clean-code

name	clean-code
description	Structural code quality rules applied at write time (implementer, scaffolder) and check time (reviewer). Covers function length, single responsibility, abstraction levels, meaningful naming, magic values, parameter design, boolean traps, DRY, dead code, premature abstraction, frontend component decomposition, null safety, async safety, input validation at boundaries, and concurrency safety.

Clean Code Skill

Structural quality rules for writing and reviewing code within the Archon plugin. These rules are cross-runtime principles with runtime-specific thresholds captured in tables within each sub-file.

What this skill covers

Rule ID	Name	Sub-file
CC-S1	Function length	structure.md
CC-S2	Single responsibility	structure.md
CC-S3	Abstraction levels	structure.md
CC-N1	Meaningful names	naming.md
CC-N2	Magic values	naming.md
CC-I1	Parameter count	interface.md
CC-I2	Boolean trap	interface.md
CC-H1	DRY	hygiene.md
CC-H2	Dead code	hygiene.md
CC-H3	Premature abstraction	hygiene.md
CC-F1	Component size	frontend.md
CC-F2	Props interface	frontend.md
CC-F3	Logic extraction	frontend.md
CC-NS1	No unguarded nullable access	null-safety.md
CC-NS2	No non-null assertion	null-safety.md
CC-NS3	Declare nullable return types	null-safety.md
CC-NS4	Guard collection access	null-safety.md
CC-NS5	Validate external data before use	null-safety.md
CC-NS6	Propagate null, do not swallow	null-safety.md
CC-AS1	Every promise must be awaited	async-safety.md
CC-AS2	Do not mix async styles	async-safety.md
CC-AS3	Async errors must propagate	async-safety.md
CC-AS4	No parallel state mutation	async-safety.md
CC-AS5	Timeout on all external async calls	async-safety.md
CC-IV1	Validate request body before use	input-validation.md
CC-IV2	Validate path and query params	input-validation.md
CC-IV3	Sanitise string inputs	input-validation.md
CC-IV4	Validate env vars at startup	input-validation.md
CC-IV5	Reject unknown fields	input-validation.md
CC-CS1	No mutable loop variable capture	concurrency-safety.md
CC-CS2	Correct React state update pattern	concurrency-safety.md
CC-CS3	Module-level singletons must be concurrency-safe	concurrency-safety.md
CC-CS4	No non-atomic paired reads	concurrency-safety.md
CC-CS5	Idempotency keys for state-mutating ops	concurrency-safety.md

What this skill does NOT cover

These concerns are owned by other skills/commands — do not duplicate:

• Logging patterns → skills/production-hardening/
• Error handling, retry, timeout → skills/production-hardening/
• Auth patterns → skills/production-hardening/
• Import style, naming case (camelCase vs snake_case) → pattern fingerprint
• Cyclomatic complexity scoring → /architect:complexity-check
• Security vulnerabilities → /architect:review Check 3, /architect:security-scan
• Architecture layer violations (logic in route, cross-component imports) → /architect:review Check 5

---

Severity Table

Rule	Severity	Rationale
CC-S1 function length	WARNING	Structure debt — not immediately broken
CC-S2 single responsibility	WARNING	Same class of issue as CC-S1
CC-S3 abstraction levels	SUGGEST	Subtle and context-dependent
CC-N1 meaningful names	WARNING	Generic names accumulate into readability debt across the codebase
CC-N2 magic values	WARNING	Unexplained literals create silent maintenance hazards
CC-I1 parameter count	WARNING	Design smell — signals a missing abstraction
CC-I2 boolean trap	SUGGEST	Unreadable at call site but logic is correct
CC-H1 DRY	SUGGEST at 2 occurrences / WARNING at 3+	Reviewer must count before assigning
CC-H2 dead code	WARNING	Misleads readers, pollutes git blame
CC-H3 premature abstraction	WARNING	Directly violates CLAUDE.md: "Don't create helpers for one-time operations"
CC-F1 component size	WARNING	Monolithic components block reuse and testing
CC-F2 props interface	WARNING	Over-coupled components indicate decomposition is needed
CC-F3 logic extraction	SUGGEST	Logic in render functions works but is harder to test
CC-NS1 unguarded nullable access	BLOCKER	Directly causes TypeError/AttributeError/nil pointer dereference in production
CC-NS2 non-null assertion	WARNING	Bypasses the type system — generated code must not use it
CC-NS3 undeclared nullable return	WARNING	Callers cannot write safe code against undeclared nullable returns
CC-NS4 unguarded collection access	BLOCKER	Index out of bounds / undefined on empty collections crashes in production
CC-NS5 unvalidated external data	BLOCKER	Malformed external data causes crashes or silent data corruption
CC-NS6 null swallowed in service	WARNING	Hides absence from caller — leads to wrong-data bugs

BLOCKERs in this skill: CC-NS1, CC-NS4, CC-NS5, CC-AS1, CC-AS3, CC-IV1, CC-IV2, CC-CS1. These are safety rules that cause runtime crashes or silent failures — not style issues.

---

Implementer Read Protocol

Read SKILL.md (this file) once at the start of the write session to get the severity table and sub-file map. Then read only the sub-files relevant to the layer you are about to write.

Apply rules as design constraints during writing — not as post-hoc detectors. Fix before moving to the next function.

