TeXlance

Pylance-style intelligence for LaTeX preambles in VS Code.

TeXlance reads your preamble and tells you whether the packages you asked for actually exist, resolving each name against your TeX installation (kpsewhich), your own extra search paths and the current workspace — then it helps you type those names in the first place.

TeXlance is a language server: a thin VS Code client (src/) talks to a server (server/) over LSP, and both share the editor-agnostic logic in core/.

Features

reportMissingPackages diagnostics

Commands are checked against the document folder, your extra paths, the workspace and finally kpsewhich (which is what pdflatex itself uses):

\documentclass{article}
\usepackage{amsmath, definitivamente-no-existe}

warning  Load the "definitivamente-no-existe" package could not be resolved
         TeXlance(reportMissingPackages)

• \usepackage{a, b, c} accepts a list and every entry is checked.
• \RequirePackage behaves identically.
• \documentclass{myclass} takes a single name and reports Load the "myclass" class could not be resolved.
• Commented-out lines are ignored, and the squiggle covers exactly the name.
• Only the preamble is inspected, and the scan stops at \begin{document}.

Completions

Names come from the kpathsea ls-R databases, so they reflect what is really installed, plus anything found in your workspace and extra paths.

Settings

{
  "texlance.analysis.extraPaths": ["/path/to/my/sty", "./vendor/tex"],
  "texlance.analysis.reportMissingPackages": "error"
}

Commands

• TeXlance: Refresh Package Index — re-scan ls-R databases, extra paths and the workspace.
• TeXlance: Show Output — open the language server log.
• TeXlance: Restart Language Server.

How resolution works

For \usepackage{foo} TeXlance looks for foo.sty in this order:

1. the directory of the document (TeX's .),
2. every texlance.analysis.extraPaths entry (recursive, depth-capped),
3. the workspace folders (recursive, depth-capped),
4. kpsewhich foo.sty, i.e. the real TeX search path.

Only names that survive all four steps are reported. All installed-package lookups for a document are batched into a single kpsewhich invocation, and kpsewhich is run with the document directory as its working directory, so \usepackage{local} next to your .tex file resolves exactly like it does for LaTeX itself.

Requirements

• VS Code 1.91 or newer.
• A TeX distribution providing kpsewhich (TeX Live, MacTeX, MiKTeX, …). Without it, TeXlance still resolves local files and extra paths and warns once that installed packages cannot be checked.

Development

npm install          # installs the workspaces (core, server) and the client
npm run build        # bundle dist/extension.js and dist/server.js
npm run watch        # rebuild on change
npm test             # typecheck + unit tests
npm run test:integration   # end-to-end tests in a real VS Code
npm run package      # produce texlance-0.1.0.vsix

Press F5 in VS Code to launch an Extension Development Host with the fixture workspace open — the Run Extension launch configuration does that, and Extension Tests runs the integration suite.

Layout

core/    @texlance/core  – preamble parsing, kpsewhich wrapper, index, resolution
server/  texlance-server – LSP server (diagnostics, completions)
src/     client          – VS Code extension entry point
test/    unit (Vitest) and integration (@vscode/test-electron) tests + fixtures

License

MIT