| 1 | /*
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| 2 | MIT License http://www.opensource.org/licenses/mit-license.php
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| 3 | Author Tobias Koppers @sokra
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| 4 | */
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| 5 |
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| 6 | "use strict";
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| 7 |
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| 8 | const forEachBail = require("./forEachBail");
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| 9 | const { PathType, getType } = require("./util/path");
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| 10 |
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| 11 | /** @typedef {import("./Resolver")} Resolver */
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| 12 | /** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
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| 13 | /** @typedef {import("./Resolver").ResolveContext} ResolveContext */
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| 14 | /** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */
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| 15 | /** @typedef {import("./Resolver").ResolveCallback} ResolveCallback */
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| 16 | /** @typedef {string | string[] | false} Alias */
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| 17 | /** @typedef {{ alias: Alias, name: string, onlyModule?: boolean }} AliasOption */
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| 18 |
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| 19 | /**
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| 20 | * @typedef {object} CompiledAliasOption
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| 21 | * @property {string} name original alias name
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| 22 | * @property {string} nameWithSlash name + "/" — precomputed to avoid per-resolve concat
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| 23 | * @property {Alias} alias alias target(s)
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| 24 | * @property {boolean} onlyModule normalized onlyModule flag
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| 25 | * @property {string | null} absolutePath absolute form of `name` (with slash ending), null when not absolute
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| 26 | * @property {string | null} wildcardPrefix substring before the single "*" in `name`, null when no wildcard
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| 27 | * @property {string | null} wildcardSuffix substring after the single "*" in `name`, null when no wildcard
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| 28 | * @property {number} firstCharCode first character code of `name` — used as a cheap screen on the hot path. `-1` indicates "matches any first char" (empty wildcard prefix).
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| 29 | * @property {boolean} arrayAlias true when `alias` is an array — precomputed so the hot path skips `Array.isArray`
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| 30 | */
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| 31 |
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| 32 | /**
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| 33 | * Bucketed view of compiled options used by `aliasResolveHandler` to avoid
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| 34 | * walking the full option list on every resolve. The `all` array preserves
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| 35 | * the legacy linear order (declaration order) for the fallback path. The
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| 36 | * `byFirstChar` map buckets options by the first char code of their `name`
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| 37 | * — each bucket preserves declaration order among its members. The
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| 38 | * `hasAnyFirstChar` flag is true when at least one option matches any
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| 39 | * first char (`firstCharCode === -1`), in which case resolve-time scans
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| 40 | * fall back to `all` to keep declaration-order semantics across buckets.
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| 41 | * The `useBuckets` flag is true only when bucketing would actually help —
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| 42 | * i.e. there are at least 2 distinct first chars AND no empty-prefix
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| 43 | * wildcard. When false, the resolve hot path skips the `Map.get` and
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| 44 | * iterates `all` directly with the per-option first-char-code screen
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| 45 | * (matching the pre-bucketing behavior). This avoids paying for `Map.get`
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| 46 | * on degenerate single-bucket lists like a long chain of aliases that
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| 47 | * all share one first char — the bucket lookup adds overhead without
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| 48 | * narrowing the candidate set, which showed up as a transient-memory
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| 49 | * regression on `pathological-deep-stack`.
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| 50 | * @typedef {object} CompiledAliasOptions
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| 51 | * @property {CompiledAliasOption[]} all declaration-ordered list
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| 52 | * @property {Map<number, CompiledAliasOption[]>} byFirstChar bucketed by first char code
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| 53 | * @property {boolean} hasAnyFirstChar true when an empty-prefix wildcard is present
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| 54 | * @property {boolean} useBuckets true when the bucket fast-path should be used at resolve time
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| 55 | */
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| 56 |
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| 57 | const EMPTY_LIST = /** @type {CompiledAliasOption[]} */ ([]);
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| 58 | const EMPTY_COMPILED_OPTIONS = /** @type {CompiledAliasOptions} */ ({
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| 59 | all: EMPTY_LIST,
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| 60 | byFirstChar: new Map(),
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| 61 | hasAnyFirstChar: false,
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| 62 | useBuckets: false,
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| 63 | });
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| 64 |
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| 65 | /**
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| 66 | * Precompute per-option strings used on every resolve so the hot path in
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| 67 | * `aliasResolveHandler` does no string concatenation / split work per entry.
