Fix PowerShell parsing for standalone -- tokens

[Ingvar Stepanyan (RReverser)]

This PR fixes an issue where VSCode would keep asking for approvals for any commands using -- for argument separation, even if such commands have already been included in the autoApprove patterns.

This is caused by treesitter being unable to parse this separator and VSCode forcing explicit approval for any unparsed commands.

• Fixes chat.tools.terminal.autoApprove does not work for npm exec -- ... commands #325635.
• Fixes AutoApprove rules are not honored under Default Approvals for terminal commands #324059.
• Fixes Terminal auto-approval fails for git diff -- <path> despite "git diff" allow rule #321748.

Inspired by a similar fix in #310839.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

Anthony Kim (@anthonykim1)

Matched files:

• src/vs/workbench/contrib/terminalContrib/chatAgentTools/browser/treeSitterCommandParser.ts
• src/vs/workbench/contrib/terminalContrib/chatAgentTools/test/electron-browser/treeSitterCommandParser.test.ts

[Copilot]

🔵 Needs a closer look

Terminal auto-approval parsing is security-sensitive and warrants final human review of PowerShell edge cases.

Pull request overview

Fixes PowerShell parsing of standalone -- tokens used by native CLI tools.

Changes:

• Masks standalone -- tokens before tree-sitter parsing while preserving offsets.
• Adds regression coverage for Git pathspecs and npm exec.

File summaries

File	Description
treeSitterCommandParser.ts	Extends PowerShell native-argument masking.
treeSitterCommandParser.test.ts	Adds standalone -- parsing tests.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[iket0731]

Hi Ingvar Stepanyan (@RReverser)

I was also looking into the standalone -- issue in PowerShell. I noticed one concern while reading your PR.

pwshStandaloneDoubleDashRegex replaces standalone -- with __ regardless of context. For example:

$val --  ->  $val __

In my local testing, Tree-sitter parses the original $val -- successfully, but reports an error for $val __. This means that cases where -- is not being used as a native CLI argument separator could become unanalyzable, even though they were previously parsed successfully.

Rather than masking every standalone --, it may be worth revisiting the masking approach so that it only applies when -- is used as a native CLI argument separator. Sharing this in case it is useful.

[Ingvar Stepanyan (RReverser)]

Tree-sitter parses the original $val -- successfully, but reports an error for $val __.

Ugh it just keeps getting weirder. So tree sitter is fine with trailing -- but not a standalone one?

But yeah, good catch if so, I'll update the PR.

[iket0731]

tree-sitter-powershell accepts -- as a decrement operator in PowerShell syntax, but reports it as an error when it appears in a command. (This appears to be a bug or limitation of tree-sitter-powershell.)
This behavior does not depend on the position of --.

$val --  # OK
-- $val  # OK
git diff --  # Error
git diff -- file.txt  # Error

[Ingvar Stepanyan (RReverser)]

Ugh that's trickier to distinguish. I guess an easy option might be to replace -- with (double space instead of __) - in most cases they are equivalent, and it would preserve $val -- -> $val and -- $val -> $val as valid syntax too.

[Ingvar Stepanyan (RReverser)]

I guess an easy option might be to replace -- with (double space instead of __) - in most cases they are equivalent, and it would preserve $val -- -> $val and -- $val -> $val as valid syntax too.

Did this. I think it's conceptually more correct too - standalone -- is normally used as a whitespace-style separator between whole arguments, which is why the --flag -> __flag trick doesn't apply here.