fix(es/minifier): Fix minification of framer-motion by checking cons.termniates()

[sjchmiela]

Description:

Next.js 15 seems to minify parts of framer-motion's code in an invalid way, changing the meaning. The original function modifies the single definition variable as it changes meaning (see input.js):

• if definition is a function, it calls it and saves the return value as definition
• if definition is a string, it resolves animation variant based on value as name and saves the variant as definition
• if definition is again a function, it calls it again and saves the return value as definition again

However, swc seems to be not noticing that definition may be mutated between the calls and collapses all ifs into one:

// `resolveVariantFromProps` in framer-motion
// https://github.com/motiondivision/motion/blob/ecd97f7dce8954be300aa73ab6a96208437941c5/packages/framer-motion/src/render/utils/resolve-variants.ts#L31-L72
export function resolveVariantFromProps(props, definition, custom, visualElement) {
    if ("function" == typeof definition || ("string" == typeof definition && (definition = props.variants && props.variants[definition]), "function" == typeof definition)) {
        const [current, velocity] = getValueState(visualElement);
        definition = definition(void 0 !== custom ? custom : props.custom, current, velocity);
    }
    return definition;
}

which skips the first call to definition, first "resolution" step.

Note: I suspect the output.js may not be precisely what SWC may output as minified code (maybe there is a way to minify it further). It definitely differs from the current output though by the initial call and reassignment to definition.

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Latest commit: 91ed6a3

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[codspeed-hq]

CodSpeed Performance Report

Merging #9818 will not alter performance

_{Comparing sjchmiela:sjchmiela/add-framer-motion-test-case (91ed6a3) with main (512c91f)}

Summary

✅ 194 untouched benchmarks

[kdy1]

Thank you for reducing the edge case! Actually it's the most hard part of minifier work...

[Austaras]

A more simple example of why we need to check if cons terminates.

[kdy1]

Thank you!