ocaml-lsp
A language server implementing the Language Server Protocol (LSP) for OCaml, providing editor support like autocompletion and diagnostics.
What is ocaml-lsp?
OCaml-LSP is a language server that implements the Language Server Protocol (LSP) for the OCaml programming language. It provides IDE-like features such as autocompletion, hover documentation, go-to-definition, and code formatting directly within code editors that support LSP. It solves the problem of fragmented editor support for OCaml by offering a standardized, feature-rich tooling interface.
OCaml developers using editors like VS Code, Emacs, or Vim who want enhanced productivity features such as intelligent code assistance, real-time diagnostics, and refactoring tools.
Developers choose OCaml-LSP because it is the official, most comprehensive LSP implementation for OCaml, offering deep integration with the OCaml ecosystem (like Dune and Merlin), unique OCaml-specific features (e.g., destruct/construct code actions), and strong community support.
Overview
OCaml Language Server Protocol implementation
Use Cases
Best For
- Adding intelligent autocompletion and documentation hover to OCaml projects
- Integrating OCaml support into LSP-compatible code editors
- Refactoring OCaml code with go-to-definition and find references
- Using advanced code actions like generating pattern matches or constructing values by type
- Formatting OCaml source code automatically within the editor
- Debugging OCaml programs with real-time build diagnostics via Dune integration
Not Ideal For
- Projects using build systems other than Dune without Merlin integration
- Editors without LSP client support or plugins for OCaml-specific extensions
- Teams unwilling to run Dune in watch mode for real-time diagnostics
- Developers requiring full LSP standard compliance, including unsupported features like document coloring
Pros & Cons
Pros
Integrates with Dune's RPC for build diagnostics and file promotion, and leverages Merlin for accurate code analysis, as stated in the README's sections on Dune integration and relationship to Merlin.
Offers unique features like 'Destruct' for generating exhaustive pattern matches and 'Construct' for building expressions based on type, detailed in the 'Unusual features' section.
Provides experimental semantic token support for richer syntax coloring, configurable via environment variables like OCAMLLSP_SEMANTIC_HIGHLIGHTING, as explained in the semantic highlighting section.
Allows using underscores as typed placeholders during development, enabling incremental coding with well-typed substitutes, described in the typed holes subsection.
Cons
Does not implement some LSP requests such as 'textDocument/implementation' and 'textDocument/documentColor', limiting compatibility with editors expecting full protocol adherence.
Requires installation in every opam switch where it's used, and additional packages like ocamlformat for formatting support, adding to setup overhead as noted in the installation section.
Relies on Dune running in watch mode for accurate diagnostics and features like file promotion, which may not suit all workflows and can introduce latency, as mentioned in the Dune integration caveats.
Frequently Asked Questions
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