IFC-Language-Server

ifc-language-server is a lightweight Language Server Protocol server for IFC STEP P21 files (ISO 10303). It provides schema-aware IFC editing features, local STEP id navigation, diagnostics, semantic tokens, and editor assistance for IFC entity arguments.

Current Capabilities

• Hover on IFC entity names such as IFCWALL and IFCSPACE
• Hover preview for entity references such as #123
• Derived * hover for IfcSIUnit and IfcGeometricRepresentationSubContext
• Go-to-definition for local entity references
• Find-references within the current document
• Document highlight for local STEP ids such as #123
• Signature help for IFC entity parameter lists
• Document symbols for editor Outline, breadcrumbs, and go-to-symbol navigation
• IFC STEP boilerplate via !ifc / !!ifc / !!!ifc completions and empty-document code actions
• Range-based semantic tokens for syntax highlighting
• Schema-aware diagnostics for:
  • invalid local reference targets
  • primitive datatype mismatches
  • invalid enumeration values
  • incorrect entity argument counts
  • invalid $ / * usage for attributes

Supported IFC Schema Versions

Bundled entity documentation is currently included for:

• IFC 2.3.0.1
• IFC 4.0.2.1
• IFC 4.3.2.0

Current Limitations

• Single-document navigation only
• Full-document reparsing on open and change
• Diagnostics currently focus on entity-instance argument validation, not full EXPRESS rule evaluation
• No general completion, rename, or formatting support
• Code actions are currently limited to IFC boilerplate insertion for empty documents
• The LSP server provides range-based semantic tokens, but does not provide full-document semantic-token or TextMate grammar support

Installation

Editor integrations

Extensions for VSCode and Zed are available for local installation (though still under development):

• VSCode

• Zed

Manual

Release binaries are available on the Releases page.

After downloading a release:

1. Place the ifc-language-server binary somewhere on your PATH, or configure your editor to point to the absolute binary path.
2. Register it as the language server for IFC STEP files in your editor or IDE.

Development

Prerequisites

• Rust (stable): https://www.rust-lang.org/tools/install
• An editor with LSP client support such as Helix, Neovim, VS Code, or Zed

Build

Build a release binary with:

cargo build --release

Configuration

The server accepts configuration through LSP initializationOptions.

Supported options:

• overwriteExpSchemaWithLocal

  • A single path to a local .exp file.
  • If set, the server always uses that schema for diagnostics and hover, regardless of the FILE_SCHEMA(...) declared in the IFC file.
  • If the forced schema does not match the schema declared in the IFC file, the server shows a warning and continues with the forced schema.

• addLocalSchemaToSelection

  • A list of local paths.
  • Each path may point to either:
    • a single .exp file
    • a directory containing .exp files
  • These schemas are added to the server's schema selection pool.
  • When an IFC file declares a schema name that is not bundled, the server checks the configured local schemas for an exact SCHEMA ...; name match and loads the matching schema on demand.

• astFileSizeLimitMb

  • Maximum file size in MiB for AST-backed features.
  • Defaults to 70.
  • Files above this limit keep basic hover/navigation, document highlight, signature help, and semantic tokens available, but skip schema diagnostics and derived-value hover.

• semanticTokensEnabled

  • Enables range-based semantic tokens.
  • Defaults to true.

Configuration changes currently require restarting the server.

Example initializationOptions:

{
  "overwriteExpSchemaWithLocal": "/Users/alice/dev/express/IFC4x2.exp",
  "astFileSizeLimitMb": 128,
  "semanticTokensEnabled": true,
  "addLocalSchemaToSelection": [
    "/Users/alice/dev/express/IFC4x1.exp",
    "/Users/alice/dev/express/custom-schemas"
  ]
}

Grammar And Parser

This project depends on the published tree-sitter-ifc crate for IFC parsing.

If you are developing the grammar itself, work in the tree-sitter-ifc repository and publish a new crate version when needed. During local development, you can temporarily override the crates.io dependency with a [patch.crates-io] entry that points at a local checkout.

Documentation

• Architecture
• Coding Guidelines
• Diagnostics Capabilities
• Requirements

Contributing

Contributions are welcome. Read Architecture and Coding Guidelines before submitting a PR.

License

MIT