chore: align fetch to spec (#10203)

This commit aligns the `fetch` API and the `Request` / `Response`
classes belonging to it to the spec. This commit enables all the
relevant `fetch` WPT tests. Spec compliance is now at around 90%.

Performance is essentially identical now (within 1% of 1.9.0).

1 files changed, 229 insertions, 1067 deletions

diff --git a/op_crates/fetch/26_fetch.js b/op_crates/fetch/26_fetch.js
index d07121e86..a6d1608d0 100644
--- a/op_crates/fetch/26_fetch.js
+++ b/op_crates/fetch/26_fetch.js
@@ -13,497 +13,36 @@
 
 ((window) => {
   const core = window.Deno.core;
-
-  // provided by "deno_web"
-  const { URLSearchParams } = window.__bootstrap.url;
-  const { getLocationHref } = window.__bootstrap.location;
-  const { FormData, parseFormData, encodeFormData } =
-    window.__bootstrap.formData;
-  const { parseMimeType } = window.__bootstrap.mimesniff;
-
-  const { ReadableStream, isReadableStreamDisturbed } =
-    window.__bootstrap.streams;
-  const { Headers } = window.__bootstrap.headers;
-  const { Blob, _byteSequence, File } = window.__bootstrap.file;
-
-  const MAX_SIZE = 2 ** 32 - 2;
-
-  /**
-   * @param {Uint8Array} src 
-   * @param {Uint8Array} dst 
-   * @param {number} off the offset into `dst` where it will at which to begin writing values from `src`
-   * 
-   * @returns {number} number of bytes copied
-   */
-  function copyBytes(src, dst, off = 0) {
-    const r = dst.byteLength - off;
-    if (src.byteLength > r) {
-      src = src.subarray(0, r);
-    }
-    dst.set(src, off);
-    return src.byteLength;
-  }
-
-  class Buffer {
-    /** @type {Uint8Array} */
-    #buf; // contents are the bytes buf[off : len(buf)]
-    #off = 0; // read at buf[off], write at buf[buf.byteLength]
-
-    /** @param {ArrayBuffer} [ab] */
-    constructor(ab) {
-      if (ab == null) {
-        this.#buf = new Uint8Array(0);
-        return;
-      }
-
-      this.#buf = new Uint8Array(ab);
-    }
-
-    /**
-     * @returns {Uint8Array}
-     */
-    bytes(options = { copy: true }) {
-      if (options.copy === false) return this.#buf.subarray(this.#off);
-      return this.#buf.slice(this.#off);
-    }
-
-    /**
-     * @returns {boolean}
-     */
-    empty() {
-      return this.#buf.byteLength <= this.#off;
-    }
-
-    /**
-     * @returns {number}
-     */
-    get length() {
-      return this.#buf.byteLength - this.#off;
-    }
-
-    /**
-     * @returns {number}
-     */
-    get capacity() {
-      return this.#buf.buffer.byteLength;
-    }
-
-    /**
-     * @returns {void}
-     */
-    reset() {
-      this.#reslice(0);
-      this.#off = 0;
-    }
-
-    /**
-     * @param {number} n
-     * @returns {number}
-     */
-    #tryGrowByReslice = (n) => {
-      const l = this.#buf.byteLength;
-      if (n <= this.capacity - l) {
-        this.#reslice(l + n);
-        return l;
-      }
-      return -1;
-    };
-
-    /**
-     * @param {number} len
-     * @returns {void}
-     */
-    #reslice = (len) => {
-      if (!(len <= this.#buf.buffer.byteLength)) {
-        throw new Error("assert");
-      }
-      this.#buf = new Uint8Array(this.#buf.buffer, 0, len);
-    };
-
-    /**
-     * @param {Uint8Array} p
-     * @returns {number}
-     */
-    writeSync(p) {
-      const m = this.#grow(p.byteLength);
-      return copyBytes(p, this.#buf, m);
-    }
-
-    /**
-     * @param {Uint8Array} p
-     * @returns {Promise<number>}
-     */
-    write(p) {
-      const n = this.writeSync(p);
-      return Promise.resolve(n);
-    }
-
-    /** 
-     * @param {number} n
-     * @returns {number}
-     */
-    #grow = (n) => {
-      const m = this.length;
-      // If buffer is empty, reset to recover space.
-      if (m === 0 && this.#off !== 0) {
-        this.reset();
-      }
-      // Fast: Try to grow by means of a reslice.
-      const i = this.#tryGrowByReslice(n);
-      if (i >= 0) {
-        return i;
-      }
-      const c = this.capacity;
-      if (n <= Math.floor(c / 2) - m) {
-        // We can slide things down instead of allocating a new
-        // ArrayBuffer. We only need m+n <= c to slide, but
-        // we instead let capacity get twice as large so we
-        // don't spend all our time copying.
-        copyBytes(this.#buf.subarray(this.#off), this.#buf);
-      } else if (c + n > MAX_SIZE) {
-        throw new Error("The buffer cannot be grown beyond the maximum size.");
-      } else {
-        // Not enough space anywhere, we need to allocate.
-        const buf = new Uint8Array(Math.min(2 * c + n, MAX_SIZE));
