PDDL (pddl-lsp)

Language support for the Planning Domain Definition Language (PDDL 3.1): error checking, navigation, rename, completion and formatting for domain and problem files. It's powered by pddl-lsp, a language server written in Rust, which comes with the extension. There's nothing else to install.

Features

Error checking

Mistakes are underlined as you type: every syntax error in a file, not just the first, and also:

• unknown predicates, functions, types, constants and objects,
• predicates and functions called with the wrong number of arguments,
• variables that no parameter list or quantifier declares,
• duplicate definitions.

A problem is checked against the domain named in its (:domain ...). That domain can be in the same file, in another open file, or in any .pddl file in the workspace.

Types, constants, predicates, functions, objects and parameters that nothing uses are shown faded.

A misspelled keyword, such as (:predicats ...), comes with a quick fix that corrects it.

Navigation

• Hover over a name to see its definition, such as (at ?t - truck ?p - place) for a predicate.
• Go to Definition (F12) jumps from a predicate in a problem's :init to its declaration in the domain, from a variable to its parameter, and so on.
• Find All References (Shift+F12) lists every use across domain and problem files.
• Outline and Go to Symbol, in the file or the whole workspace, list types, constants, predicates, functions, actions and objects.
• Lists that span several lines can be folded.

Editing

• Rename (F2) a predicate, function, type, constant, object, action, domain or variable everywhere it's used, including in other files.
• Completion suggests section and action keywords after :, requirements in :requirements, predicates and functions after (, types after -, objects and constants, and the variables in scope after ?.
• Signature help shows a predicate's parameters while you type its arguments.
• Inlay hints show parameter names before arguments, such as (at ?t: t1 ?p: home) in a problem's :init. An argument that already has the parameter's name gets none. Turn them off with editor.inlayHints.enabled.
• Snippets for a domain, problem, action, durative action, derived predicate, forall, exists and when: type the name, such as domain or :action, and pick the snippet.
• Format Document indents by nesting, puts each section and each :keyword value pair on its own line, and keeps short lists on one line. It keeps your comments and blank lines.

Highlighting

Syntax highlighting for keywords, variables, numbers and comments. Semantic highlighting then colors types, predicates, functions, actions, objects and variables differently, depending on what each name refers to.

PDDL embedded elsewhere is highlighted too:

• Markdown code blocks marked ```pddl.

• Strings in Rust, JavaScript, TypeScript and Python that follow a language=pddl comment, also inside Markdown code blocks:

  const DOMAIN: &str =
      // language=pddl
      r#"(define (domain d) (:predicates (at ?x)))"#;
  

  This covers Rust raw and normal strings, JavaScript and TypeScript template literals, and Python triple-quoted strings (# language=pddl). The string has to be the next one after the comment.

Only highlighting applies there: the Markdown preview, error checking and the other features above don't cover embedded PDDL.

Settings

The PDDL: Restart Language Server command restarts the server.

In Restricted Mode, only syntax highlighting is available. The server starts once you trust the folder, and a workspace can only set pddl.server.path after that.

Using a native server

The extension runs the server as WebAssembly, in Microsoft's WASI runtime, which VS Code installs along with this extension. A native build of the server skips that runtime, which may help with very large workspaces. To use one, install it with Rust:

cargo install --git https://github.com/sunsided/pddl-rs pddl-lsp

Then set pddl.server.path to pddl-lsp, or to the binary's full path if it's not on your PATH.

How domains are found

When the server starts, it reads every .pddl file in the workspace folders. It skips hidden folders, target and node_modules. It sees files change on disk, and for open files it always uses the editor's text. The bundled server can only read files inside the workspace folders, so a domain outside them is found only while it's open.

When several domains share a name, a problem uses the one in its own file. Otherwise it uses the one whose file path sorts first.

Limitations

• Argument types are not checked: (at truck1 truck2) passes even if the second parameter is a place.
• Requirements are not checked: using forall without :universal-preconditions is not reported.
• After a syntax error, checking resumes at the next section or action, so a section reports at most one syntax error.
• Formatting always uses two-space indents and an 80-column limit, and skips a file whose parentheses don't match.
• If another PDDL extension, such as jan-dolejsi.pddl, is also installed, both check .pddl files and you'll see duplicate diagnostics. Disable one of them for the workspace.

Feedback and contributing

Report bugs and ideas at github.com/sunsided/pddl-rs/issues. To build, test or publish the extension yourself, see CONTRIBUTING.md.