Method fetch

packages/fetch/src/xfetch.js:203–285

(config, priority)

  }

  fetch (config, priority) {
    // 检查缓存
    // middleware chain
    const chain = []
    let promise = Promise.resolve(config)

    // use queue
    const request = (config) => {
      // 对config进行以下正规化处理：
      // 1. 检查config.url存在
      // 2. 抹平微信/支付宝header/headers字段差异
      // 3. 填充默认method为GET, method大写化
      // 4. 对于类GET请求将config.data移动合并至config.params(最终发送请求前进行统一序列化并拼接至config.url上)
      // 5. 对于类POST请求将config.emulateJSON实现为config.header['content-type'] = 'application/x-www-form-urlencoded'
      // 后续请求处理都应基于正规化后的config进行处理(proxy/mock/validate/serialize)
      XFetch.normalizeConfig(config)

      // 检查缓存
      const responsePromise = this.checkPreCache(config)
      if (responsePromise && typeof config.usePre.onUpdate !== 'function') {
        return responsePromise
      }

      try {
        const checkRes = this.checkValidator(config)
        const isWrong = (typeof checkRes === 'boolean' && !checkRes) || (isObject(checkRes) && !checkRes.valid)
        if (isWrong) {
          this.onValidatorError(`xfetch参数校验错误 ${checkRes.url} ${checkRes?.errorResult ? 'error:' + checkRes.errorResult : ''} ${checkRes?.warningResult ? 'warning:' + checkRes?.warningResult : ''}`)
        }
      } catch (e) {
        console.log('xfetch参数校验错误', e)
      }
      config = this.checkProxy(config) // proxy

      if (this.useBigInt) {
        config.useBigInt = this.useBigInt
      }

      let promise = this.queue ? this.queue.request(config, priority) : this.requestAdapter(config)
      // 后置拦截器
      const chain = []
      this.interceptors.response.forEach(function pushResponseInterceptors (interceptor) {
        chain.push(interceptor.fulfilled, interceptor.rejected)
      })
      while (chain.length) {
        promise = promise.then(chain.shift(), chain.shift())
      }

      // onlyConsumer=true是一种只消费缓存数据的模式，此模式下不会产生缓存数据
      if (config.usePre.enable && config.usePre.mode !== 'consumer') {
        const cacheKey = formatCacheKey(config.url)
        this.cacheRequestData[cacheKey] && (this.cacheRequestData[cacheKey].responsePromise = promise)
      }

      // 如果命中缓存，则将缓存 responsePromise 与最新 promise 竞速，返回最快的 promise
      if (responsePromise && typeof config.usePre.onUpdate === 'function') {
        const returnPromise = Promise.any([responsePromise, promise])
        returnPromise.then(response => {