Function defineImport

packages/vite/src/node/ssr/ssrTransform.ts:97–135

(
    index: number,
    importNode: (
      | ESTree.ImportDeclaration
      | (ESTree.ExportNamedDeclaration & { source: ESTree.StringLiteral })
      | ESTree.ExportAllDeclaration
    ) & {
      start: number
      end: number
    },
    metadata?: DefineImportMetadata,
  )

  let hoistIndex = fileStartIndex

  function defineImport(
    index: number,
    importNode: (
      | ESTree.ImportDeclaration
      | (ESTree.ExportNamedDeclaration & { source: ESTree.StringLiteral })
      | ESTree.ExportAllDeclaration
    ) & {
      start: number
      end: number
    },
    metadata?: DefineImportMetadata,
  ) {
    const source = importNode.source.value
    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.