Function create_esm_wrapper

tools/link.py:2152–2191

(wrapper_file, support_target, wasm_target)

def create_esm_wrapper(wrapper_file, support_target, wasm_target):
  js_exports = building.user_requested_exports.union(settings.EXPORTED_RUNTIME_METHODS)
  js_exports = ', '.join(sorted(js_exports))

  wrapper = []
  wrapper.append('// The wasm module must be imported here first before the support file')
  wrapper.append('// in order to avoid issues with circular dependencies.')
  wrapper.append(f"import * as unused from './{settings.WASM_BINARY_FILE}';")
  support_url = f'./{os.path.basename(support_target)}'
  if js_exports:
    wrapper.append(f"export {{ default, {js_exports} }} from '{support_url}';")
  else:
    wrapper.append(f"export {{ default }} from '{support_url}';")

  if settings.ENVIRONMENT_MAY_BE_NODE:
    wrapper.append(f'''
// When run as the main module under node, create the module directly.  This will
// execute any startup code along with main (if it exists).
import init from '{support_url}';
const isNode = {node_detection_code()};
if (isNode) {{
  const url = await import('node:url');
  const isMainModule = url.pathToFileURL(process.argv[1]).href === import.meta.url;
  if (isMainModule) await init();
}}''')

  write_file(wrapper_file, '\n'.join(wrapper) + '\n')

  # FIXME(sbc): This is a huge hack to rename the imports in the
  # wasm file.  Find a better way to do this.
  wasm_dis = os.path.join(building.get_binaryen_bin(), 'wasm-dis')
  mod = shared.check_call([wasm_dis, wasm_target], stdout=PIPE).stdout
  mod = mod.replace('(import "env"', f'(import "{support_url}"')
  mod = mod.replace('(import "wasi_snapshot_preview1"', f'(import "{support_url}"')

  wasm_as = os.path.join(building.get_binaryen_bin(), 'wasm-as')
  cmd = [wasm_as, '--all-features', '-o', wasm_target, '-']
  if settings.EMIT_NAME_SECTION:
    cmd.append('-g')
  shared.check_call(cmd, input=mod)


def convert_line_endings_in_file(filename, to_eol):