aspls — Answer Set Programming (Clingo)

Language support for Answer Set Programming in the ASP-Core-2 / Clingo dialect.

Works with .lp and .asp files in VS Code (and compatible editors).

Features

Feature	What you get
Run Clingo	Compute first or all answer sets (editor title buttons, context menu, Command Palette)
Results panel	Dedicated ASP → Results view: readable/copyable answer sets, errors, re-run
PATH or WASM	Bundled `clingo-wasm` by default; optional Clingo binary from PATH
Syntax highlighting	Atoms, variables, comments, directives, operators
Semantic highlighting	Different colors for facts, rule heads, rule bodies, constraints, `#show`, `#minimize`
Rainbow predicates	Optional underline color per predicate name (stable across the file)
Diagnostics	Syntax errors from the ASP parser; optional Clingo-backed checks
IntelliSense	Predicate completion from the current document
Hover	Name, arity, and head/body occurrence counts
Go to Definition	Jump to facts and rule heads
Find References	All occurrences of a predicate in the file

Install aspls from the Marketplace.
Make sure Python 3 is available on your PATH (or set aspls.pythonPath) for the language server.
Open a .lp file — the language server starts on first use and sets up a local venv automatically.
Click the play / run all icons in the editor title bar, or use the context menu / Command Palette:
- aspls: Compute first answer set
- aspls: Compute all answer sets
Results open in the ASP panel tab.

Optional: install Clingo on PATH for extra diagnostics (grounding/safety) and to use the system solver via aspls.clingo.usePath.

% Birds that are not penguins can fly
bird(tweety).
penguin(pingu).

flies(X) :- bird(X), not penguin(X).

#show flies/1.

Settings under aspls.clingo.* control models, threads, customArgs, and additionalFiles.

For multi-file programs and shared flags, create a workspace file (default name aspls.clingo.json) with:

aspls: Initialize Clingo config file

{
  "models": 0,
  "threads": 1,
  "customArgs": "",
  "additionalFiles": ["facts.lp"]
}

Then run aspls: Compute answer sets (config). Paths in additionalFiles are resolved relative to the active file, then the workspace root.

Setting	Default	Description
`aspls.pythonPath`	`""`	Path to Python 3. Empty = auto-detect `python3` / `python`.
`aspls.rainbowPredicates`	`true`	Rainbow underline per predicate name (role colors stay from semantic highlighting).
`aspls.clingo.usePath`	`false`	Use PATH / `aspls.clingo.path` instead of bundled WASM.
`aspls.clingo.path`	`""`	Optional absolute path to the Clingo binary.
`aspls.clingo.models`	`1`	Default model count for config runs (`0` = all).
`aspls.clingo.threads`	`1`	Clingo `-t` thread count.
`aspls.clingo.customArgs`	`""`	Extra CLI args (quoted tokens supported).
`aspls.clingo.additionalFiles`	`[]`	Extra program files to include.
`aspls.clingo.configFile`	`aspls.clingo.json`	Workspace config file name.

Semantic highlighting for ASP is enabled by default (editor.semanticHighlighting.enabled for [asp]).

Grammar covers a practical ASP-Core-2 / Clingo subset (facts, rules, constraints, aggregates, comparisons, common directives). Not every Clingo extension is parsed yet.
Diagnostics and navigation are per document (not whole workspace project graphs).
Bundled WASM supports common runs; some advanced CLI flags work more reliably with PATH Clingo.