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| 68 | * Called once per plugin apply — the returned structure is stable for the
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| 69 | * lifetime of the resolver.
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| 70 | *
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| 71 | * Beyond the per-option precompute step, this also partitions the list into
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| 72 | * a `byFirstChar` map so that, when no "empty-prefix" wildcards are
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| 73 | * present, the resolve-time scan only walks options whose `name` starts
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| 74 | * with the same char as the current request. For large alias lists (300+
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| 75 | * entries) this turns an O(N) screen into O(K) where K is the bucket size
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| 76 | * for the request's first char.
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| 77 | * @param {Resolver} resolver resolver
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| 78 | * @param {AliasOption[]} options options
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| 79 | * @returns {CompiledAliasOptions} compiled options
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| 80 | */
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| 81 | function compileAliasOptions(resolver, options) {
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| 82 | if (options.length === 0) return EMPTY_COMPILED_OPTIONS;
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| 83 | const all = /** @type {CompiledAliasOption[]} */ (
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| 84 | Array.from({ length: options.length })
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| 85 | );
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| 86 | /** @type {Map<number, CompiledAliasOption[]>} */
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| 87 | const byFirstChar = new Map();
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| 88 | let hasAnyFirstChar = false;
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| 89 | for (let i = 0; i < options.length; i++) {
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| 90 | const item = options[i];
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| 91 | const { name } = item;
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| 92 | let absolutePath = null;
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| 93 | const type = getType(name);
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| 94 | if (type === PathType.AbsolutePosix || type === PathType.AbsoluteWin) {
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| 95 | absolutePath = resolver.join(name, "_").slice(0, -1);
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| 96 | }
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| 97 | const firstStar = name.indexOf("*");
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| 98 | let wildcardPrefix = null;
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| 99 | let wildcardSuffix = null;
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| 100 | if (firstStar !== -1 && !name.includes("*", firstStar + 1)) {
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| 101 | wildcardPrefix = name.slice(0, firstStar);
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| 102 | wildcardSuffix = name.slice(firstStar + 1);
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| 103 | }
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| 104 | // firstCharCode: used by `aliasResolveHandler` to quickly skip aliases
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| 105 | // whose name can't possibly match the current innerRequest. For a plain
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| 106 | // alias (no wildcard) the first char of the name is also the first char
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| 107 | // of `nameWithSlash` and of `absolutePath` (since the latter is derived
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| 108 | // from name via `resolver.join(name, "_")`, which only appends). For a
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| 109 | // wildcard with a non-empty prefix, the first char of that prefix is
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| 110 | // also the first char of name. Only the `name === "*"` case (empty
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| 111 | // wildcard prefix) can match arbitrary first chars — encode that as -1.
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| 112 | let firstCharCode;
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| 113 | if (wildcardPrefix !== null && wildcardPrefix.length === 0) {
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| 114 | firstCharCode = -1;
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| 115 | } else {
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| 116 | firstCharCode = name.length > 0 ? name.charCodeAt(0) : -1;
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| 117 | }
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| 118 | const compiled = {
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| 119 | name,
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| 120 | nameWithSlash: `${name}/`,
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| 121 | alias: item.alias,
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| 122 | onlyModule: Boolean(item.onlyModule),
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| 123 | absolutePath,
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| 124 | wildcardPrefix,
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| 125 | wildcardSuffix,
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| 126 | firstCharCode,
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| 127 | arrayAlias: Array.isArray(item.alias),
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| 128 | };
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| 129 | all[i] = compiled;
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| 130 | if (firstCharCode === -1) {
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| 131 | hasAnyFirstChar = true;
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| 132 | } else {
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| 133 | let bucket = byFirstChar.get(firstCharCode);
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| 134 | if (bucket === undefined) {
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| 135 | bucket = [];
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| 136 | byFirstChar.set(firstCharCode, bucket);
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| 137 | }
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| 138 | bucket.push(compiled);
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| 139 | }
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| 140 | }
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| 141 | // Only enable the bucket fast-path when it would actually help. With
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| 142 | // a single bucket (all aliases share one first char, e.g. a chain of
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| 143 | // `chain-0 -> chain-1 -> …` rewrites), the resolve-time `Map.get`
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| 144 | // does no discrimination — every request lands in that one bucket
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| 145 | // or in nothing — and the lookup is overhead compared to walking
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| 146 | // `all` with the per-option first-char-code screen. Requiring 2+
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| 147 | // distinct first chars matches the cases where bucketing has
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| 148 | // measurable benefit (huge-alias-* / large-alias-list / stack-churn).
