Function tryFsResolve

packages/vite/src/node/plugins/resolve.ts:553–576

(
  fsPath: string,
  options: InternalResolveOptions,
  tryIndex = true,
  skipPackageJson = false,
)

}

export function tryFsResolve(
  fsPath: string,
  options: InternalResolveOptions,
  tryIndex = true,
  skipPackageJson = false,
): string | undefined {
  // Dependencies like es5-ext use `#` in their paths. We don't support `#` in user
  // source code so we only need to perform the check for dependencies.
  // We don't support `?` in node_modules paths, so we only need to check in this branch.
  const hashIndex = fsPath.indexOf('#')
  if (hashIndex >= 0 && isInNodeModules(fsPath)) {
    const queryIndex = fsPath.indexOf('?')
    // We only need to check foo#bar?baz and foo#bar, ignore foo?bar#baz
    if (queryIndex < 0 || queryIndex > hashIndex) {
      const file = queryIndex > hashIndex ? fsPath.slice(0, queryIndex) : fsPath
      const res = tryCleanFsResolve(file, options, tryIndex, skipPackageJson)
      if (res) return res + fsPath.slice(file.length)
    }
  }

  const { file, postfix } = splitFileAndPostfix(fsPath)
  const res = tryCleanFsResolve(file, options, tryIndex, skipPackageJson)
  if (res) return res + postfix
}

const knownTsOutputRE = /\.(?:js|mjs|cjs|jsx)$/
const isPossibleTsOutput = (url: string): boolean => knownTsOutputRE.test(url)