// Use when code is too complex, has scattered error handling, configuration explosion, or callers doing module work. Triggers on: too complex, simplify, scattered errors, configuration proliferation, verbose error handling
Use when designing modules, APIs, or classes before implementation.
Use when reviewing code, assessing interfaces, during PR review, or evaluating 'is this too complex?' Triggers on: code review, design review, module complexity, interface assessment, PR review, structural analysis.
Use after implementing code. Triggers on: is it done, ready to commit, verify correctness, did I miss anything, pre-commit check.
Use when code has deep nesting (3+ levels), complex conditionals, loop design questions, high cyclomatic complexity (McCabe >10), or callback hell. Symptoms: arrow-shaped code, repeated conditions, confusing loop exits, lengthy if-else chains
Use when auditing defensive code, designing barricades, choosing assertion vs error handling, or deciding correctness vs robustness strategy. Triggers on: empty catch blocks, missing input validation, assertions with side effects, wrong exception abstraction level, garbage in garbage out mentality, deadline pressure to skip validation, trusted source rationalization.
Use when designing routines, stuck on where to start coding, caught in compile-debug loops, or code works but you don't understand why. Triggers on: starting a new coding task
| name | aposd-simplifying-complexity |
| description | Use when code is too complex, has scattered error handling, configuration explosion, or callers doing module work. Triggers on: too complex, simplify, scattered errors, configuration proliferation, verbose error handling |
Walk through each level of hierarchy for EACH error condition. The best way to deal with exceptions is to define errors out of existence.
Priority order: Define out → Mask → Aggregate → Crash (app-level only)
Do NOT present simplified code until the Transformation Checklist is complete.
Before adding complexity to an interface (new parameters, new exceptions, new caller responsibilities):
1. Is this complexity closely related to the module's existing functionality?
NO → Should it be pulled into a DIFFERENT module?
YES → Identify correct module, pull there
NO → Leave in place (may be inherent to caller's domain)
YES → Continue
2. Will pulling down simplify code elsewhere in the application?
NO → Do not pull down (no benefit)
YES → Continue
3. Will pulling down simplify the module's interface?
NO → Do not pull down (risk of leakage)
YES → Pull complexity down
All three conditions must be YES to pull down.
Critical Constraint: Pulling down UNRELATED complexity creates information leakage. If the complexity isn't intrinsic to the module's core abstraction, it doesn't belong there—find the right home or leave it with the caller.
| Situation | Wrong Approach | Right Approach |
|---|---|---|
| Uncertain what value to use | Export parameter | Compute automatically |
| Different contexts need different values | Export parameter | Use reasonable default, expose only for exceptions |
| Policy decision unclear | Let user decide | Make a decision and own it |
Configuration parameters represent incomplete solutions. Every parameter pushes complexity to every user/administrator. Prefer dynamic computation over static configuration.
Apply in order of preference:
| Priority | Technique | How It Works | Example |
|---|---|---|---|
| 1 | Define out | Change semantics so error is impossible | unset(x) = "ensure x doesn't exist" (not "delete existing x") |
| 2 | Mask | Handle at low level, hide from callers | TCP retransmits lost packets internally |
| 3 | Aggregate | Single handler for multiple exceptions | One catch block in dispatcher handles all NoSuchParameter |
| Special | Crash | Print diagnostic and abort (app-level only) | malloc failure in non-recoverable contexts |
Note on "Crash": This is NOT level 4 of a hierarchy—it's a special case for truly unrecoverable errors in application code. Libraries should NEVER crash; they expose errors for callers to decide.
