vscode-bnf-intellisense
Edit ABNF, BNF, W3C XML EBNF, and RBNF files in VS Code with highlighting,
navigation, diagnostics, formatting, snippets, and rule-aware completions.
Fast Path
Use the extension:
- Install the extension.
- Open an
.abnf, .bnf, .ebnf, or .rbnf file.
- Check the VS Code language mode if highlighting or diagnostics do not appear.
Work on the extension:
bun install
bun run build
Check changes before a PR:
bun run biome:check
bun run typecheck
bun test
bun run build
Build a local VSIX:
bun run package
Supported Grammars
| File |
Language |
Standard |
Supported syntax |
.abnf |
ABNF |
RFC 5234 + RFC 7405 |
Rule names, =, =/, /, repetitions, numeric values, prose values, and %s/%i strings. |
.bnf |
BNF |
W3C BNF notation |
::= productions, alternatives, grouping, optional parts, repetitions, and literals. |
.ebnf |
EBNF |
W3C XML 1.0 EBNF notation |
Production numbers, ::=, ?, +, *, character classes, character exclusions, and /* */ comments. |
.rbnf |
RBNF |
RFC 5511 |
::= productions and angle-bracket rule names, including names with spaces. |
ISO/IEC 14977 EBNF is not supported. .ebnf files use W3C XML EBNF. ISO-style
= productions are reported as diagnostics.
Editor Features
- TextMate highlighting for grammar files and Markdown code fences.
- Semantic highlighting for full rule names and references.
- Go to Definition, Find References, Rename, Hover, Document Symbols, and
Workspace Symbols.
- Diagnostics for missing definitions, duplicate definitions, unused rules,
empty rule bodies, and dialect-specific syntax mistakes.
- Formatting for aligned assignments, wrapped alternatives, final newlines, and
comment spacing.
- Inlay hints for reference counts, direct recursion, unused rules, repetitions,
terminals, and character classes.
- Snippets for common grammar constructs.
RBNF names such as <WF flow descriptor> stay one symbol. Rename, references,
and highlighting keep the full angle-bracket name together.
Examples
Equivalent JSON grammars:
ABNF:
json-text = ws value ws
value = object / array / string / number / true / false / null
object = begin-object ws [member *(ws value-separator ws member)] ws end-object
W3C BNF:
<json-text> ::= <ws> <value> <ws>
<value> ::= <object> | <array> | <string> | <number> | "true" | "false" | "null"
<object> ::= "{" <ws> [<member> {<ws> "," <ws> <member>}] <ws> "}"
W3C XML EBNF:
[1] json-text ::= ws value ws
[2] value ::= object | array | string | number | "true" | "false" | "null"
[3] object ::= "{" ws (member (ws "," ws member)*)? ws "}"
RBNF:
<JSON text> ::= <WS> <value> <WS>
<value> ::= <object> | <array> | <string> | <number> | "true" | "false" | "null"
<object> ::= "{" <WS> [<member> *(<WS> "," <WS> <member>)] <WS> "}"
Settings
All settings use the bnf.* prefix.
| Setting |
Default |
Effect |
bnf.diagnostics.enable |
true |
Shows parser and rule diagnostics. |
bnf.diagnostics.unusedRules |
true |
Shows hints for rules with no references. |
bnf.diagnostics.undefinedReferences |
true |
Shows errors for references with no rule definition. |
bnf.formatting.alignEquals |
true |
Aligns assignment operators across consecutive rules. |
bnf.formatting.continuationIndent |
4 |
Sets spaces for wrapped rule-body lines. |
bnf.formatting.alternativeIndent |
align |
Uses align or indent for alternatives on continuation lines. |
bnf.formatting.blankLinesBetweenRules |
1 |
Keeps this many blank lines between rule definitions. |
bnf.formatting.breakAlternatives |
always |
Uses always, auto, or never for top-level alternatives. |
bnf.formatting.maxLineLength |
80 |
Wraps rule bodies after this column. Use 0 to disable wrapping. |
bnf.formatting.alignProductionNumbers |
true |
Aligns EBNF production numbers such as [1]. |
bnf.formatting.preserveCommentSpacing |
true |
Keeps blank-line spacing around standalone comments. |
bnf.formatting.trimTrailingBlankLines |
true |
Removes extra blank lines at the end of the file. |
bnf.formatting.preserveContinuationLineBreaks |
false |
Keeps existing indented continuation line breaks. |
bnf.formatting.spaceBeforeInlineComment |
2 |
Sets spaces before inline semicolon comments in rule bodies. |
bnf.formatting.insertFinalNewline |
true |
Ends formatted files with one final newline. |
bnf.inlayHints.referenceCount |
false |
Shows reference counts after rule names. |
bnf.inlayHints.recursion |
false |
Marks rules that reference themselves directly. |
bnf.inlayHints.unusedMarker |
false |
Marks rules with no references. |
bnf.inlayHints.syntaxDetails |
false |
Shows syntax hints for repetitions, terminals, and character classes. |
bnf.semanticHighlighting.mode |
auto |
Uses auto, on, or off for semantic tokens. |
bnf.semanticHighlighting.maxTokens |
20000 |
Sets the semantic-token limit in auto mode. Use 0 for no limit. |
If Something Looks Wrong
- No highlighting: set the VS Code language mode to
ABNF, BNF, EBNF, or
RBNF.
- No diagnostics: check
bnf.diagnostics.enable.
- Missing-rule errors feel noisy: set
bnf.diagnostics.undefinedReferences to
false.
- Large files feel slow: set
bnf.semanticHighlighting.mode to off, or lower
bnf.semanticHighlighting.maxTokens.
- Formatter changes too much: adjust
bnf.formatting.* settings, then format a
small selection before formatting the full file.
Maintainers And Agents
Star History
Star History
License
MIT
| |
