This table gives a summary of the features that HLS supports. Many of these are standard LSP features, but a lot of special features are provided as code actions and code lenses.
| Feature | LSP method |
|---|---|
| Diagnostics | textDocument/publishDiagnostics |
| Hovers | textDocument/hover |
| Jump to definition | textDocument/definition |
| Jump to type definition | textDocument/typeDefinition |
| Find references | textDocument/references |
| Completions | textDocument/completion |
| Formatting | textDocument/formatting, textDocument/rangeFormatting |
| Document symbols | textDocument/documentSymbol |
| Workspace symbols | workspace/symbol |
| Call hierarchy | textDocument/prepareCallHierarchy, callHierarchy/incomingCalls, callHierarchy/outgoingCalls |
| Highlight references | textDocument/documentHighlight |
| Code actions | textDocument/codeAction |
| Code lenses | textDocument/codeLens |
| Selection range | textDocument/selectionRange |
| Rename | textDocument/rename |
| Semantic tokens | textDocument/semanticTokens/full |
The individual sections below also identify which HLS plugin is responsible for providing the given functionality, which is useful if you want to raise an issue report or contribute! Additionally, not all plugins are supported on all versions of GHC, see the plugin support page for details.
Provided by: ghcide
Provides errors and warnings from GHC as diagnostics.
Provided by: hls-hlint-plugin
Provides hlint hints as diagnostics.
Provided by: hls-stan-plugin
Provides Stan hints as diagnostics.
Provided by: hls-cabal-plugin
Provides errors and warnings from Cabal as diagnostics
Provided by: ghcide
Type information and documentation on hover, including from local definitions.
Provided by: hls-explicit-fixity-plugin
Provides fixity information.
Provided by: ghcide
Jump to the definition of a name.
Known limitations:
- Only works for local definitions.
Provided by: ghcide
Known limitations:
- Only works for local definitions.
Provided by: ghcide
Find references to a name within the project.
Provided by: ghcide
- Completion of names from qualified imports.
- Completion of names from non-imported modules.
Provided by: hls-pragmas-plugin
Completions for language pragmas.
Format your code with various Haskell code formatters.
| Formatter | Provided by |
|---|---|
| Floskell | hls-floskell-plugin |
| Fourmolu | hls-fourmolu-plugin |
| Ormolu | hls-ormolu-plugin |
| Stylish Haskell | hls-stylish-haskell-plugin |
Format your cabal files with a cabal code formatter.
| Formatter | Provided by |
|---|---|
| cabal-fmt | hls-cabal-fmt-plugin |
Provided by: ghcide
Provides listing of the symbols defined in a module, used to power outline displays.
Provided by: ghcide
Provides listing of the symbols defined in the project, used to power searches.
Provided by: hls-call-hierarchy-plugin
Shows ingoing and outgoing calls for a function.
Provided by: ghcide
Highlights references to a name in a document.
Provided by: hls-pragma-plugin
Code action kind: quickfix
Inserts missing pragmas needed by GHC.
Provided by: hls-hlint-plugin
Code action kind: quickfix
Applies hints, either individually or for the whole file. Uses apply-refact.
Known limitations:
- May have strange behaviour in files with CPP, since
apply-refactdoes not support CPP. - The
hlintexecutable by default turns on many extensions when parsing a file because it is not certain about the exact extensions that apply to the file (they may come from project files). This differs from HLS which uses only the extensions the file needs to parse the file. Hence it is possible for thehlintexecutable to report a parse error on a file, but thehlintplugin to work just fine on the same file. This does mean that the turning on/off of extensions in the hlint config may be ignored by thehlintplugin. - Hlint restrictions do not work (yet). This PR should enable that functionality, but this requires a newer version of hlint to be used in HLS.
Provided by: hls-explicit-imports-plugin
Code action kind: quickfix.literals.style
Make import lists fully explicit (same as the code lens).
