Function postImportMapHook

packages/vite/src/node/plugins/html.ts:1205–1259

(
  config: ResolvedConfig,
)

 * Move importmap before the first module script and modulepreload link
 */
export function postImportMapHook(
  config: ResolvedConfig,
): IndexHtmlTransformHook {
  const decoder = new TextDecoder()
  return function (html, { bundle }) {
    const chunkImportMapEnabled =
      config.command === 'build' && config.build.chunkImportMap

    if (importMapAppendRE.test(html)) {
      let importMap: string | undefined
      html = html.replace(importMapRE, (match) => {
        importMap = match
        return ''
      })

      if (importMap) {
        html = html.replace(
          importMapAppendRE,
          (match) => `${importMap}\n${match}`,
        )
        if (chunkImportMapEnabled) {
          // https://caniuse.com/mdn-html_elements_script_type_importmap_multiple_import_maps
          this.warn(
            `The \`build.chunkImportMap\` option is enabled but an import map also exists in the input HTML file.` +
              ` This leads to multiple import maps generated in the output HTML, which is not supported by older browsers and Firefox.`,
          )
        }
      }
    }

    if (chunkImportMapEnabled) {
      const nonce = config.html?.cspNonce
      const importMap = bundle![getImportMapFilename(config)] as OutputAsset
      const importMapHtml = serializeTag({
        tag: 'script',
        attrs: { type: 'importmap', ...(nonce ? { nonce } : {}) },
        children:
          typeof importMap.source === 'string'
            ? importMap.source
            : decoder.decode(importMap.source),
      })
      if (importMapAppendRE.test(html)) {
        // NOTE: insert before the existing import map so that our import map takes precedence
        html = html.replace(
          importMapAppendRE,
          (match) => `${importMapHtml}\n${match}`,
        )
      } else {
        html = `${importMapHtml}\n${html}`
      }
    }

    return html
  }
}

export function injectCspNonceMetaTagHook(
  config: ResolvedConfig,