-        copyBytes(this.#buf.subarray(this.#off), buf);
-        this.#buf = buf;
-      }
-      // Restore this.#off and len(this.#buf).
-      this.#off = 0;
-      this.#reslice(Math.min(m + n, MAX_SIZE));
-      return m;
-    };
-
-    /** 
-     * @param {number} n
-     * @returns {void}
-     */
-    grow(n) {
-      if (n < 0) {
-        throw Error("Buffer.grow: negative count");
-      }
-      const m = this.#grow(n);
-      this.#reslice(m);
-    }
-  }
-
-  /** 
-   * @param {unknown} x
-   * @returns {x is ArrayBufferView}
-   */
-  function isTypedArray(x) {
-    return ArrayBuffer.isView(x) && !(x instanceof DataView);
-  }
-
-  /** 
-   * @param {string} s
-   * @param {string} value
-   * @returns {boolean}
-   */
-  function hasHeaderValueOf(s, value) {
-    return new RegExp(`^${value}(?:[\\s;]|$)`).test(s);
-  }
-
-  /**
-   * @param {string} name 
-   * @param {BodyInit | null} bodySource 
-   */
-  function validateBodyType(name, bodySource) {
-    if (isTypedArray(bodySource)) {
-      return true;
-    } else if (bodySource instanceof ArrayBuffer) {
-      return true;
-    } else if (typeof bodySource === "string") {
-      return true;
-    } else if (bodySource instanceof ReadableStream) {
-      return true;
-    } else if (bodySource instanceof FormData) {
-      return true;
-    } else if (bodySource instanceof URLSearchParams) {
-      return true;
-    } else if (!bodySource) {
-      return true; // null body is fine
-    }
-    throw new TypeError(
-      `Bad ${name} body type: ${bodySource.constructor.name}`,
-    );
-  }
-
-  /**
-   * @param {ReadableStreamReader<Uint8Array>} stream 
-   * @param {number} [size] 
-   */
-  async function bufferFromStream(
-    stream,
-    size,
-  ) {
-    const encoder = new TextEncoder();
-    const buffer = new Buffer();
-
-    if (size) {
-      // grow to avoid unnecessary allocations & copies
-      buffer.grow(size);
-    }
-
-    while (true) {
-      const { done, value } = await stream.read();
-
-      if (done) break;
-
-      if (typeof value === "string") {
-        buffer.writeSync(encoder.encode(value));
-      } else if (value instanceof ArrayBuffer) {
-        buffer.writeSync(new Uint8Array(value));
-      } else if (value instanceof Uint8Array) {
-        buffer.writeSync(value);
-      } else if (!value) {
-        // noop for undefined
-      } else {
-        throw new Error("unhandled type on stream read");
-      }
-    }
-
-    return buffer.bytes().buffer;
-  }
-
-  /**
-   * @param {Exclude<BodyInit, ReadableStream> | null} bodySource 
-   */
-  function bodyToArrayBuffer(bodySource) {
-    if (isTypedArray(bodySource)) {
-      return bodySource.buffer;
-    } else if (bodySource instanceof ArrayBuffer) {
-      return bodySource;
-    } else if (typeof bodySource === "string") {
-      const enc = new TextEncoder();
-      return enc.encode(bodySource).buffer;
-    } else if (
-      bodySource instanceof FormData ||
-      bodySource instanceof URLSearchParams
-    ) {
-      const enc = new TextEncoder();
-      return enc.encode(bodySource.toString()).buffer;
-    } else if (!bodySource) {
-      return new ArrayBuffer(0);
-    }
-    throw new Error(
-      `Body type not implemented: ${bodySource.constructor.name}`,
-    );
-  }
-
-  const BodyUsedError =
-    "Failed to execute 'clone' on 'Body': body is already used";
-
-  const teeBody = Symbol("Body#tee");
-
-  // fastBody and dontValidateUrl allow users to opt out of certain behaviors
-  const fastBody = Symbol("Body#fast");
-  const dontValidateUrl = Symbol("dontValidateUrl");
-  const lazyHeaders = Symbol("lazyHeaders");
-
-  class Body {
-    #contentType = "";
-    #size;
-    /** @type {BodyInit | null} */
-    #bodySource;
-    /** @type {ReadableStream<Uint8Array> | null} */
-    #stream = null;
-
-    /**
-     * @param {BodyInit| null} bodySource 
-     * @param {{contentType: string, size?: number}} meta 
-     */
-    constructor(bodySource, meta) {
-      validateBodyType(this.constructor.name, bodySource);
-      this.#bodySource = bodySource;
-      this.#contentType = meta.contentType;
-      this.#size = meta.size;
-    }
-
-    get body() {
-      if (!this.#stream) {
-        if (!this.#bodySource) {
-          return null;
-        } else if (this.#bodySource instanceof ReadableStream) {
-          this.#stream = this.#bodySource;
-        } else {
-          const buf = bodyToArrayBuffer(this.#bodySource);
-          if (!(buf instanceof ArrayBuffer)) {
-            throw new Error(
-              `Expected ArrayBuffer from body`,
