Function mapPatternToSource

packages/cli/src/cli/utils/buckets.ts:280–316

(
  pattern: string[],
  source: string[],
  locale: string,
  fullPattern: string,
  fullSource: string,
)

// [locale] segment when ** admits multiple valid alignments, the caller must
// validate uniqueness via `hasAmbiguousLocaleMapping` below.
function mapPatternToSource(
  pattern: string[],
  source: string[],
  locale: string,
  fullPattern: string,
  fullSource: string,
): { patToSrc: number[] } {
  const result = alignPatternToSource(pattern, source, locale);

  if (!result) {
    throw new CLIError({
      message: `Pattern "${fullPattern}" matched file "${fullSource}" via glob, but pattern segments could not be aligned with source segments. This is usually caused by ambiguous wildcard placement.`,
      docUrl: "ambiguousPathPattern",
    });
  }

  // For every [locale]-bearing pattern segment, verify there is no alternative
  // alignment that maps it to a different source index. Multiple valid
  // alignments that agree on [locale] positions (e.g. "**/**" against "a/b")
  // are fine; alignments that disagree are not, because the downstream
  // placeholder restoration would produce a different output path.
  for (let i = 0; i < pattern.length; i += 1) {
    if (!pattern[i].includes("[locale]")) continue;
    const chosen = result.patToSrc[i];
    const alternative = alignPatternToSource(pattern, source, locale, {
      forbid: { patternIndex: i, sourceIndex: chosen },
    });
    if (alternative) {
      throw new CLIError({
        message: `Pattern "${fullPattern}" matched file "${fullSource}" via glob, but the [locale] segment "${pattern[i]}" can be aligned to multiple positions in the source path. Anchor the pattern with literal directory names so [locale] has a unique placement.`,
        docUrl: "ambiguousPathPattern",
      });
    }
  }

  return { patToSrc: result.patToSrc };
}

// Runs the alignment DFS once and returns the first patToSrc found, or null if
// none exists. The optional `forbid` constraint disallows assigning a given