yagni-review

name

yagni-review

description

Review diffs for over-engineering only. Finds what to delete: reinvented standard library, unneeded dependencies, speculative abstractions, dead flexibility. One line per finding with tag and replacement. Use when the user says "review for over-engineering", "what can we delete", "is this over-engineered", "simplify review", "yagni review", or invokes /yagni-review. Complements correctness-focused /review — this one only hunts complexity.

YAGNI Review

Review the current branch's diff against main for unnecessary complexity. One line per finding: location, what to cut, what replaces it. The diff's best outcome is getting shorter.

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Scope

Over-engineering and complexity only. Correctness bugs, security holes, and performance are explicitly out of scope — route them to /review.

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Step 1: Get the Diff

git diff main...HEAD

If main doesn't exist locally, try origin/main, then master.

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Step 2: Classify Findings

For each finding, assign one tag:

Tag	What to cut	Replacement
delete:	Dead code, unused flexibility, speculative feature	Nothing — remove it
stdlib:	Hand-rolled thing the standard library ships	Name the function/class
native:	Dependency or code doing what the platform already does	Name the native feature
yagni:	Abstraction with one implementation, config nobody sets, layer with one caller	Inline until a second use exists
shrink:	Same logic, fewer lines	Show the shorter form

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Step 3: Format Output

One line per finding:

L<line>: <tag> <what>. <replacement>.

For multi-file diffs: <file>:L<line>: <tag> <what>. <replacement>.

Examples

L12-38: stdlib: 27-line email validator class. "@" check + confirmation email, 1 line.
L4: native: moment.js imported for one format call. Intl.DateTimeFormat, 0 deps.
repo.py:L88: yagni: AbstractRepository with one implementation. Inline it.
L52-71: delete: retry wrapper around an idempotent local call. Nothing replaces it.
L30-44: shrink: manual loop builds dict. dict(zip(keys, values)), 1 line.

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Step 4: Score

End with the only metric that matters:

net: -<N> lines possible.

If there is nothing to cut, say Lean already. Ship. and stop.

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Boundaries

• Scope: over-engineering and complexity only.
• Correctness bugs, security holes, performance are out of scope — route to /review.
• A single smoke test or assert-based self-check is the minimum, not bloat — never flag it.
• Does not apply the fixes, only lists them.

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Optional: Persist Findings

If the user wants to track deferred findings, mark them with deferred: comments in the code (format: # deferred: <ceiling>, <upgrade path>). Then run /debt-ledger to harvest them into a ledger.