-            );
-          }
-
-          this.#stream = new ReadableStream({
-            /**
-             * @param {ReadableStreamDefaultController<Uint8Array>} controller 
-             */
-            start(controller) {
-              controller.enqueue(new Uint8Array(buf));
-              controller.close();
-            },
-          });
-        }
-      }
-
-      return this.#stream;
-    }
-
-    // Optimization that allows caller to bypass expensive ReadableStream.
-    [fastBody]() {
-      if (!this.#bodySource) {
-        return null;
-      } else if (!(this.#bodySource instanceof ReadableStream)) {
-        return bodyToArrayBuffer(this.#bodySource);
-      } else {
-        return this.body;
-      }
-    }
-
-    /** @returns {BodyInit | null} */
-    [teeBody]() {
-      if (this.#stream || this.#bodySource instanceof ReadableStream) {
-        const body = this.body;
-        if (body) {
-          const [stream1, stream2] = body.tee();
-          this.#stream = stream1;
-          return stream2;
-        } else {
-          return null;
-        }
-      }
-
-      return this.#bodySource;
-    }
-
-    get bodyUsed() {
-      if (this.body && isReadableStreamDisturbed(this.body)) {
-        return true;
-      }
-      return false;
-    }
-
-    set bodyUsed(_) {
-      // this is a noop per spec
-    }
-
-    /** @returns {Promise<Blob>} */
-    async blob() {
-      return new Blob([await this.arrayBuffer()], {
-        type: this.#contentType,
-      });
-    }
-
-    // ref: https://fetch.spec.whatwg.org/#body-mixin
-    /** @returns {Promise<FormData>} */
-    async formData() {
-      const formData = new FormData();
-      const mimeType = parseMimeType(this.#contentType);
-      if (mimeType) {
-        if (mimeType.type === "multipart" && mimeType.subtype === "form-data") {
-          // ref: https://tools.ietf.org/html/rfc2046#section-5.1
-          const boundary = mimeType.parameters.get("boundary");
-          const body = new Uint8Array(await this.arrayBuffer());
-          return parseFormData(body, boundary);
-        } else if (
-          mimeType.type === "application" &&
-          mimeType.subtype === "x-www-form-urlencoded"
-        ) {
-          // From https://github.com/github/fetch/blob/master/fetch.js
-          // Copyright (c) 2014-2016 GitHub, Inc. MIT License
-          const body = await this.text();
-          try {
-            body
-              .trim()
-              .split("&")
-              .forEach((bytes) => {
-                if (bytes) {
-                  const split = bytes.split("=");
-                  if (split.length >= 2) {
-                    // @ts-expect-error this is safe because of the above check
-                    const name = split.shift().replace(/\+/g, " ");
-                    const value = split.join("=").replace(/\+/g, " ");
-                    formData.append(
-                      decodeURIComponent(name),
-                      decodeURIComponent(value),
-                    );
-                  }
-                }
-              });
-          } catch (e) {
-            throw new TypeError("Invalid form urlencoded format");
-          }
-          return formData;
-        }
-      }
-
-      throw new TypeError("Invalid form data");
-    }
-
-    /** @returns {Promise<string>} */
-    async text() {
-      if (typeof this.#bodySource === "string") {
-        return this.#bodySource;
-      }
-
-      const ab = await this.arrayBuffer();
-      const decoder = new TextDecoder("utf-8");
-      return decoder.decode(ab);
-    }
-
-    /** @returns {Promise<any>} */
-    async json() {
-      const raw = await this.text();
-      return JSON.parse(raw);
-    }
-
-    /** @returns {Promise<ArrayBuffer>} */
-    arrayBuffer() {
-      if (this.#bodySource instanceof ReadableStream) {
-        const body = this.body;
-        if (!body) throw new TypeError("Unreachable state (no body)");
-        return bufferFromStream(body.getReader(), this.#size);
-      }
-      return Promise.resolve(bodyToArrayBuffer(this.#bodySource));
-    }
-  }
+  const webidl = window.__bootstrap.webidl;
+  const { byteLowerCase } = window.__bootstrap.infra;
+  const { InnerBody, extractBody } = window.__bootstrap.fetchBody;
+  const {
+    toInnerRequest,
+    fromInnerResponse,
+    redirectStatus,
+    nullBodyStatus,
+    networkError,
+  } = window.__bootstrap.fetch;
+
+  const REQUEST_BODY_HEADER_NAMES = [
+    "content-encoding",
+    "content-language",
+    "content-location",
+    "content-type",
+  ];
 
