react-native-fast-image/src/warnings.ts

FastImage, performant React Native image component.

// FastImage's development warnings and errors, each once per app (a list would
// repeat it for every image), shared by the native (index.tsx) and web
// (index.web.tsx) versions.
import { Children } from 'react'
import type { ReactNode } from 'react'

const warned = new Set<string>()

export function warnOnce(
    key: string,
    message: string,
    level: 'warn' | 'error',
) {
    if (!warned.has(key)) {
        warned.add(key)
        console[level](message)
    }
}

// For the tests (test/setup.ts): `bun test` loads this module once for the
// native and web versions' tests together.
export function resetWarnings() {
    warned.clear()
}

// FastImage doesn't render children: on native it's a single view, and the
// web version does the same. toArray, as a Touchable clones its child with
// children: undefined.
export function warnIfChildren(children: unknown) {
    if (Children.toArray(children as ReactNode).length > 0) {
        warnOnce(
            'children',
            "react-native-fast-image: FastImage doesn't render children (since 10.0): use FastImageBackground for content over an image.",
            'error',
        )
    }
}