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90 lines
2.9 KiB
JavaScript
90 lines
2.9 KiB
JavaScript
import composeArgs from './composeArgs.js'
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import composeArgsRight from './composeArgsRight.js'
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import replaceHolders from './replaceHolders.js'
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/** Used as the internal argument placeholder. */
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const PLACEHOLDER = '__lodash_placeholder__'
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/** Used to compose bitmasks for function metadata. */
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const WRAP_BIND_FLAG = 1
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const WRAP_BIND_KEY_FLAG = 2
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const WRAP_CURRY_BOUND_FLAG = 4
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const WRAP_CURRY_FLAG = 8
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const WRAP_ARY_FLAG = 128
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const WRAP_REARG_FLAG = 256
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/**
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* Merges the function metadata of `source` into `data`.
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*
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* Merging metadata reduces the number of wrappers used to invoke a function.
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* This is possible because methods like `bind`, `curry`, and `partial`
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* may be applied regardless of execution order. Methods like `ary` and
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* `rearg` modify function arguments, making the order in which they are
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* executed important, preventing the merging of metadata. However, we make
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* an exception for a safe combined case where curried functions have `ary`
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* and or `rearg` applied.
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*
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* @private
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* @param {Array} data The destination metadata.
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* @param {Array} source The source metadata.
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* @returns {Array} Returns `data`.
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*/
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function mergeData(data, source) {
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const bitmask = data[1]
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const srcBitmask = source[1]
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let newBitmask = bitmask | srcBitmask
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const isCommon = newBitmask < (WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG | WRAP_ARY_FLAG)
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const isCombo =
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((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_CURRY_FLAG)) ||
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((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_REARG_FLAG) && (data[7].length <= source[8])) ||
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((srcBitmask == (WRAP_ARY_FLAG | WRAP_REARG_FLAG)) && (source[7].length <= source[8]) && (bitmask == WRAP_CURRY_FLAG))
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// Exit early if metadata can't be merged.
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if (!(isCommon || isCombo)) {
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return data
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}
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// Use source `thisArg` if available.
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if (srcBitmask & WRAP_BIND_FLAG) {
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data[2] = source[2]
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// Set when currying a bound function.
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newBitmask |= bitmask & WRAP_BIND_FLAG ? 0 : WRAP_CURRY_BOUND_FLAG
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}
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// Compose partial arguments.
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let partials
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let value = source[3]
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if (value) {
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partials = data[3]
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data[3] = partials ? composeArgs(partials, value, source[4]) : value
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data[4] = partials ? replaceHolders(data[3], PLACEHOLDER) : source[4]
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}
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// Compose partial right arguments.
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value = source[5]
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if (value) {
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partials = data[5]
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data[5] = partials ? composeArgsRight(partials, value, source[6]) : value
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data[6] = partials ? replaceHolders(data[5], PLACEHOLDER) : source[6]
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}
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// Use source `argPos` if available.
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value = source[7]
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if (value) {
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data[7] = value
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}
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// Use source `ary` if it's smaller.
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if (srcBitmask & WRAP_ARY_FLAG) {
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data[8] = data[8] == null ? source[8] : Math.min(data[8], source[8])
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}
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// Use source `arity` if one is not provided.
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if (data[9] == null) {
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data[9] = source[9]
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}
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// Use source `func` and merge bitmasks.
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data[0] = source[0]
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data[1] = newBitmask
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return data
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}
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export default mergeData
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