Simplifying Code

Simplifying Code

Principles

| Principle | Rule | |-----------|------| | Preserve behavior | Output must do exactly what the input did -- no silent feature additions or removals. Specifically preserve: async/sync boundaries (do not convert sync to async or reverse), error propagation paths (do not alter strategy), logging/telemetry/guards/retries that encode operational intent, and domain-specific steps (do not collapse into generic helpers that hide intent) | | Explicit over clever | Prefer explicit variables over nested expressions. Readable beats compact | | Simplicity over cleanliness | Prefer straightforward code over pattern-heavy "clean" code. Three similar lines beat a premature abstraction | | Surgical changes | Touch only what needs simplifying. Match existing style, naming conventions, and formatting of the surrounding code | | Surface assumptions | Before changing a block, identify what imports it, what it imports, and what tests cover it. Edit dependents in the same pass |

Process

1. Read first -- understand the full file and its dependents before changing anything. Apply Chesterton's Fence: if you see code that looks unnecessary but don't understand why it's there, check git blame before removing it. First understand the reason, then decide if the reason still applies.
2. Identify invariants -- what must stay the same? Public API, return types, side effects, error behavior
3. Identify targets -- find the highest-impact simplification opportunities. Impact = readability and maintainability; prioritize: control flow -> naming -> duplication -> types (see Smell -> Fix table)
4. Apply in order -- control flow → naming → duplication → data shaping → types. Structural changes first, cosmetic last
5. Verify -- confirm no behavior change: tests pass, types check, imports resolve
6. Pre-submit scope audit -- walk every changed line and ask "does the requested task explicitly require this line?" If no, revert it and list it as a follow-up under Residual Risks. Drive-by edits belong in a separate change, not the current patch. For the pre-edit complement on ambiguous-scope requests ("simplify my project"), see ia-verification-before-completion's Scope Confirmation gate.

Smell → Fix

| Smell | Fix | |-------|-----| | Deep nesting (>2 levels) | Guard clauses with early returns | | Long function (>20 lines) | Extract into named functions by responsibility | | Too many parameters (>3) | Group into an options/config object | | Duplicated block (3+ occurrences) | Extract shared function. Two copies = leave inline; wait for the third | | Magic numbers/strings | Named constants | | Complex conditional | Extract to descriptively-named boolean or function | | Boolean-returning if/else (each branch returns a literal True/False) | Collapse to the boolean expression itself: return a and b, not a branch per literal | | Dense transform chain (3+ chained methods) | Break into named intermediates for debuggability | | Dead code / unreachable branches | Delete entirely -- no commented-out code | | Unnecessary else after return | Remove else, dedent |

AI Slop Removal

When simplifying AI-generated code, specifically target:

• Redundant comments that restate the code (// increment counter above counter++) -- delete them
• Unnecessary defensive checks for conditions that cannot occur in context -- remove the guard
• Gratuitous type casts (as any, as unknown as T) -- fix the actual type or use a proper generic
• Over-abstraction (factory for 2 objects, wrapper around a single call, util file with 1 function) -- inline the code
• Inconsistent style that drifts from the file's existing conventions -- match the file
• Placeholder stubs (// ..., // rest of code, // similar to above, // continue pattern, // add more as needed) -- leave unsimplified code as-is rather than replacing it with stubs
• Redundant error wrapping (catch(e) { throw e; }, catch(e) { throw new Error(e.message); }) that strips the original stack for no reason -- remove the try/catch entirely and let errors propagate
• Verbose stdlib reimplementations (hand-rolled loops that replicate array_filter, Array.from, Collection::pluck(), itertools) -- replace with the stdlib/framework one-liner, but verify edge-case parity first: empty input, null/None guard, no-match default, zero-value path. The one-liner can silently differ from the loop (an empty-input crash, a missing no-match default, lost ordering) -- a structurally cleaner version that changes behavior on an edge case is not a simplification

Stop Conditions

Stop and ask before proceeding when:

• Simplification requires changing a public API (function signatures, return types, exports)
• Behavior parity cannot be verified (no tests exist and behavior is non-obvious)
• Code is intentionally complex for domain reasons (performance-critical, protocol compliance)
• Scope implies a redesign rather than a simplification

Constraints

• Only simplify what was requested -- do not add features, expand scope, introduce new dependencies, or add speculative configurability or flexibility the request did not ask for
• Leave unchanged code untouched -- do not add comments, docstrings, or type annotations to lines that were not simplified
• Do not bundle unrelated cleanups into one patch -- each simplification should be a coherent, reviewable unit
• Do not introduce framework-wide patterns while simplifying a small local change
• Do not replace understandable duplication with opaque utility layers -- three similar lines are better than a premature abstraction
• Keep comments that explain intent, invariants, or non-obvious constraints. Remove comments that restate obvious code behavior.
• If a simplification would make the code harder to understand, skip it
• Watch for over-simplification: inlining too aggressively removes names that gave concepts meaning; combining unrelated logic into one function hides distinct responsibilities; removing abstractions that exist for testability breaks the test suite
• When unsure whether a block is dead code, ask instead of deleting

Verify

• Tests pass and types check after changes
• No behavior change (same inputs produce same outputs)
• Scope limited to requested files -- no drive-by cleanups
• Match test scope to the importer count surfaced in step 1 (Surface assumptions). Zero external importers: scoped tests on the changed paths. One or more external importers, or shared/utility code edited: run tests covering each importer. Run the full suite when the test runner has no path-scoping mechanism.

Orchestrator Mode (When Chained With Other Skills)

When this skill is invoked by an orchestrator that also runs ia-code-review, ia-writing-tests, or ia-verification-before-completion on the same scope, each sub-skill re-resolving scope independently wastes tokens and risks drift. Avoid this by resolving scope exactly once and passing a canonical block to every sub-skill.

Resolved scope format — the orchestrator builds this once, before dispatching any sub-skill:

## Resolved scope
Files:
- path/to/file-a.ts
- path/to/file-b.ts

Commit range: HEAD~3..HEAD (or "uncommitted")

Intent: [one-sentence description pulled from the user request or PR description]

Constraints:
- Preserve public API
- No behavior change
- [other constraints specific to this run]

Every chained sub-skill receives this block verbatim in its prompt and uses it as the source of truth — no re-running git diff --name-only, no re-parsing the user request, no independent scope resolution. Sub-skills accept --no-verify --no-report flags when chained so verification and reporting happen once at the end of the chain, not per-skill. The last sub-skill in the chain runs verification; the orchestrator trusts that result rather than re-verifying.

This prevents two failure modes: scope drift (sub-skill A simplifies one set of files, sub-skill B reviews a different set) and double work (every sub-skill rediscovers the same facts).

Integration

• ia-code-simplicity-reviewer agent -- analysis-only pass producing a simplification report (no code changes). Use before refactoring to identify targets.

Output

After simplifying, report:

• Scope touched: files and functions modified
• Key simplifications: what changed and why (one line each)
• Verification: tests pass, types check, no behavior change
• Residual risks: assumptions made, areas not touched that may need attention

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: iliaal
• Source: iliaal/ai-skills
• License: MIT

Install and usage instructions live in the source repository linked above.