cc-defensive-programming
Applies Code Complete's defensive programming rules: barricade design, assertion vs error-handling selection, input validation policy, and correctness-vs-robustness strategy for the current context.
aposd-reviewing-module-design
Assesses existing module and interface design for complexity symptoms: information leakage, shallow interfaces, pass-through layers, and unknown unknowns. Produces a structured assessment — not transformations.
Full skill instructions
Run the checklist. The checklist exists because intuition misses structural problems.
Unknown unknowns are highest severity. If it's unclear what code/info is needed for changes, flag immediately.
Use this systematic checklist when reviewing code:
| Symptom | Question | If Yes |
|---|---|---|
| Change Amplification | Does a simple change require modifications in many places? | Flag dependency problem |
| Cognitive Load | Must developer know too much to work here? | Flag obscurity or leaky abstraction |
| Unknown Unknowns | Is it unclear what code/info is needed for changes? | Highest severity - flag immediately |
| Check | Deep (Good) | Shallow (Bad) |
|---|---|---|
| Interface vs implementation | Interface much simpler | Interface rivals implementation |
| Method count | Few, powerful methods | Many, limited methods |
| Hidden information | High | Low |
| Common case | Simple to use | Complex to use |
Red flag: If understanding the interface isn't much simpler than understanding the implementation, the module is shallow.
| Red Flag | Detection | Severity |
|---|---|---|
| Information Leakage | Same knowledge in multiple modules | High |
| Temporal Decomposition | Structure mirrors execution order rather than knowledge | Medium |
| Back-Door Leakage | Shared knowledge not visible in interfaces but both depend on it | High |
| Overexposure | Common use forces learning rare features | Medium |
| Silent Failure | Module swallows errors, returns defaults, or hides failure states from callers | High |
| Red Flag | Detection | Severity |
|---|---|---|
| Pass-Through Method | Method only passes arguments to another with same API | High |
| Adjacent Similar Abstractions | Following operation through layers, abstractions don't change | High |
| Shallow Decorator | Large boilerplate, small functionality gain | Medium |
Test: Follow a single operation through layers. Does the abstraction change with each method call? If not, there's a layer problem.
| Red Flag | Detection | Severity |
|---|---|---|
| Conjoined Methods | Can't understand one method without another's implementation | High |
| Special-General Mixture | General mechanism contains use-case specific code | High |
| Code Repetition | Same code appears in multiple places | Medium |
| Shallow Split | Method split resulted in interface ≈ implementation | Medium |
When evaluating whether code should be combined or separated:
1. Do pieces share information?
YES → Should probably be together
2. Would combining simplify the interface?
YES → Should probably be together
3. Is there repeated code?
YES → Extract shared method (if long snippet, simple signature)
4. Does module mix general-purpose with special-purpose?
YES → Should be separated
Key principle: Depth > Length. Never sacrifice depth for length.
| Situation | Correct Action |
|---|---|
| Long method with clean abstraction | Keep together |
| Short method requiring another's impl to understand | Combine them |
| Method split creating conjoined pair | Undo the split |
| Long method with extractable subtask | Extract subtask only |
Test for valid split: Can the pieces be understood independently AND reused separately?
When reporting findings, use:
## Design Review: [Component Name]
### Critical Issues (Must Address)
- [Red flag]: [Specific location] - [Why it's a problem]
### Moderate Issues (Should Address)
- [Red flag]: [Specific location] - [Why it's a problem]
### Observations (Consider)
- [Pattern noticed] - [Potential concern]
### Positive Patterns
- [What's working well]
Before reporting any red flag, validate:
Ask before concluding:
| Question | If Yes |
|---|---|
| Is there an existing pattern for this type of problem? | Compare approaches |
| Does this introduce a second way to do the same thing? | Flag unless justified |
| Would a maintainer be surprised by the difference? | Requires explicit documentation |
Balance: Evaluate patterns on merit, but don't create gratuitous inconsistency. The goal is maintainability, not conformance.
| Conflict | Resolution |
|---|---|
| Depth vs Cohesion | Prefer cohesion. A focused shallow module beats a bloated deep one. |
| Information Hiding vs Testability | Testing seams (injectable dependencies) are acceptable "leakage" |
| Simple Interface vs Configurability | Real systems need configuration; penalize only unnecessary complexity |
Detailed per-dimension checklists: Read(${CLAUDE_SKILL_DIR}/checklists.md)
| After | Next |
|---|---|
| Issues found, transformation needed | Read(${CLAUDE_PLUGIN_ROOT}/skills/aposd-simplifying-complexity/SKILL.md) (transformation vs assessment) |
| Issues found, plan needed | Flag for /code-foundations:plan |
| No issues | Done |
Applies Code Complete's defensive programming rules: barricade design, assertion vs error-handling selection, input validation policy, and correctness-vs-robustness strategy for the current context.
Structures routine design through pseudocode-first iteration: clarifies naming and purpose before any code, catches design flaws cheaply, and prevents compile-debug loops on poorly understood routines.
Transforms complex code by applying APOSD's pull-complexity-downward principle: resolves error hierarchies, collapses configuration, and moves caller-side logic into modules. Produces edited code, not just assessment.
Guides safe refactoring using Code Complete's fix-first-then-refactor discipline: decides between refactor, rewrite, and fix-first; enforces separate commits; applies small-change rigor to high-error-rate one-liners.
Guides module and API design using APOSD principles: generates multiple design alternatives, compares them on information hiding and interface depth, and produces a documented design decision.
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