ssrTransformScript() — vite Function Reference

Source Code

packages/vite/src/node/ssr/ssrTransform.ts lines 82–453

async function ssrTransformScript(
  code: string,
  inMap: SourceMap | { mappings: '' } | null,
  url: string,
  originalCode: string,
): Promise<TransformResult | null> {
  const s = new MagicString(code)

  let ast: any
  try {
    ast = await rolldownParseAstAsync(code)
  } catch (err) {
    // enhance known rollup errors
    // https://github.com/rollup/rollup/blob/42e587e0e37bc0661aa39fe7ad6f1d7fd33f825c/src/utils/bufferToAst.ts#L17-L22
    if (err.code === 'PARSE_ERROR') {
      err.message = `Parse failure: ${err.message}\n`
      err.id = url
      if (typeof err.pos === 'number') {
        err.loc = numberToPos(code, err.pos)
        err.loc.file = url
        err.frame = generateCodeFrame(code, err.pos)
        err.message += `At file: ${url}:${err.loc.line}:${err.loc.column}`
      } else {
        err.message += `At file: ${url}`
      }
    }
    throw err
  }

  let uid = 0
  const deps = new Set<string>()
  const dynamicDeps = new Set<string>()
  const idToImportMap = new Map<string, string>()
  const declaredConst = new Set<string>()

  // hoist at the start of the file, after the hashbang
  const fileStartIndex = hashbangRE.exec(code)?.[0].length ?? 0
  let hoistIndex = fileStartIndex

  function defineImport(
    index: number,
    importNode: (
      | ImportDeclaration
      | (ExportNamedDeclaration & { source: Literal })
      | ExportAllDeclaration
    ) & {
      start: number
      end: number
    },
    metadata?: DefineImportMetadata,
  ) {
    const source = importNode.source.value as string
    deps.add(source)

    // Reduce metadata to undefined if it's all default values
    const metadataArg =
      (metadata?.importedNames?.length ?? 0) > 0
        ? `, ${JSON.stringify(metadata)}`
        : ''

    const importId = `__vite_ssr_import_${uid++}__`
    const transformedImport = `const ${importId} = await ${ssrImportKey}(${JSON.stringify(
      source,
    )}${metadataArg});\n`

    s.update(importNode.start, importNode.end, transformedImport)

    if (importNode.start === index) {
      // no need to hoist, but update hoistIndex to keep the order
      hoistIndex = importNode.end
    } else {
      // There will be an error if the module is called before it is imported,
      // so the module import statement is hoisted to the top
      s.move(importNode.start, importNode.end, index)
    }

    return importId
  }

  function defineExport(name: string, local = name) {
    // wrap with try/catch to fallback to `undefined` for backward compat.