codeguard-fsharp

F# Codeguard Gate

Goal: turn "looks fine" into repeatable tool evidence, and honestly distinguish pass, fail, unable to verify, and planned.

30-second start

1. At the repository root, confirm 无专用标记文件 or the target file exists.
2. Probe the tool:dotnet --version。
3. Read-only check first:dotnet fantomas --check。
4. Classify results as: code violations, missing configuration, missing tooling, tool internal errors.
5. Only perform on safely fixable items:dotnet fantomas。
6. Re-run lint, and run the project's existing test/build gates.

Can be proposed directly:

• "Check this F# project, don't modify anything yet, give me a classification of lint failures."
• "Only fix F# formatting issues, list semantic issues first."
• "Verify F# lint, test, and build evidence before committing."

Capability boundaries

✅ Good at handling

1. Based on .fs, .fsi, .fsx and project markers to identify F# workspaces.
2. Execute dotnet fantomas --check and retain exit codes, scope, and tool versions.
3. Distinguish formatting, static rules, configuration, dependency, and environment class failures.
4. Use dotnet fantomas to handle reversible issues and rescan.
5. Report local results layered with CI/build/test evidence.

⚠️ Requires conditions

1. The target tool must be installed and its version compatible with project constraints.
2. Must be executed from the correct repository or module root directory.
3. If the project has custom configuration, the committed configuration takes precedence.
4. Whether generated code, vendor, and cache directories are scanned must follow repository rules.

❌ Not applicable

1. Do not treat formatter pass as compile, test, or security audit pass.
2. Do not silently install tools, upgrade dependencies, or modify team rules.
3. Do not use suppress/ignore/raising thresholds to mask real issues.
4. Do not claim "check passed" when tooling or configuration is missing.

When to use

• The user requests checking or fixing F# code style.
• AI modified .fs, .fsi, .fsx, requiring pre-commit verification.
• CI shows failures related to dotnet fantomas --check .
• Need to determine whether an issue can be auto-fixed or must be handled manually.

When not to use

• The primary task is learning language syntax, framework design, or business modeling, in which case the corresponding language professional skill should be used instead.
• The primary task is dependency vulnerabilities, security audit, or license governance, in which case a dedicated security skill should be used.
• When the user only asks to explain an error and there is no project context, provide a local explanation first, and do not claim the whole repository is green.

Data and security

This skill does not collect, upload, send, or store user code and credentials. By default it only reads local repository configuration and runs local tools; it does not install dependencies over the network, and does not record tokens, passwords, or private source code. Before any automatic fix, check the diff first; destructive or large-scale modifications must be explicitly confirmed by the user.

Execution contract

Project	Current facts
Status	stable(since Codeguard V0.5)
File extensions	.fs, .fsi, .fsx
Project markers	No dedicated marker files
Integration configuration	Follow the repository's existing configuration
Tool preparation	dotnet tool install -g fantomas
Detection commands	使用命令查找与项目配置检查
lint	dotnet fantomas --check
format/fix	dotnet fantomas
Project-level gate	dotnet fantomas --check

Standard Workflow

Step 1: Determine the real scope

Confirm the repository root, module roots, generated directories, vendor directories, and user-specified files. For multi-module projects, first list the modules that will be scanned; do not guess based on the current directory.

Step 2: Read the project contract

Read the actual commands in Follow the repository's existing configuration and CI. Repository configuration takes precedence over the examples in this skill; if the two conflict, report the differences first.

Step 3: Detect tools and versions

Run 对应工具 --version. A missing tool, an incompatible version, or a configuration that cannot be loaded is recorded as "unable to verify", not as a pass.

Step 4: Perform read-only checks

Run dotnet fantomas --check, recording the command, working directory, exit code, tool version, and the first actionable error.

Step 5: Failure classification

Type	Typical signal	Handling
Formatting	Indentation, whitespace, import order	Allow the formatter, then check the diff
Static rules	unused, complexity, naming, dangerous APIs	Minimal semantic fixes; no bulk guesswork
Configuration	parser/config/schema not found	Fix the integration or report prerequisites
Environment	command not found, version conflict	Report installation/version requirements; do not install silently
Tool internal error	crash, timeout, parser exception	Preserve the original evidence and narrow the reproduction scope

Step 6: Controlled fixes

Prefer to run dotnet fantomas. Only handle issues that are certain and reversible; dependency upgrades, rule exemptions, generated files, and business semantic changes must be explained separately.

Step 7: Verification loop

Re-run the same lint command, then run the project's existing tests and build. Write "pass" only when the command, scope, and exit code are all clear; otherwise write "not run" or "unable to verify".

Rules

1. Re-verify with the same command: after fixing, you must re-run the original command that triggered the failure.
2. Layered evidence: report lint, format, compile, test, and security separately.
3. Minimal changes: do not refactor along the way, and do not expand style fixes into business rewrites.
4. Configuration first: do not override the project's existing ignore, dialect, target, or version constraints.
5. No fabrication: tools not run, configurations not seen, and platforms not verified must be clearly marked.

Output template

F# Codeguard 结果
- 范围：<仓库/模块/文件>
- 工具：<名称与版本>
- 命令：<实际命令>
- 状态：PASS / FAIL / UNVERIFIED / PLANNED
- 发现：<按格式/规则/配置/环境分类>
- 修改：<文件与原因；无修改写 none>
- 复验：<命令、退出码>
- 未验证：<测试/构建/平台差异>

Gotchas

1. A missing tool is not a pass — it must output UNVERIFIED and a clear preparation method.
2. A formatter is not a linter — all-green formatting cannot cover static rules or compilation errors.
3. The root directory determines the result — running in the wrong module may miss issues or load the wrong configuration.
4. Placeholders are not literal arguments — {file} must be replaced with real, authorized paths.
5. Automatic fixes may expand the diff — after fixing, review the diff first, then run the regression gate.
6. Generated and vendor directories need an explicit policy — do not casually scan or modify third-party content across the whole repository.

Domain pitfalls and fixes

1. Domain pitfalls — Fantomas mainly handles formatting and does not replace the compiler, tests, and analyzers.

When information is insufficient

Do not just say "please provide more information." First give a safe read-only inspection plan, and list the specific items that still need confirmation:

1. repository/module root directory;
2. target tools and versions;
3. project configuration files;
4. the authoritative commands in CI;
5. whether automatic fixes are allowed.

FAQ

Q1: If the tool is not installed, can we conclude the code is fine? No. The status must be UNVERIFIED。

Q2: Can ignore or suppression be added automatically? No. Exemptions are allowed only when the user explicitly accepts them and the reason is documented.

Q3: Why does it still fail after formatting? The formatter only covers formatting; static rules, configuration, compilation, and tests still need to be handled separately.

Q4: Should generated code be scanned? By default, follow the repository configuration; if there are no rules, exclude generated/vendor first, then explain to the user.

Q5: How can I avoid changing too much at once? Fix in batches by failure category and file first, and rerun the original command and review the diff after each batch.

Q6: If it passes locally, can I say CI will pass? No. You also need to align with CI's versions, environment variables, operating system, and command scope.

Load resources on demand

• When encountering exit codes, failure classification, or exemption decisions, read references/rules/gate-rules.md。
• When you need to verify this language's registry, toolchain, and project configuration, read references/tooling/toolchain.md。
• When you need copyable task examples, read by scenario examples/, and there is no need to load all of them at once.