   /**
-   * @param {Deno.CreateHttpClientOptions} options
-   * @returns {HttpClient}
-   */
-  function createHttpClient(options) {
-    return new HttpClient(core.opSync("op_create_http_client", options));
-  }
-
-  class HttpClient {
-    /**
-     * @param {number} rid 
-     */
-    constructor(rid) {
-      this.rid = rid;
-    }
-    close() {
-      core.close(this.rid);
-    }
-  }
-
-  /**
-   * @param {{ headers: [string,string][], method: string, url: string, baseUrl: string | null, clientRid: number | null, hasBody: boolean }} args 
+   * @param {{ method: string, url: string, headers: [string, string][], clientRid: number | null, hasBody: boolean }} args 
    * @param {Uint8Array | null} body 
-   * @returns {{requestRid: number, requestBodyRid: number | null}}
+   * @returns {{ requestRid: number, requestBodyRid: number | null }}
    */
   function opFetch(args, body) {
-    let zeroCopy;
-    if (body != null) {
-      zeroCopy = new Uint8Array(body.buffer, body.byteOffset, body.byteLength);
-    }
-    return core.opSync("op_fetch", args, zeroCopy);
+    return core.opSync("op_fetch", args, body);
   }
 
   /**
-   * @param {number} rid
-   * @returns {Promise<{status: number, statusText: string, headers: Record<string,string[]>, url: string, responseRid: number}>}
+   * @param {number} rid 
+   * @returns {Promise<{ status: number, statusText: string, headers: [string, string][], url: string, responseRid: number }>}
    */
   function opFetchSend(rid) {
     return core.opAsync("op_fetch_send", rid);
@@ -515,631 +54,254 @@
    * @returns {Promise<void>}
    */
   function opFetchRequestWrite(rid, body) {
-    const zeroCopy = new Uint8Array(
-      body.buffer,
-      body.byteOffset,
-      body.byteLength,
-    );
-    return core.opAsync("op_fetch_request_write", rid, zeroCopy);
+    return core.opAsync("op_fetch_request_write", rid, body);
   }
 
-  const NULL_BODY_STATUS = [101, 204, 205, 304];
-  const REDIRECT_STATUS = [301, 302, 303, 307, 308];
-
   /**
-   * @param {string} s
-   * @returns {string}
+   * @param {number} rid 
+   * @param {Uint8Array} body 
+   * @returns {Promise<number>}
    */
-  function byteUpperCase(s) {
-    return String(s).replace(/[a-z]/g, function byteUpperCaseReplace(c) {
-      return c.toUpperCase();
-    });
+  function opFetchResponseRead(rid, body) {
+    return core.opAsync("op_fetch_response_read", rid, body);
   }
 
