`react-doctor/no-spread-accumulator-in-reduce`

Accumulator spread in reduce is quadratic

Category: Performance
Severity: warn
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: always
Tags: test-noise
Default: Enabled

Validate the diagnostic

Confirm the reported code matches this rule before you edit it.

Confirm the reported code matches react-doctor/no-spread-accumulator-in-reduce. Compare it with the Before example and verify the same API, framework, and execution context. Treat it as a false positive only when one of those conditions differs.

Compare the code

The corrected pattern shows a focused way to address the diagnostic.

Reported pattern

const valuesByKey = keys.reduce(
  (values, key) => ({ ...values, [key]: getValue(key) }),
  {},
);

Corrected pattern

const valuesByKey = Object.fromEntries(
  keys.map((key) => [key, getValue(key)]),
);

How to fix

Use the corrected pattern as a reference. Preserve behavior that the rule does not require you to change.

Copyable fix prompt

Copy this self-contained prompt into your coding agent after you confirm the diagnostic.

Fix every confirmed react-doctor/no-spread-accumulator-in-reduce diagnostic in the current repository. Required change: - Mutate the accumulator and return it (acc[key] = value; return acc) so the fold stays O(n) instead of copying the whole accumulator every step.

Reference transformation:Before:

const valuesByKey = keys.reduce(
  (values, key) => ({ ...values, [key]: getValue(key) }),
  {},
);

After:

const valuesByKey = Object.fromEntries(
  keys.map((key) => [key, getValue(key)]),
);

Constraints: - Confirm the reported code matches the Before pattern. - Make the smallest change that fixes the root cause. - Preserve behavior and interfaces unrelated to this diagnostic. - Reuse existing project components, utilities, and conventions. - Do not introduce render-phase side effects, render-phase state updates, or Hooks rule violations. - Preserve resource ownership and cleanup. Do not move work into a hotter render or frame path. - Adapt identifiers and framework details instead of copying blindly. - Do not disable the rule or suppress matching code. Verification: - Run focused tests for the changed behavior. - Run React Doctor and confirm this diagnostic no longer appears. - Report the files changed and any checks you could not run.

More Performance rules from the rules reference:

react-doctor/no-srcset-without-sizes: Responsive image omits sizes
react-doctor/no-sync-xhr: Synchronous XMLHttpRequest
react-doctor/no-tailwind-layout-transition: Animating a layout property
react-doctor/no-transition-all: List specific properties: `transition: "opacity 200ms, transform 200ms"` — or in Tailwind use `transition-colors`, `transition-opacity`, or `transition-transform`
react-doctor/no-unbounded-animation-frame-loop: Animation frame loop has no stop path

react-doctor/no-spread-accumulator-in-reduce