Function htmlEnvHook

packages/vite/src/node/plugins/html.ts:1282–1326

(config: ResolvedConfig)

 * Support `%ENV_NAME%` syntax in html files
 */
export function htmlEnvHook(config: ResolvedConfig): IndexHtmlTransformHook {
  const pattern = /%(\S+?)%/g
  const envPrefix = resolveEnvPrefix({ envPrefix: config.envPrefix })
  const env: Record<string, any> = { ...config.env }

  // account for user env defines
  for (const key in config.define) {
    if (key.startsWith(`import.meta.env.`)) {
      const val = config.define[key]
      if (typeof val === 'string') {
        try {
          const parsed = JSON.parse(val)
          env[key.slice(16)] = typeof parsed === 'string' ? parsed : val
        } catch {
          env[key.slice(16)] = val
        }
      } else {
        env[key.slice(16)] = JSON.stringify(val)
      }
    }
  }
  return (html, ctx) => {
    return html.replace(pattern, (text, key) => {
      if (key in env) {
        return env[key]
      } else {
        if (envPrefix.some((prefix) => key.startsWith(prefix))) {
          const relativeHtml = normalizePath(
            path.relative(config.root, ctx.filename),
          )
          config.logger.warn(
            colors.yellow(
              colors.bold(
                `(!) ${text} is not defined in env variables found in /${relativeHtml}. ` +
                  `Is the variable mistyped?`,
              ),
            ),
          )
        }

        return text
      }
    })
  }
}

export function injectNonceAttributeTagHook(
  config: ResolvedConfig,