vscode would also pick up on your multi-character listings in the configuration you linked, but I'm sure they'll get around to fixing it in an update at some point :) Thanks for looking into this!
It sounds like a VSCode bug, but in case anyone else is getting as infuriated with this as I was:
.vscode directory, usually located in your %USERPROFILE% directory on Windows./extensions/ionide.ionide-fsharp-X.X.X/language-configuration.json["[<", ">]"], from the "autoClosingPairs" and "surroundingPairs" sectionsI'd be interested to know why the issue has gone for you - I was able to reproduce using a fresh install of VSCode insiders and Ionide.
As a workaround, I can get the behaviour I want for annotations by using the following in the "autoClosingPairs" section - whether it breaks behaviour elsewhere I don't know yet so mileage may vary...
"autoClosingPairs": [
...
["[<", ">"],
],
Oh hmm yeah it seems to have come back again for me as well. I'll leave it up to @Krzysztof-Cieslak whether or no they wan to re-open it here.
That workaround seems promising as well, since I don't think the [< character combination is used anywhere else...
Also looks like this vscode issue might be related... https://github.com/Microsoft/vscode/issues/583
It looks like https://github.com/microsoft/vscode/issues/72177 is the cause.
The https://github.com/microsoft/vscode/issues/72177 is in danger of being closed if it doesn't receive 20 upvotes in the next 60 days. Anyone who wants a true solution to this irritation should go upvote that bug so the VS Code bug bot doesn't auto-close it. (Edit: It's now at 22 votes and is safely ensconced in the backlog.)
That issue now has 20 votes :)
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It sounds like a VSCode bug, but in case anyone else is getting as infuriated with this as I was:
.vscodedirectory, usually located in your%USERPROFILE%directory on Windows./extensions/ionide.ionide-fsharp-X.X.X/language-configuration.json["[<", ">]"],from the"autoClosingPairs"and"surroundingPairs"sectionsI'd be interested to know why the issue has gone for you - I was able to reproduce using a fresh install of VSCode insiders and Ionide.
As a workaround, I can get the behaviour I want for annotations by using the following in the
"autoClosingPairs"section - whether it breaks behaviour elsewhere I don't know yet so mileage may vary...