code-antipatterns
Skill0 starsChanged 9 months agoMITView on GitHub
Antipattern catalog with categorized patterns, symptoms, examples, and fixes. Use when reviewing code for quality issues, detecting bad patterns during plan-audit or scope, evaluating whether a pattern is an antipattern or acceptable tradeoff, or fixing existing code smells. Covers surprise, misuse, complexity, and premature antipattern categories with severity classification.
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- code-namingSkill
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Code Antipatterns
Top 10 Code Antipatterns
| # | Antipattern | Category | Severity | One-Line Summary |
| 1 | Silent Failure | Surprise | Critical | Swallowing errors hides bugs until production |
| 2 | Mutable Shared State | Misuse | Critical | Shared mutation causes race conditions and data corruption |
| 3 | Primitive Obsession | Misuse | Warning | Using String where EmailAddress would prevent invalid data |
| 4 | Magic Values | Surprise | Warning | Unexplained literals obscure intent and invite inconsistency |
| 5 | God Object | Complexity | Warning | One class that knows and does everything |
| 6 | Premature Abstraction | Premature | Warning | Interfaces and factories before the second use case exists |
| 7 | Leaky Abstraction | Complexity | Warning | Callers must understand implementation details to use the API |
| 8 | Shotgun Surgery | Complexity | Warning | One logical change touches many files |
| 9 | Premature Optimization | Premature | Warning | Optimizing without profiling first |
| 10 | Cargo Cult Code | Premature | Note | Copying patterns without understanding why they exist |
Severity Classification
| Severity | Meaning | Action | Examples |
| Critical | Active risk of data loss, security breach, or production failure | Fix immediately | Silent failure, mutable shared state |
| Warning | Ongoing cost in maintainability, reliability, or team velocity | Fix soon or create a ticket | God object, primitive obsession, magic values |
| Note | Code smell that may not warrant immediate action | Consider during refactoring | Cargo cult code, lava flow, boolean blindness |
Antipattern or Acceptable Tradeoff?
| Signal | Antipattern | Acceptable Tradeoff |
| Duplicate code in two places | Wait — under threshold | Fix if three or more occurrences |
| Function takes a boolean param | Antipattern if unclear at call site | Acceptable if only one boolean and meaning is obvious |
| No interface for a dependency | Fine — add when second impl arrives | Antipattern if you need it for testing now |
| Global mutable state | Almost always an antipattern | Acceptable for true singletons (logger, config) with thread safety |
| Magic number | Antipattern if meaning is unclear | Acceptable for universally known values (0, 1, 100%) |
| Complex optimization | Antipattern without profiling evidence | Acceptable in measured hot paths with benchmarks |
| Dead code / commented blocks | Antipattern — delete it | Acceptable as temporary scaffold during active development |
| God object | Antipattern in production code | Acceptable in prototypes and spikes (plan to refactor) |
Context-Dependent Evaluation
| Context | Lean Toward | Rationale |
| Prototype / spike | Tolerance — focus on validation | You'll rewrite anyway |
| Shared library / public API | Strict — fix misuse and surprise patterns | Consumers can't easily work around your mistakes |
| Hot path (measured) | Allow optimization complexity | Performance justifies readability tradeoff |
| Security boundary | Strict on all categories | Security antipatterns compound |
| Greenfield project | Moderate — invest in structure early | Foundation decisions compound over time |
| Legacy codebase | Prioritize critical severity only | Don't boil the ocean; fix what matters |
Code Review Antipattern Scan
- No silent failures — errors either propagate or are explicitly handled
- No magic values — all non-obvious literals are named constants
- No unexpected side effects — query functions don't modify state
- No mutable shared state without explicit thread safety
- No primitive obsession — domain values have domain types where appropriate
- No god objects — each class has a single clear responsibility
- No premature abstraction — interfaces have or will soon have multiple implementations
- No shotgun surgery — related logic is centralized
"Should I Fix This Now?"
| Situation | Action |
| Critical severity in production code | Fix now |
| Warning severity blocking current task | Fix now |
| Warning severity in adjacent code | Create a ticket |
| Note severity | Consider during next refactoring pass |
| Any severity in prototype/spike code | Note for later — don't gold-plate throwaway work |
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