EBNF Syntax Highlighting and Intellisense
A VS Code extension for editing EBNF grammar files with full IDE support.
EBNF (Extended Backus-Naur Form) is a notation for defining the syntax of programming languages and data formats. This extension follows the ISO/IEC 14977 standard.
Features
Core Editing
- Syntax Highlighting -- Colors for rule names, strings, comments, operators, and special sequences
- Snippets -- Quick templates for common EBNF patterns (type
rule, grp, opt, etc.)
- Auto-closing -- Automatically closes brackets, quotes, and comments
- Folding -- Collapse rules and comments to focus on specific parts of your grammar
Navigation
- Go to Definition -- Click a rule name to jump to where it's defined (F12)
- Find References -- See everywhere a rule is used (Shift+F12)
- Document Symbols -- View all rules in the outline panel (Ctrl+Shift+O)
- Workspace Symbols -- Search for rules across all EBNF files in your project (Ctrl+T)
Validation
- Error Detection -- Highlights syntax errors like missing semicolons or unmatched brackets
- Undefined Rules -- Warns when you reference a rule that doesn't exist
- Duplicate Rules -- Flags rules defined more than once
- Unused Rules -- Hints when a rule is defined but never referenced
Refactoring
- Rename -- Change a rule name everywhere it appears (F2)
- Quick Fixes -- Click the lightbulb to create missing rules automatically
- Semantic Highlighting -- Different colors for rule definitions vs references
Cross-file Support
- Multi-file Navigation -- Jump to definitions in other EBNF files
- Workspace References -- Find usages across your entire project
Installation
Install from the VS Code Marketplace or search for "EBNF" in VS Code extensions.
To build from source:
bun install
bun run package
code --install-extension vscode-ebnf-intellisense-*.vsix
Usage
Open any .ebnf or .bnf file. The extension activates automatically.
Example EBNF file
(* A simple expression grammar *)
expression = term, { ("+"|"-"), term };
term = factor, { ("*"|"/"), factor };
factor = number | "(", expression, ")";
number = digit, { digit };
digit = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9";
Markdown Support
Use ebnf code blocks in Markdown files for syntax highlighting:
```ebnf
rule = "example";
```
Settings
| Setting |
Default |
Description |
ebnf.diagnostics.enable |
true |
Enable or disable all diagnostics |
ebnf.diagnostics.unusedRules |
true |
Show hints for unused rules |
ebnf.parser.spacedIdentifiers |
false |
Allow spaces in rule names per ISO 14977 section 6.2 |
Spaced Identifiers
ISO 14977 allows spaces within rule names. For example, signed integer is treated as a single rule name, equivalent to signedinteger. This feature is off by default for compatibility with common EBNF usage.
To enable:
{
"ebnf.parser.spacedIdentifiers": true
}
EBNF Quick Reference
| Syntax |
Meaning |
= |
Definition |
; or . |
End of rule |
\| |
Alternative (or) |
, |
Concatenation (sequence) |
[ ... ] |
Optional (zero or one) |
{ ... } |
Repetition (zero or more) |
( ... ) |
Grouping |
"..." or '...' |
Terminal string |
(* ... *) |
Comment |
? ... ? |
Special sequence |
- |
Exception |
3 * rule |
Repetition (exactly 3 times) |
Development
bun run build # Build the extension
bun run package # Create .vsix package
License
MIT
Links
