feat: resolve variables in custom path settings

[silverstein]

Summary

Fixes #721.

This updates the extension to resolve common VS Code variables in path-like Biome settings before they are used locally or returned to the language server.

What changed

• biome.lsp.bin and deprecated biome.lspBin now expand variables such as ${workspaceFolder}, ${workspaceFolder:name}, ${userHome}, ${cwd}, and ${env:NAME} before path resolution.
• biome.configurationPath now goes through the same expansion when the language server requests biome settings via workspace/configuration.
• The same configuration middleware also normalizes direct workspace/configuration requests for biome.configurationPath, biome.lsp.bin, and biome.lspBin, so local path resolution and server-side settings stay aligned.
• Added a changeset because this is a user-facing extension behavior fix.

Why this fixes the issue

Before this change, the extension treated configured paths as literal strings. That meant settings like:

• "biome.lsp.bin": "${userHome}/.../biome"
• "biome.configurationPath": "${workspaceFolder}/biome.json"

were passed through without interpolation, so the binary lookup and config lookup failed even though the expanded paths were valid.

Verification

Repo checks

• pnpm exec biome check src/session.ts src/utils.ts .changeset/five-apricots-resolve.md
• pnpm run typecheck
• pnpm run build
• npx -y node@24.14.1 ./node_modules/@vscode/vsce/vsce package --out biome.vsix

Note: pnpm run package failed under local Node 25 because of a vsce dependency/runtime mismatch, but packaging succeeded under the repo's pinned Node 24.14.1 from .node-version.

Manual extension-host validation

Launched a clean VS Code extension-development window with isolated --user-data-dir and a throwaway workspace configured with:

• "biome.lsp.bin": "${workspaceFolder}/node_modules/.bin/biome"
• "biome.configurationPath": "${workspaceFolder}/biome.json"

Observed in the extension logs that:

• biome.lsp.bin was expanded and successfully unshimmed from the workspace-relative path to the real bundled Biome binary.
• The workspace/configuration response contained "configurationPath": "/tmp/biome-vscode-test-ws/biome.json" as an absolute path, not the raw ${workspaceFolder} string.

AI assistance

I used Codex (GPT-5.4, high reasoning) to help with implementation and drafting, then reviewed the code, fixed issues found during an adversarial follow-up review, and ran the verification above.

[changeset-bot]

🦋 Changeset detected

Latest commit: fabfc86

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
biome	Minor

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Click here if you're a maintainer who wants to add another changeset to this PR

[nhedger]

Suggested change

	"biome": patch
	"biome": minor

[silverstein]

Makes sense to me. I was thinking of it as a bug fix for existing settings, but I’m happy to treat the user-visible behavior change as minor here. I’ll switch it over.