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| 149 | const useBuckets = !hasAnyFirstChar && byFirstChar.size >= 2;
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| 150 | return { all, byFirstChar, hasAnyFirstChar, useBuckets };
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| 151 | }
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| 152 |
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| 153 | /** @typedef {(err?: null | Error, result?: null | ResolveRequest) => void} InnerCallback */
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| 154 | /**
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| 155 | * @param {Resolver} resolver resolver
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| 156 | * @param {CompiledAliasOptions} options compiled options
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| 157 | * @param {ResolveStepHook} target target
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| 158 | * @param {ResolveRequest} request request
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| 159 | * @param {ResolveContext} resolveContext resolve context
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| 160 | * @param {InnerCallback} callback callback
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| 161 | * @returns {void}
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| 162 | */
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| 163 | function aliasResolveHandler(
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| 164 | resolver,
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| 165 | options,
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| 166 | target,
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| 167 | request,
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| 168 | resolveContext,
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| 169 | callback,
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| 170 | ) {
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| 171 | if (options.all.length === 0) return callback();
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| 172 | const innerRequest = request.request || request.path;
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| 173 | if (!innerRequest) return callback();
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| 174 |
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| 175 | // Precompute values used in the inner scan loop so we don't recompute
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| 176 | // them per option. This is meaningful when `options` has hundreds of
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| 177 | // entries (e.g. monorepos with generated alias lists) — see the
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| 178 | // `huge-alias-list` / `huge-alias-miss` benchmarks.
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| 179 | const innerFirstCharCode = innerRequest.charCodeAt(0);
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| 180 | const hasRequestString = Boolean(request.request);
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| 181 |
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| 182 | // Dispatch through the first-char-code bucket when it actually
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| 183 | // narrows the candidate set (`useBuckets` requires 2+ distinct
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| 184 | // first chars and no empty-prefix wildcard). When the field has
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| 185 | // only one first-char bucket — e.g. a long chain of `chain-N`
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| 186 | // aliases that all start with the same char — every request lands
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| 187 | // in that one bucket or nothing, so `Map.get` is overhead vs. just
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| 188 | // walking `all` with the per-option char-code screen. Walking
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| 189 | // `all` also matches the pre-bucketing behavior and keeps the
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| 190 | // `pathological-deep-stack` allocation profile flat.
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| 191 | let scan;
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| 192 | if (options.useBuckets) {
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| 193 | const bucket = options.byFirstChar.get(innerFirstCharCode);
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| 194 | if (bucket === undefined) return callback();
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| 195 | scan = bucket;
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| 196 | } else {
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| 197 | scan = options.all;
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| 198 | }
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| 199 |
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| 200 | forEachBail(
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| 201 | scan,
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| 202 | (item, callback) => {
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| 203 | // Char-code screen left in for the fallback (`options.all`) path
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| 204 | // where the bucket dispatch above wasn't usable. In the bucket
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| 205 | // path this is always true and folds into a no-op.
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| 206 | const { firstCharCode } = item;
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| 207 | if (firstCharCode !== -1 && firstCharCode !== innerFirstCharCode) {
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| 208 | return callback();
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| 209 | }
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| 210 |
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| 211 | /** @type {boolean} */
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| 212 | let shouldStop = false;
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| 213 |
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| 214 | // For absolute-name aliases, accept the normalized
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| 215 | // `absolutePath` form as well as the raw `nameWithSlash`.
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| 216 | // `nameWithSlash` unconditionally appends `/`, so a raw
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| 217 | // windows request with native backslashes
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| 218 | // (e.g. `C:\\abs\\foo\\baz` against `name: "C:\\abs\\foo"`)
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| 219 | // otherwise fails `startsWith("C:\\abs\\foo/")` and is
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| 220 | // silently skipped. Mirroring the `absolutePath` check in
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| 221 | // both branches closes the gap without changing any
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| 222 | // existing matches.
