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Erlang for Visual Studio Code

This extension adds support for the Erlang language to Visual Studio Code, including editing, building and debugging.

New to the extension? Open Help > Welcome > Get started with Erlang: a walkthrough that checks your Erlang/OTP and rebar3 installation, then builds, tests and debugs your project.

Features at a glance

| Area | Features |

| Editing | Completion with snippets, hover docs, signature help, inlay hints, CodeLens, diagnostics while typing | | Highlighting | TextMate grammar + semantic highlighting from the syntax tree | | Navigation | Definition, declaration, type definition, implementations, references, document/workspace symbols, call & type hierarchy, highlight occurrences, links in -include | | Code actions | Quick fixes from compiler diagnostics, export/unexport, generate -spec, implement behaviour callbacks, extract function, inline variable, if ↔ case, sort -export | | Formatting | Document, selection and on-type formatting (erlfmt), folding, expand/shrink selection, rename | | Testing | EUnit and Common Test in the Testing view: run, debug, coverage | | Build | rebar3 commands, rebar3 tasks (compile, eunit, ct, dialyzer, release, shell, clean), Dialyzer warnings in Problems with PLT status in the status bar | | Debugger | Launch or attach to a running node; line, function, conditional, hit-count breakpoints, logpoints; variables, call stack, inline values | | AI agents | Opt-in, read-only MCP server inside the debugged node: an agent maps its applications, supervision trees, processes and ETS metadata | | Status | Language server state and OTP version in the status bar |

Editing support

• Syntax highlighting • Automatic indentation • Erlang IntelliSense • Shows errors and warnings dynamically while you type • Go To Definition/Peek Definition • Hover help for standard functions • Hover for project functions showing head clauses • CodeLens showing exported functions and references • InlayHints showing parameters name in function calls • disable by default : enable in configuration settings • limits : only works with locals calls

InlayHints in function calls

• showing parameter name when it doesn't match with caller var name

Semantic highlighting

Modules, functions, macros, variables, parameters, types, records and record fields are colored from the real syntax tree, on top of the TextMate grammar. OTP modules are flagged as defaultLibrary and functions listed in -deprecated as deprecated.

• disable with erlang.semanticTokensEnabled

Quick fixes and refactorings

Press Ctrl+. / Cmd+. on a diagnostic or on a selection:

• Quick fixes driven by compiler warnings/errors: • Prefix unused variable with _ • Export an unused function • Create a stub for an undefined function • Add a missing field to a record definition • Remove include of a missing file • Add missing -module(...) • Export / unexport a function, generate -spec from the function clauses • Implement missing callbacks for a -behaviour(...) • Refactorings: extract function from selection, inline variable, convert if ↔ case • Source actions: sort the -export list

Navigation

• Go to Symbol in Workspace (Ctrl+T / Cmd+T): functions, records, types, macros across the project • Go to Declaration, Go to Type Definition (from a -spec/type usage to its -type/-opaque) • Go to Implementations: from a -callback to every module implementing the behaviour • Call Hierarchy (incoming/outgoing calls) and Type Hierarchy (behaviour ↔ implementors) • Highlight all occurrences of the variable/function/record under the cursor • Clickable -include / -include_lib paths and URLs in comments

Formatting and folding

• Format document, format selection and format on type (., ;, ,, newline), powered by erlfmt • disable with erlang.formatterEnabled, line length with erlang.formattingLineLength • Folding of functions, clauses, case/receive/try, -export lists, comment blocks and %% region / %% endregion markers • Expand/shrink selection (Shift+Alt+→ / Shift+Alt+←) • Completion with snippets for function arguments, ? for macros, - for attributes

Testing

EUnit and Common Test tests are discovered by the language server and shown in the VS Code Testing sidebar:

• EUnit: *_test/0, *_test_/0 functions (including inside -ifdef(TEST)) • Common Test: *_SUITE.erl modules and their test cases • Run, Debug (breakpoints in tests) and Run with Coverage profiles • Per-test results with failure message and location, line coverage of the code under test shown in the editor gutter

Build

• Standard rebar3 is the default build tool, also rebar is supported. The rebar.config file should be placed in the root directory. • Build arguments are configurable, by default "compile" is used • You can override the default in configuration file (i.e. workspace settings)

rebar3 tasks

For every workspace folder with a rebar.config, Terminal > Run Task > rebar3 offers compile (the default build task), eunit and ct (test tasks), dialyzer, shell, clean, and release when relx is configured. Compiler errors and dialyzer warnings land in the Problems panel ($rebar3 and $rebar3-dialyzer problem matchers).

Customize them in tasks.json:

Dialyzer

Erlang: rebar dialyzer shows its warnings in the Problems panel. The status bar shows the state of the project PLT: none (the first run builds it, which is slow), stale (rebar.lock or rebar.config changed since it was built; rebar3 updates it incrementally on the next run) or ready. Click it to run dialyzer.

Debugger

• Variables List shows variables from the current scope • Call Stack shows Erlang processes and allows to control them with e.g. Pause and Continue • Standard commands Step Over, Step Into, Step Out supported • Full breakpoints support: • Regular breakpoints • Function Breakpoints: use format module:function/arity • Conditional Breakpoints • Hit-Count Breakpoints

Running debugger…

Description from the VS Code Marketplace listing.