codeguard-scala

Scala Codeguard Gate

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

Start in 30 seconds

1. At the repository root, confirm that build.sbt or the target file exists.
2. Detect tools:scalafmt --version。
3. First do a read-only check:scalafmt --check .。
4. Classify results as: code violations, missing configuration, missing tools, tool internal errors.
5. Only perform safe fixes:scalafmt。
6. Rerun lint, and run the project's existing test/build gates.

Can be directly requested:

• "Check this Scala project, do not modify anything yet, and give me a classification of lint failures."
• "Only fix Scala formatting issues; list semantic issues first."
• "Verify Scala lint, test, and build evidence before committing."

Capability boundaries

✅ Good at handling

1. Based on .scala, .sc and project markers to identify the Scala workspace.
2. Run scalafmt --check . and retain the exit code, scope, and tool version.
3. Distinguish formatting, static rules, configuration, dependency, and environment failures.
4. Use scalafmt to handle reversible issues and rescan.
5. Report local results in layers with CI/build/test evidence.

⚠️ Requires conditions

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

❌ Not applicable

1. Do not treat formatter passing as compilation, test, or security audit passing.
2. Do not silently install tools, upgrade dependencies, or modify team rules.
3. Do not use suppress/ignore/raising thresholds to hide real problems.
4. Do not claim "checks passed" when tools or configuration are missing.

When to use

• The user requests checking or fixing Scala code style.
• AI modified .scala, .sc, and pre-commit verification is needed.
• CI shows failures related to scalafmt --check . .
• Need to determine whether an issue can be fixed automatically or must be handled manually.

When not to use

• When the main task is learning language syntax, framework design, or business modeling, use the corresponding language professional skill instead.
• When the main task is dependency vulnerabilities, security auditing, or license governance, use a dedicated security skill.
• When the user only asks to explain one error and there is no project context, first give a local explanation and do not claim the repository is all 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 changes must be explicitly confirmed by the user.

Execution Contract

Item	Current Fact
Status	stable(Since Codeguard V0.2)
File Extensions	.scala, .sc
Project Markers	build.sbt
Integration Configuration	.scalafmt.conf
Tool Readiness	coursier install scalafmt
Detection Commands	使用命令查找与项目配置检查
lint	scalafmt --check .
format/fix	scalafmt
Project-level gate	scalafmt --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 .scalafmt.conf and the actual commands in CI. Repository configuration takes precedence over the examples in this skill; if the two conflict, report the difference first.

Step 3: Detect Tools and Versions

Run 对应工具 --version. If a tool is missing, the version is incompatible, or the configuration cannot be loaded, record it as “Unable to verify,” not a pass.

Step 4: Run Read-Only Checks

Run scalafmt --check .and record 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 formatter, then check the diff
Static Rules	unused, complexity, naming, dangerous APIs	Minimal semantic fix; batch guessing is prohibited
Configuration	parser/config/schema not found	Fix the integration or report preconditions
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 scalafmt. 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. Only write “pass” 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. Evidence Layering: Report lint, format, compile, test, and security separately.
3. Minimal Changes: Do not refactor along the way, and do not expand a style fix into a business rewrite.
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

Scala 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 — must output UNVERIFIED and a clear preparation method.
2. A formatter is not a linter — all-green formatting cannot override static rules or compilation errors.
3. The root directory determines the result — Running in the wrong module may miss detections or load an incorrect configuration.
4. Placeholders are not literal arguments — {file} and must be replaced with real, authorized paths.
5. Auto-fixes may enlarge the diff — After fixing, review the diff first, then run the regression gate.
6. Generated and vendor directories require an explicit policy — Do not arbitrarily scan the whole repository or modify third-party content.

Domain Pitfalls and Fixes

1. Project configuration takes precedence — Tool defaults must not override rules and version constraints already committed in the repository.

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 tool and version;
3. Project configuration files;
4. The authoritative command in CI;
5. Whether auto-fixing is 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 comments be added automatically? No. Exemptions are allowed only when the user explicitly accepts them and the reason is recorded.

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; when there are no rules, exclude generated/vendor first, then explain to the user.

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

Q6: If it passes locally, can we say CI will pass? No. CI's versions, environment variables, operating system, and command scope still need to be aligned.

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 everything at once.