Provided by: hls-explicit-imports-plugin
Code action kind: quickfix.import.refine
Refines imports to more specific modules when names are re-exported (same as the code lens).
Provided by: hls-qualify-imported-names-plugin
Code action kind: quickfix
Rewrites imported names to be qualified.
For usage see the readme.
Provided by: hls-class-plugin
Code action kind: quickfix
Adds placeholders for missing class methods in a class instance definition.
Provided by: hls-retrie-plugin
Code action kind: refactor.extract
Extracts a definition from the code.
Provided by: hls-retrie-plugin
Code action kind: refactor.inline
Inlines a definition from the code.
Provided by: hls-splice-plugin
Code action kind: refactor.rewrite
Evaluates a Template Haskell splice and inserts the resulting code in its place.
Provided by: hls-alternate-number-format-plugin
Code action kind: quickfix.literals.style
Converts numeric literals to different formats.
Provided by: hls-change-type-signature-plugin
Code action kind: quickfix
Change/Update a type signature to match implementation.
Status: Until GHC 9.4, the implementation is ad-hoc and relies on GHC error messages to create a new signature. Not all GHC error messages are supported.
Known Limitations:
- Not all GHC error messages are supported
- Top-level and Function-local bindings with the same names can cause issues, such as incorrect signature changes or no code actions available.
Provided by: hls-refactor-plugin
Code action kind: quickfix
Add an undefined variable as an argument to the top-level binding.
Provided by: hls-gadt-plugin
Code action kind: refactor.rewrite
Convert a datatype to GADT syntax.
Provided by: hls-explicit-record-fields-plugin
Code action kind: refactor.rewrite
Expand record wildcards, explicitly listing all record fields as field puns.
Provided by: hls-cabal-plugin
Code action kind: quickfix
Correct common misspelling of SPDX Licenses such as BSD-3-Clause.
Provided by: ghcide
Shows the type signature for bindings without type signatures, and adds it with a click.
Provided by: hls-eval-plugin
Evaluates code blocks in comments with a click. Tutorial.
Known limitations:
- Standard input is shared with HLS, so e.g.
getLinebreaks the connection to server. - Standard (error) output is not captured.
- While similar to doctest, some of its features are unsupported, see Differences with doctest.
Provided by: hls-explicit-imports-plugin
Shows fully explicit import lists and rewrites them with a click (same as the code action).
Provided by: hls-explicit-imports-plugin
Shows refined imports and applies them with a click (same as the code action).
Provided by: hls-module-name-plugin
Shows module name matching file path, and applies it with a click.
Provided by: hls-code-range-plugin
Provides haskell specific shrink/expand selection support.
Provided by: hls-code-range-plugin
Provides haskell specific Folding support.
Provided by: hls-rename-plugin
Provides renaming of symbols within a module. Experimental cross-module renaming can be enabled via the configuration.
Known limitations:
- Cross-module renaming requires all components to be indexed, which sometimes causes partial renames in multi-component projects.
Provided by: hls-semantic-tokens-plugin
Provides semantic tokens for each token in the source code to support semantic highlighting.
Provided by: hls-overloaded-record-dot-plugin
Code action kind: refactor.rewrite
Rewrites record selectors to use overloaded dot syntax
The following features are supported by the LSP specification but not implemented in HLS. Contributions welcome!
| Feature | Status | LSP method |
|---|---|---|
| Signature help | Unimplemented | textDocument/signatureHelp |
| Jump to declaration | Unclear if useful | textDocument/declaration |
| Jump to implementation | Unclear if useful | textDocument/implementation |
| Linked editing | Unimplemented | textDocument/linkedEditingRange |
| Document links | Unimplemented | textDocument/documentLink |
| Document color | Unclear if useful | textDocument/documentColor |
| Color presentation | Unclear if useful | textDocument/colorPresentation |
| Monikers | Unclear if useful | textDocument/moniker |