When facing an exception handling decision:
1. Can semantics be redefined to eliminate the error condition?
YES → Define out of existence
NO → Continue
2. Can exception be handled at low level without exposing?
YES → Mask
NO → Continue
3. Can multiple exceptions share the same handling?
YES → Aggregate
NO → Continue
4. Is error rare, unrecoverable, and non-value-critical?
YES → Just crash (app-level only)
NO → Must expose (exception information needed outside module)
| Exception Case | Why | What to Do Instead |
|---|---|---|
| Security-critical errors | Aggregating auth errors loses security-relevant distinctions | Keep distinct types for audit/logging |
| Retry-differentiated errors | Callers need different retry strategies per error type | Expose type info for retry decisions |
| Silent data loss risk | Define-out can mask user errors, complicate debugging | Fail fast for essential data errors |
| Library code | Callers should decide crash policy, not library | Expose errors; let app-level code crash |
| Technique | Gate Question |
|---|---|
| Define out | Does anyone NEED to detect this error case? |
| Mask | Does the caller have ANY useful response to this error? |
| Aggregate | Do callers handle these errors identically? |
| Crash | Is this (a) application-level code, (b) truly unrecoverable, AND (c) crash acceptable? |
Before defining an error out of existence, verify it's an incidental error (safe) not an essential error (must fail fast):
| Question | If YES → | If NO → |
|---|---|---|
| Would this state occur in normal, correct operation? | Safe to define out | Fail fast |
| Can the caller proceed meaningfully with the "defined out" state? | Safe | Expose error |
| Does the user/system have another way to detect this condition if needed? | Safe | Consider exposing |
| Technique | How | When to Use |
|---|---|---|
| Reduce information needed | Abstraction, eliminate special cases | Design-level changes |
| Leverage reader knowledge | Follow conventions, meet expectations | Incremental improvements |
| Present explicitly | Good names, strategic comments | When other techniques insufficient |
If a code reviewer says your code is not obvious, it is not obvious—regardless of how clear it seems to you.
| Problem | Why Nonobvious | Fix |
|---|---|---|
| Generic containers (Pair, Tuple) | getKey() obscures meaning | Define specific class with named fields |
| Event-driven handlers | Control flow hidden | Document invocation context |
| Type mismatches | List declared, ArrayList allocated | Match declaration to allocation |
| Violated expectations | Code doesn't do what reader assumes | Document or refactor to meet expectations |
Before presenting simplified code, output a technique analysis table:
| Error Condition | Technique | Gate Check | Reasoning |
|-----------------|-----------|------------|-----------|
| [each error] | [1-4] | [PASS/FAIL]| [why] |
This prevents claiming hierarchy application without evidence.
Do NOT present simplified code until ALL boxes are checked:
| Conflict | Resolution Heuristic |
|---|---|
| Define Out vs Fail Fast | Define out for incidental errors. Fail fast for essential errors. |
| Mask vs Explicit Handling | Mask when caller has no useful response. Expose when caller's response differs. |
| Aggregate vs Specific Messages | Aggregate the HANDLING, preserve specificity in the MESSAGE. |
| Pull Down vs Single Responsibility | Only pull down complexity RELATED to module's core purpose. |
| Obviousness vs Brevity | When define-out creates non-obvious behavior, add explanatory comment. |
| Simplify vs Performance | Prefer simplicity unless profiling proves performance-critical. |
| Red Flag | Symptom | Transformation |
|---|---|---|
| Scattered exceptions | Same error handled in many places | Aggregate to single handler |
| Configuration explosion | Many parameters exported | Compute automatically, provide defaults |
| Caller doing module's work | Logic outside that belongs inside | Pull complexity down |
| Over-defensive code | Checks for impossible conditions | Define errors out |
| Generic containers | Pair<X,Y> obscures meaning | Create named structure |
| Comment-dependent understanding | Code unreadable without comments | Refactor for obviousness |
SIMPLIFICATION PRIORITY ORDER:
1. Can I ELIMINATE this complexity entirely?
→ Redefine semantics, remove special cases
2. Can I CONSOLIDATE this complexity?
→ Pull down into one module, aggregate handlers
3. Can I HIDE this complexity?
→ Mask in implementation, use defaults
4. Can I CLARIFY this complexity?
→ Better names, strategic comments, meet conventions
Do NOT just move complexity around—reduce it.
| After | Next |
|---|---|
| Simplification done | Verify interface simplified |