notjack.space
AI agent skill files related to programming with Racket
Add Resyntax skill
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resyntax/SKILL.md
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resyntax/SKILL.md
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---
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name: resyntax
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description: "Use this skill whenever running Resyntax to analyze or refactor Racket code. Triggers include: any mention of 'resyntax', 'refactoring' in a Racket context, requests to find idiomatic improvements in Racket code, or requests to clean up or modernize Racket code. Also use when the user asks to run linting or style checks on Racket files."
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---
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# Resyntax
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## Overview
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Resyntax is a refactoring tool for Racket. It analyzes Racket code and suggests
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idiomatic improvements, powered by `syntax-parse`-based refactoring rules. Use
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it to find and automatically apply refactorings such as removing legacy API
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calls, simplifying expressions, and modernizing code style.
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Resyntax has two modes: **analyze** (report suggestions) and **fix** (apply
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changes to files directly).
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---
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## Running Resyntax
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Resyntax is a *launcher*, not a `raco` command. Run it as `resyntax`, NOT
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`raco resyntax`.
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```sh
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# Analyze a single file (report suggestions without modifying anything)
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resyntax analyze --file path/to/file.rkt
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# Analyze all files in a directory
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resyntax analyze --directory path/to/project/
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# Analyze an installed package
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resyntax analyze --package my-package
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# Analyze only files changed relative to a Git branch
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resyntax analyze --local-git-repository . origin/main
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```
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### Applying fixes
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Use `resyntax fix` to apply suggested changes directly to files. **Always prefer
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`resyntax fix` over manually reproducing suggestions.** This ensures changes are
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exactly what Resyntax intended and makes auditing easier.
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```sh
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# Fix a single file
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resyntax fix --file path/to/file.rkt
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# Fix all files in a directory
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resyntax fix --directory path/to/project/
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# Fix an installed package
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resyntax fix --package my-package
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# Fix only files changed relative to a Git branch
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resyntax fix --local-git-repository . origin/main
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```
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---
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## Workflow: Using Resyntax to refactor code
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Follow this workflow when using Resyntax to improve code quality:
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### Step 1: Analyze to find suggestions
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Run `resyntax analyze` first to see what Resyntax would change, without
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modifying any files. Review the output to understand the suggestions.
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```sh
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resyntax analyze --file path/to/file.rkt
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```
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Output looks like:
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```
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resyntax: path/to/file.rkt:43:5 [rule-name]
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Description of the suggested change.
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43 (original-code ...)
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43 (suggested-replacement ...)
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```
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Each suggestion includes:
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- The file, line, and column
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- The rule name in brackets (e.g. `[syntax-protect-migration]`)
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- A description of why the change is suggested
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- The original code and the replacement
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### Step 2: Apply fixes with `resyntax fix`
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Once you've reviewed the suggestions and they look appropriate, use
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`resyntax fix` to apply them:
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```sh
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resyntax fix --file path/to/file.rkt
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```
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Resyntax modifies files in place. It may run multiple passes, since applying one
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fix can unlock further fixes.
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### Step 3: Run tests to verify
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Always run the project's tests after applying fixes:
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```sh
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raco test path/to/file.rkt
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```
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### Step 4: Review the diff
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Check what Resyntax actually changed:
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```sh
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git diff
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```
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This lets you (and reviewers) confirm the changes are correct before committing.
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---
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## Useful options
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### Limiting scope
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```sh
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# Apply at most N fixes
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resyntax fix --file foo.rkt --max-fixes 5
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# Modify at most N files
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resyntax fix --directory src/ --max-modified-files 3
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# Modify at most N lines total
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resyntax fix --directory src/ --max-modified-lines 50
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```
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### Targeting specific rules
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```sh
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# Only analyze with a specific refactoring rule
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resyntax analyze --file foo.rkt --refactoring-rule if-else-false-to-and
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# Only fix with a specific refactoring rule
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resyntax fix --file foo.rkt --refactoring-rule syntax-protect-migration
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```
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### Timeouts
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The default analyzer timeout is 10 seconds per analyzer per file. Increase it
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for files that are slow to expand:
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```sh
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resyntax analyze --file foo.rkt --analyzer-timeout 30000
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```
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### Git integration
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The `--local-git-repository` option is useful for analyzing only files that have
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been modified in a branch:
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```sh
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resyntax analyze --local-git-repository /path/to/repo origin/main
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```
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### Output formats for `resyntax fix`
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```sh
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# Output a commit message summarizing fixes to stdout
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resyntax fix --file foo.rkt --output-as-commit-message
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# Output results as JSON
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resyntax fix --file foo.rkt --output-as-json
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# Create individual Git commits for each fix
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resyntax fix --directory src/ --create-multiple-commits
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```
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---
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## Important: always use `resyntax fix`, not manual edits
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When applying Resyntax suggestions, **always use `resyntax fix`** to apply
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changes rather than manually editing files to match the suggestion output. This
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is important because:
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1. It guarantees the applied change exactly matches what Resyntax computed.
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2. It eliminates the risk of introducing typos or subtle differences when
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reproducing suggestions by hand.
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3. It makes code review easier — reviewers can trust that the diff came from the
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tool itself.
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The only reason to manually edit would be if `resyntax fix` fails on a specific
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file (e.g., due to expansion errors) but `resyntax analyze` was able to show the
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suggestion. In that case, note in the commit message that the change was applied
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manually based on a Resyntax suggestion.