feat: add MinML Language Server (LSP) with VSCode client integration

[phamelink]

feat: add MinML Language Server (LSP) with VSCode client integration

Summary

This PR implements a full Language Server Protocol (LSP) server for MinML and wires it into the VSCode extension as an LSP client.

What's new:

• A Go LSP server (go/markup/minml/lsp/) backed by glsp and the go-tree-sitter CGo bindings
• Diagnostics — parse errors and missing nodes from the tree-sitter AST are surfaced as real-time error squiggles
• Hover — hovering over a tag name shows its HTML description (sourced from a bundled HTMLElements map); hovering over attribute names shows the attribute name
• Completions — tag name completions drawn from the full set of HTML elements; attribute completions fire when inside a {…} attribute block (including incomplete/ERROR parses where the closing } hasn't been typed yet)
• A document store that keeps the most-recently-parsed tree-sitter Tree per open URI, updated on every textDocument/didOpen and textDocument/didChange notification
• The VSCode extension now starts the minml-lsp binary as a child process and connects to it as an LSP client via stdio, with a configurable minml.lspPath setting and an opt-in minml.debug flag
• Updated tree-sitter highlight queries and a new indents.scm for auto-indentation support
• Makefile targets: gen-parser (regenerates the C parser from grammar.js) and build-lsp (compiles the Go LSP binary)

Design decisions

glsp over a hand-rolled protocol layer — glsp provides typed handlers for every LSP 3.16 method, handles the JSON-RPC framing, and lets the server declare capabilities at Initialize time without boilerplate. It was the cleanest way to get a correct server fast.

Full document sync — the server advertises TextDocumentSyncKindFull and re-parses the entire document on every change. MinML files are small and tree-sitter parses are sub-millisecond, so incremental sync would add complexity for no measurable benefit.

LSP binary path resolution — the extension looks up the binary in order: user config (minml.lspPath) → extension directory (used by make vscode-live-preview which copies the binary next to the .vsix) → system PATH. This means it works both for end-users who install the packaged extension and for developers iterating locally.

Completions inside incomplete parses — when a user types { to start an attribute block but hasn't closed it yet, tree-sitter produces an ERROR node. The completion handler walks up the ancestor chain looking for either a valid attr_block or an ERROR node containing a literal { child, so attribute suggestions fire immediately even before the block is syntactically complete.

Diagnostics from tree-sitter ERROR/MISSING nodes — rather than writing a separate validator, parse errors are read directly from the tree-sitter CST. The server stops recursing into ERROR subtrees to avoid flooding the diagnostics list with cascading phantom errors from a single typo.

How to test

Prerequisites: Go ≥ 1.21, Node.js, tree-sitter CLI, a C toolchain (for the CGo tree-sitter bindings).

# 1. Generate the C parser from grammar.js
make gen-parser

# 2. Build the LSP binary and copy it next to the extension
make build-lsp

# 3. Open the VSCode extension in the Extension Development Host
cd dev/vscode/minml-preview
npm install
# Press F5 in VSCode (or use the "Run Extension" launch config)

Manual tests to run in the Extension Development Host:

Scenario	Expected
Open a .m file with a typo (e.g. [div without ])	Red squiggle on the error range
Type [ then start a tag name	Completion list of HTML elements appears
Type [div{ inside an element	Attribute completions appear immediately
Hover over div in [div]…[/div]	Tooltip shows the HTML div description
Fix the typo	Squiggle disappears on the next keystroke
Set minml.lspPath to a custom binary path in settings	Extension uses that binary instead

[AntoineBastide47]

Overall nice looking PR, just some slight changes needed.

The ide I use for golang is GoLand from Jetbrains, and it tells me that the code has a lot of unused parameters and some slice declaration warnings (these aren't code errors, just flag that should be fixed for better go code).

Also when I try and build the LSP I get this error:

make build-lsp
go build -o minml-lsp ./go/markup/minml/cmd/lsp/
# github.com/dedis/matchertext/go/markup/minml/lsp
go/markup/minml/lsp/server.go:39:37: s.SemanticTokensFull undefined (type *Server has no field or method SemanticTokensFull)
go/markup/minml/lsp/server.go:58:21: undefined: tokenTypes
go/markup/minml/lsp/server.go:59:21: undefined: tokenModifiers
make: *** [build-lsp] Error 1