Ifc for VS Code

VS Code extension for editing IFC physical files (.ifc) — the text-based exchange format defined by ISO 10303-21, commonly used in building information modeling (BIM) and other STEP-based workflows.

Open any .ifc file and the extension activates automatically. No extra configuration is required.

Features

Language recognition

• Registers the Ifc language for files with the .ifc extension
• Applies the correct language mode, grammar, and editor behavior as soon as you open a file

Syntax highlighting

Colorizes the structure of ISO 10303-21 exchange files so you can scan large models more easily, including:

• File header and data section markers (ISO-10303-21;, HEADER;, DATA;, ENDSEC;, etc.)
• Entity instance references (#123)
• Keywords, strings, numbers, enumerations, and binary values
• Line (//) and block (/* */) comments

Smart editing

• Bracket and quote matching for ( ), [ ], { }, ', and "
• Auto-closing pairs when you type opening brackets or quotes
• Familiar comment toggling via Ctrl+/ / Cmd+/ (line comments) and block comment support

Language Server (LSP)

A built-in language server analyzes your file as you edit and integrates with standard VS Code features:

Server activity is logged in the Output panel under Ifc Language Server.

Validation layer status bar

When an .ifc file is the active editor, the status bar shows IFC n/3 — how many of the three validation tiers are enabled. Click it (or run IFC: Toggle Validation Layers) to open a quick pick:

Lexer/parser errors and unresolved # linker diagnostics are always reported regardless of these toggles. Changing a setting re-validates open .ifc files automatically.

You can also edit the same keys under Settings → Ifc.

Performance

During each validation pass the language server:

• Indexes inverse relations once when building the entity population (forward # references → inverse lists such as IsTypedBy). Entity WHERE rules query this index; they do not rescan the file.
• Caches attribute values (eval_cache) keyed by entity #id and attribute name so Types-layer DERIVE checks and Rules-layer Entity WHERE do not repeat the same DERIVE or parameter conversion work.

Turn off Types or Rules in the status bar if you want faster feedback while editing and only need structural checks.

EXPRESS schema validation (IFC4 / IFC4X3)

This extension validates .ifc files against the IFC4X3 EXPRESS schema (compiled from the official schema; files declaring IFC4, IFC4X3, or IFC4X3_DEV_* in FILE_SCHEMA are accepted).

Validation goes beyond STEP syntax and attribute typing — it evaluates EXPRESS constraints from the schema. The status-bar tiers map to these checks:

Always reported (not toggled): STEP parse errors and unresolved # linker diagnostics.

Optional $ values are treated as absent (no type-level WHERE on missing data). Derived * values are checked using computed DERIVE results where evaluators are available.

WHERE and RULE evaluation uses lazy short-circuiting: once a branch cannot be evaluated, later OR/AND branches in the same rule are skipped, and further WHERE rules on the same entity may be skipped when an eval-unknown is already recorded.

Diagnostics are anchored to the most specific location available: derived * tokens, other parameter tokens, or the declaring entity #id. Related entities in a reference chain (e.g. a parent IFCGEOMETRICREPRESENTATIONCONTEXT and its IFCGEOMETRICREPRESENTATIONSUBCONTEXT children) may each report issues so you can see the full impact radius.

Diagnostic codes (shown in the Problems panel):

Requirements

• Visual Studio Code 1.104.0 or later

Installation

1. Download or obtain the extension package (ifc-vscode.vsix).
2. In VS Code, open the Extensions view (Ctrl+Shift+X on Windows/Linux, Cmd+Shift+X on macOS).
3. Click the ... menu at the top of the Extensions sidebar.
4. Choose Install from VSIX... and select the .vsix file.
5. Reload VS Code if prompted.

After installation, open any .ifc file to start using syntax highlighting and language-server features.

Usage tips

• Use Go to Definition (F12) on a # entity reference to navigate to its declaration.
• Use Find All References (Shift+F12) to trace how an entity is referenced elsewhere in the file.
• Check the Problems panel (Ctrl+Shift+M / Cmd+Shift+M) for parse and EXPRESS validation issues.
• Click IFC n/3 in the status bar (when an .ifc file is active) to enable or disable Structure / Types / Rules validation tiers.
• Filter Problems by diagnostic code (e.g. ifc-entity-where, ifc-type-where) to focus on a class of errors.
• For troubleshooting, open View → Output and select Ifc Language Server from the dropdown.

Known limitations

• Support targets the ISO 10303-21 physical file format (.ifc text files). Other IFC representations (e.g. IFC-XML, IFC-ZIP) are not covered.
• Validation uses a compiled IFC4X3 schema; entities or types from other schema releases may not be recognized.
• DERIVE codegen covers all schema DERIVE slots; failed DERIVE/type-WHERE evaluation reports ifc-eval-unknown instead of silently skipping. Unresolved # references are reported by the linker only (not duplicated as eval-unknown). Optional $ / EXPRESS absent values still skip checks. Disable the Types tier to skip DERIVE and Type WHERE when validation feels slow on large files.
• Files with parse errors skip Global RULE and UNIQUE validation; remaining EXPRESS checks may still report eval-unknown on affected entities and parameters.
• This is an EXPRESS / schema validator, not a full BIM certification tool: no geometry kernel, IDS/MVD filtering, or clash detection.
• The extension focuses on single-file editing; cross-file workspace analysis depends on how your files are organized.