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| 223 | const { absolutePath } = item;
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| 224 | const matchRequest =
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| 225 | innerRequest === item.name ||
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| 226 | (!item.onlyModule &&
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| 227 | ((hasRequestString && innerRequest.startsWith(item.nameWithSlash)) ||
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| 228 | (absolutePath !== null && innerRequest.startsWith(absolutePath))));
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| 229 |
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| 230 | const matchWildcard = !item.onlyModule && item.wildcardPrefix !== null;
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| 231 |
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| 232 | if (matchRequest || matchWildcard) {
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| 233 | /**
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| 234 | * @param {Alias} alias alias
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| 235 | * @param {(err?: null | Error, result?: null | ResolveRequest) => void} callback callback
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| 236 | * @returns {void}
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| 237 | */
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| 238 | const resolveWithAlias = (alias, callback) => {
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| 239 | if (alias === false) {
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| 240 | /** @type {ResolveRequest} */
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| 241 | const ignoreObj = {
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| 242 | ...request,
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| 243 | path: false,
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| 244 | };
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| 245 | if (typeof resolveContext.yield === "function") {
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| 246 | resolveContext.yield(ignoreObj);
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| 247 | return callback(null, null);
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| 248 | }
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| 249 | return callback(null, ignoreObj);
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| 250 | }
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| 251 |
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| 252 | let newRequestStr;
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| 253 |
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| 254 | if (
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| 255 | matchWildcard &&
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| 256 | innerRequest.startsWith(
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| 257 | /** @type {string} */ (item.wildcardPrefix),
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| 258 | ) &&
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| 259 | innerRequest.endsWith(/** @type {string} */ (item.wildcardSuffix))
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| 260 | ) {
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| 261 | const match = innerRequest.slice(
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| 262 | /** @type {string} */ (item.wildcardPrefix).length,
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| 263 | innerRequest.length -
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| 264 | /** @type {string} */ (item.wildcardSuffix).length,
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| 265 | );
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| 266 | newRequestStr = alias.toString().replace("*", match);
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| 267 | }
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| 268 |
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| 269 | if (
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| 270 | matchRequest &&
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| 271 | innerRequest !== alias &&
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| 272 | !innerRequest.startsWith(`${alias}/`)
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| 273 | ) {
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| 274 | /** @type {string} */
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| 275 | const remainingRequest = innerRequest.slice(item.name.length);
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| 276 | newRequestStr = alias + remainingRequest;
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| 277 | }
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| 278 |
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| 279 | if (newRequestStr !== undefined) {
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| 280 | shouldStop = true;
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| 281 | /** @type {ResolveRequest} */
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| 282 | const obj = {
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| 283 | ...request,
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| 284 | request: newRequestStr,
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| 285 | fullySpecified: false,
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| 286 | };
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| 287 | return resolver.doResolve(
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| 288 | target,
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| 289 | obj,
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| 290 | `aliased with mapping '${item.name}': '${alias}' to '${newRequestStr}'`,
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| 291 | resolveContext,
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| 292 | (err, result) => {
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| 293 | if (err) return callback(err);
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| 294 | if (result) return callback(null, result);
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| 295 | return callback();
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| 296 | },
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| 297 | );
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| 298 | }
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| 299 | return callback();
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| 300 | };
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| 301 |
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| 302 | /**
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| 303 | * @param {(null | Error)=} err error
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| 304 | * @param {(null | ResolveRequest)=} result result
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| 305 | * @returns {void}
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| 306 | */
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| 307 | const stoppingCallback = (err, result) => {
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| 308 | if (err) return callback(err);
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| 309 |
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| 310 | if (result) return callback(null, result);
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| 311 | // Don't allow other aliasing or raw request
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| 312 | if (shouldStop) return callback(null, null);
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| 313 | return callback();
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| 314 | };
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| 315 |
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| 316 | if (item.arrayAlias) {
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| 317 | return forEachBail(
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| 318 | /** @type {string[]} */ (item.alias),
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| 319 | resolveWithAlias,
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| 320 | stoppingCallback,
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| 321 | );
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| 322 | }
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| 323 | return resolveWithAlias(item.alias, stoppingCallback);
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| 324 | }
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| 325 |
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| 326 | return callback();
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| 327 | },
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| 328 | callback,
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| 329 | );
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| 330 | }
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| 331 |
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| 332 | module.exports.aliasResolveHandler = aliasResolveHandler;
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| 333 | module.exports.compileAliasOptions = compileAliasOptions;
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