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syntax-definition

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Create or update a Sublime Text 3 compatible `.sublime-syntax` grammar in the repository `syntaxes/` directory when asked for a specific language or format such as JSON, TypeScript, Elm, or Dockerfile.

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Source SKILL.md: https://github.com/jmacdonald/amp/blob/HEAD/.agents/skills/syntax-definition/SKILL.md

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Syntax Definition

Use this skill when asked to create or update a syntax definition for a named language or file format.

Goal

Create or update exactly one grammar file in the repository top-level syntaxes/ directory:

  • syntaxes/<Language>.sublime-syntax

Also create or update one fixture/expectations pair under tests/fixtures/syntaxes/<language>/:

  • <sample>.<ext>
  • <sample>.<ext>.tokens.yml

Examples:

  • JSON -> syntaxes/JSON.sublime-syntax
  • TypeScript -> syntaxes/TypeScript.sublime-syntax
  • Elm -> syntaxes/Elm.sublime-syntax
  • Dockerfile -> syntaxes/Dockerfile.sublime-syntax

If a matching file already exists, update it instead of creating a duplicate.

Required Constraints

  • Only produce Sublime Text 3 compatible grammars.
  • Do not use Sublime Text 4+ only syntax features.
  • Keep the file as YAML with the usual .sublime-syntax structure.
  • Do not write the grammar anywhere except the top-level syntaxes/ directory unless the user explicitly asks for something else.
  • Keep syntax regression fixtures under tests/fixtures/syntaxes/.

When compatibility is uncertain, prefer conservative syntax features:

  • %YAML 1.2
  • name
  • file_extensions
  • scope
  • variables
  • contexts
  • match
  • captures
  • scope
  • push
  • set
  • pop
  • include
  • meta_scope
  • meta_content_scope

Workflow

  1. Identify the requested language or format name.
  2. Inspect nearby files in syntaxes/ to match the repository's existing style and naming conventions.
  3. Create a practical first-pass grammar with the core building blocks for that language:
    • comments
    • strings
    • numbers
    • keywords
    • operators or punctuation
    • identifiers
  4. Add one representative sample file under tests/fixtures/syntaxes/<language>/.
  5. Add a YAML expectations file named <sample>.<ext>.tokens.yml with:
    • buffer_path: the virtual filename used to select the syntax
    • expectations: an ordered list of critical (text, scope) checks
  6. Run cargo test syntaxes to test and fix issues with the generated/updated syntax.

Output guidelines

For generated/updated syntaxes

  • Use a stable top-level scope such as source.<language> or text.<format> as appropriate.
  • Keep contexts readable and modular rather than over-optimizing the grammar.
  • If the language details are incomplete, make the smallest reasonable set of assumptions and state them briefly.
  • The resulting syntax file should be directly usable by the repository's syntax-loading code.
  • Prefer correctness and compatibility over advanced grammar tricks.

For syntax fixtures

  • Use critical-scope expectations only; do not snapshot every token unless the user explicitly asks for exhaustive coverage.
  • The fixture should be directly usable by the repository's scribe::Workspace.current_buffer_tokens() test harness.