Layer	Sub-files to read	Key rules
Schema / validation	naming.md + interface.md + null-safety.md + input-validation.md	CC-N1, CC-N2, CC-I1, CC-NS3, CC-NS5, CC-IV3, CC-IV5
Service layer	structure.md + naming.md + interface.md + hygiene.md + null-safety.md + async-safety.md	All backend rules + all NS + AS rules
Route / controller	structure.md + interface.md + null-safety.md + input-validation.md	CC-S1, CC-S2, CC-I2, CC-NS1, CC-NS4, CC-IV1, CC-IV2, CC-IV3, CC-IV5
Integration lib	naming.md + hygiene.md + null-safety.md + async-safety.md	CC-N1, CC-H3, CC-NS1, CC-NS5, CC-AS1, CC-AS5
Test layer	hygiene.md	CC-H1, CC-H2
Frontend component	frontend.md + naming.md + null-safety.md + concurrency-safety.md	CC-F1, CC-F2, CC-F3, CC-N1, CC-NS1, CC-NS4, CC-CS1, CC-CS2
Config / startup	input-validation.md	CC-IV4

During writing — apply in this order:

1. Before writing a function signature: apply CC-I1 (parameter count), CC-N1 (naming), and CC-NS3 (declare nullable return type if the function can return null/undefined/None).
2. For route handlers: apply CC-IV1 and CC-IV2 — write the schema parse as the first statement before any field access.
3. After every call to a DB query, external API, or collection lookup: apply CC-NS1 (null guard) and CC-NS4 (collection guard) — place the guard immediately before any property access.
4. After every async function call: apply CC-AS1 — ensure await is present or the Promise is explicitly returned/handled.
5. After writing the function body: apply CC-S1 (length). Decompose before continuing if over threshold.
6. After writing a file: apply CC-H2 (dead code) and CC-H3 (premature abstraction).
7. When copying a logic block: apply CC-H1 (DRY) — extract before copying a second time.
8. For frontend files: apply CC-F1 (component size) before writing JSX return; apply CC-CS2 for any setState that depends on previous state.
9. For loop bodies with closures or goroutines: apply CC-CS1 — verify the loop variable is correctly bound.
10. Whenever consuming external data (API response, env var, IPC payload, DB row): apply CC-NS5 and CC-IV1 — validate shape before accessing fields.

---

Scaffolder Read Protocol

The scaffolder reads naming.md + hygiene.md + null-safety.md + async-safety.md + input-validation.md + concurrency-safety.md before generating any file.

Rule	Applies	Note
CC-N1 meaningful names	Yes	Template names become the codebase baseline
CC-N2 magic values	Yes	No hardcoded ports/timeouts/limits in generated files
CC-H2 dead code	Yes — critical	No TODOs, no commented-out blocks in generated scaffold files
CC-H3 premature abstraction	Yes — critical	Do not generate single-use utility wrappers
CC-S1 function length	Yes	Template functions should not be monolithic
CC-H1 DRY	Partial	3+ occurrences rule only — scaffold legitimately repeats patterns
CC-NS1 unguarded nullable access	Yes — critical	Every DB lookup/find-by-id must have a null guard before property access
CC-NS2 non-null assertion	Yes — banned	Never emit ! assertions or !! in generated code
CC-NS3 nullable return types	Yes — critical	Repository/service functions that can return null must declare it
CC-NS4 collection access guard	Yes — critical	Never generate items[0].x or .find().x without a prior guard
CC-NS5 validate external data	Yes — critical	Never emit bare (await res.json()) as T; always validate first
CC-NS6 propagate null	Yes	Service layer throws or returns typed null — not empty default objects
CC-AS1 await every promise	Yes — critical	Never generate a floating async call without await or explicit handling
CC-AS2 consistent async style	Yes	Never mix await and .then() chains in the same generated function
CC-AS3 propagate async errors	Yes — critical	No bare catch { return null } in service or integration layers
CC-AS5 timeout on external calls	Yes	Every generated HTTP/DB call stub must include a timeout
CC-IV1 validate request body

Rules that do NOT apply to scaffold: CC-S2, CC-S3, CC-I1, CC-I2, CC-F1, CC-F2, CC-F3, CC-AS4, CC-CS3, CC-CS4.

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Reviewer Reference Map

The reviewer reads SKILL.md first to determine which sub-files are relevant based on the diff content.

Reviewer check	Sub-files to read	Findings added
Check 1 — Pattern conformance	naming.md + hygiene.md + null-safety.md + async-safety.md + input-validation.md + concurrency-safety.md + interface.md (if new functions with many params)	All check IDs below
Check 4 — Test coverage	hygiene.md (CC-H2 only)	cleancode-dead-code
Check 5 — Architecture fitness	structure.md + frontend.md (if diff includes frontend files)	cleancode-fn-length, cleancode-single-responsibility, cleancode-abstraction-levels, cleancode-component-size, cleancode-props-interface, cleancode-logic-extraction

Check IDs (check field in findings result contract):

cleancode-fn-length
cleancode-single-responsibility
cleancode-abstraction-levels
cleancode-naming
cleancode-magic-value
cleancode-param-count
cleancode-boolean-trap
cleancode-dry
cleancode-dead-code
cleancode-premature-abstraction
cleancode-component-size
cleancode-props-interface
cleancode-logic-extraction
cleancode-null-unguarded
cleancode-null-assertion
cleancode-null-return-type
cleancode-null-collection
cleancode-null-external
cleancode-null-swallowed
cleancode-async-unawaited
cleancode-async-mixed-style
cleancode-async-error-swallowed
cleancode-async-parallel-mutation
cleancode-async-no-timeout
cleancode-iv-body-unvalidated
cleancode-iv-params-unvalidated
cleancode-iv-string-unsanitised
cleancode-iv-env-unvalidated
cleancode-iv-unknown-fields
cleancode-cs-loop-capture
cleancode-cs-stale-closure
cleancode-cs-shared-mutable
cleancode-cs-nonatomic-reads
cleancode-cs-nonidempotent