axios/lib/adapters/fetch.js

import platform from "../platform/index.js";
import utils from "../utils.js";
import AxiosError from "../core/AxiosError.js";
import composeSignals from "../helpers/composeSignals.js";
import {trackStream} from "../helpers/trackStream.js";
import AxiosHeaders from "../core/AxiosHeaders.js";
import progressEventReducer from "../helpers/progressEventReducer.js";
import resolveConfig from "../helpers/resolveConfig.js";
import settle from "../core/settle.js";

const fetchProgressDecorator = (total, fn) => {
  const lengthComputable = total != null;
  return (loaded) => setTimeout(() => fn({
    lengthComputable,
    total,
    loaded
  }));
}

const isFetchSupported = typeof fetch !== 'undefined';

const supportsRequestStreams = isFetchSupported && (() => {
  let duplexAccessed = false;

  const hasContentType = new Request(platform.origin, {
    body: new ReadableStream(),
    method: 'POST',
    get duplex() {
      duplexAccessed = true;
      return 'half';
    },
  }).headers.has('Content-Type');

  return duplexAccessed && !hasContentType;
})();

const DEFAULT_CHUNK_SIZE = 64 * 1024;

const resolvers = {
  stream: (res) => res.body
};

isFetchSupported && ['text', 'arrayBuffer', 'blob', 'formData'].forEach(type => [
  resolvers[type] = utils.isFunction(Response.prototype[type]) ? (res) => res[type]() : (_, config) => {
    throw new AxiosError(`Response type ${type} is not supported`, AxiosError.ERR_NOT_SUPPORT, config);
  }
])

const getBodyLength = async (body) => {
  if(utils.isBlob(body)) {
    return body.size;
  }

  if(utils.isSpecCompliantForm(body)) {
    return (await new Request(body).arrayBuffer()).byteLength;
  }

  if(utils.isArrayBufferView(body)) {
    return body.byteLength;
  }

  if(utils.isURLSearchParams(body)) {
    body = body + '';
  }

  if(utils.isString(body)) {
    return (await new TextEncoder().encode(body)).byteLength;
  }
}

const resolveBodyLength = async (headers, body) => {
  const length = utils.toFiniteNumber(headers.getContentLength());

  return length == null ? getBodyLength(body) : length;
}

export default async (config) => {
  let {
    url,
    method,
    data,
    signal,
    cancelToken,
    timeout,
    onDownloadProgress,
    onUploadProgress,
    responseType,
    headers,
    withCredentials = 'same-origin',
    fetchOptions
  } = resolveConfig(config);

  responseType = responseType ? (responseType + '').toLowerCase() : 'text';

  let [composedSignal, stopTimeout] = (signal || cancelToken || timeout) ?
    composeSignals([signal, cancelToken], timeout) : [];

  let finished, request;

  const onFinish = () => {
    !finished && setTimeout(() => {
      composedSignal && composedSignal.unsubscribe();
    });

    finished = true;
  }

  try {
    if (onUploadProgress && supportsRequestStreams && method !== 'get' && method !== 'head') {
      let requestContentLength = await resolveBodyLength(headers, data);

      let _request = new Request(url, {
        method,
        body: data,
        duplex: "half"
      });

      let contentTypeHeader;

      if (utils.isFormData(data) && (contentTypeHeader = _request.headers.get('content-type'))) {
        headers.setContentType(contentTypeHeader)
      }

      data = trackStream(_request.body, DEFAULT_CHUNK_SIZE, fetchProgressDecorator(
        requestContentLength,
        progressEventReducer(onUploadProgress)
      ));
    }

    if (!utils.isString(withCredentials)) {
      withCredentials = withCredentials ? 'cors' : 'omit';
    }

    request = new Request(url, {
      ...fetchOptions,
      signal: composedSignal,
      method,
      headers: headers.normalize().toJSON(),
      body: data,
      duplex: "half",
      withCredentials
    });

    let response = await fetch(request);

    const isStreamResponse = responseType === 'stream' || responseType === 'response';

    if (onDownloadProgress || isStreamResponse) {
      const options = {};

      Object.getOwnPropertyNames(response).forEach(prop => {
        options[prop] = response[prop];
      });

      const responseContentLength = utils.toFiniteNumber(response.headers.get('content-length'));

      response = new Response(
        trackStream(response.body, DEFAULT_CHUNK_SIZE, onDownloadProgress && fetchProgressDecorator(
          responseContentLength,
          progressEventReducer(onDownloadProgress, true)
        ), isStreamResponse && onFinish),
        options
      );
    }

    responseType = responseType || 'text';

    let responseData = await resolvers[utils.findKey(resolvers, responseType) || 'text'](response, config);

    !isStreamResponse && onFinish();

    stopTimeout && stopTimeout();

    return await new Promise((resolve, reject) => {
      settle(resolve, reject, {
        data: responseData,
        headers: AxiosHeaders.from(response.headers),
        status: response.status,
        statusText: response.statusText,
        config,
        request
      })
    })
  } catch (err) {
    onFinish();

    let {code} = err;

    if (err.name === 'NetworkError') {
      code = AxiosError.ERR_NETWORK;
    }

    throw AxiosError.from(err, code, config, request);
  }
}