54 lines
1.9 KiB
Plaintext
54 lines
1.9 KiB
Plaintext
import type { AnyFunction } from '../types'
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/**
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* Runs a check to determine if the given result function behaves as an
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* identity function. An identity function is one that returns its
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* input unchanged, for example, `x => x`. This check helps ensure
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* efficient memoization and prevent unnecessary re-renders by encouraging
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* proper use of transformation logic in result functions and
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* extraction logic in input selectors.
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*
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* @param resultFunc - The result function to be checked.
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* @param inputSelectorsResults - The results of the input selectors.
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* @param outputSelectorResult - The result of the output selector.
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*
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* @see {@link https://reselect.js.org/api/development-only-stability-checks#identityfunctioncheck `identityFunctionCheck`}
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*
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* @since 5.0.0
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* @internal
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*/
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export const runIdentityFunctionCheck = (
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resultFunc: AnyFunction,
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inputSelectorsResults: unknown[],
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outputSelectorResult: unknown
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) => {
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if (
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inputSelectorsResults.length === 1 &&
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inputSelectorsResults[0] === outputSelectorResult
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) {
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let isInputSameAsOutput = false
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try {
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const emptyObject = {}
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if (resultFunc(emptyObject) === emptyObject) isInputSameAsOutput = true
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} catch {
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// Do nothing
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}
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if (isInputSameAsOutput) {
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let stack: string | undefined = undefined
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try {
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throw new Error()
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} catch (e) {
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// eslint-disable-next-line @typescript-eslint/no-extra-semi, no-extra-semi
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;({ stack } = e as Error)
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}
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console.warn(
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'The result function returned its own inputs without modification. e.g' +
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'\n`createSelector([state => state.todos], todos => todos)`' +
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'\nThis could lead to inefficient memoization and unnecessary re-renders.' +
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'\nEnsure transformation logic is in the result function, and extraction logic is in the input selectors.',
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{ stack }
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)
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}
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}
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}
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