   /**
-   * @param {string} m
-   * @returns {boolean}
+   * @param {number} responseBodyRid
+   * @returns {ReadableStream<Uint8Array>}
    */
-  function isKnownMethod(m) {
-    return (
-      m === "DELETE" ||
-      m === "GET" ||
-      m === "HEAD" ||
-      m === "OPTIONS" ||
-      m === "POST" ||
-      m === "PUT"
-    );
+  function createResponseBodyStream(responseBodyRid) {
+    return new ReadableStream({
+      type: "bytes",
+      async pull(controller) {
+        try {
+          // This is the largest possible size for a single packet on a TLS
+          // stream.
+          const chunk = new Uint8Array(16 * 1024 + 256);
+          const read = await opFetchResponseRead(
+            responseBodyRid,
+            chunk,
+          );
+          if (read > 0) {
+            // We read some data. Enqueue it onto the stream.
+            controller.enqueue(chunk.subarray(0, read));
+          } else {
+            // We have reached the end of the body, so we close the stream.
+            controller.close();
+            core.close(responseBodyRid);
+          }
+        } catch (err) {
+          // There was an error while reading a chunk of the body, so we
+          // error.
+          controller.error(err);
+          controller.close();
+          core.close(responseBodyRid);
+        }
+      },
+      cancel() {
+        core.close(responseBodyRid);
+      },
+    });
   }
 
   /**
-   * @param {string} m
-   * @returns {string}
+   * @param {InnerRequest} req 
+   * @param {boolean} recursive
+   * @returns {Promise<InnerResponse>}
    */
-  function normalizeMethod(m) {
-    // Fast path for already valid methods
-    if (isKnownMethod(m)) {
-      return m;
-    }
-    // Normalize lower case (slowpath and should be avoided ...)
-    const u = byteUpperCase(m);
-    if (isKnownMethod(u)) {
-      return u;
-    }
-    // Otherwise passthrough
-    return m;
-  }
-
-  class Request extends Body {
-    /** @type {string} */
-    #method = "GET";
-    /** @type {string} */
-    #url = "";
-    /** @type {Headers | string[][]} */
-    #headers;
-    /** @type {"include" | "omit" | "same-origin" | undefined} */
-    #credentials = "omit";
-
-    /**
-     * @param {RequestInfo} input 
-     * @param {RequestInit} init 
-     */
-    // @ts-expect-error because the use of super in this constructor is valid.
-    constructor(input, init) {
-      if (arguments.length < 1) {
-        throw TypeError("Not enough arguments");
-      }
-
-      if (!init) {
-        init = {};
-      }
-
-      let b;
-
-      // prefer body from init
-      if (init.body) {
-        b = init.body;
-      } else if (input instanceof Request) {
-        if (input.bodyUsed) {
-          throw TypeError(BodyUsedError);
-        }
-        b = input[teeBody]();
-      } else if (typeof input === "object" && "body" in input && input.body) {
-        if (input.bodyUsed) {
-          throw TypeError(BodyUsedError);
-        }
-        b = input.body;
-      } else {
-        b = "";
-      }
-
-      let headers;
-      let contentType = "";
-      // prefer headers from init
-      if (init.headers) {
-        if (init[lazyHeaders] && Array.isArray(init.headers)) {
-          // Trust the headers are valid, and only put them into the `Headers`
-          // strucutre when the user accesses the property. We also assume that
-          // all passed headers are lower-case (as is the case when they come
-          // from hyper in Rust), and that headers are of type
-          // `[string, string][]`.
-          headers = init.headers;
-          for (const tuple of headers) {
-            if (tuple[0] === "content-type") {
-              contentType = tuple[1];
-            }
-          }
+  async function mainFetch(req, recursive) {
+    /** @type {ReadableStream<Uint8Array> | Uint8Array | null} */
+    let reqBody = null;
+    if (req.body !== null) {
+      if (req.body.streamOrStatic instanceof ReadableStream) {
+        if (req.body.length === null) {
+          reqBody = req.body.stream;
         } else {
-          headers = new Headers(init.headers);
-          contentType = headers.get("content-type") || "";
+          const reader = req.body.stream.getReader();
+          const r1 = await reader.read();
+          if (r1.done) throw new TypeError("Unreachable");
+          reqBody = r1.value;
+          const r2 = await reader.read();
+          if (!r2.done) throw new TypeError("Unreachable");
         }
-      } else if (input instanceof Request) {
-        headers = input.headers;
-        contentType = headers.get("content-type") || "";
       } else {
-        headers = new Headers();
-      }
-
-      super(b, { contentType });
-      this.#headers = headers;
-
-      if (input instanceof Request) {
-        if (input.bodyUsed) {
-          throw TypeError(BodyUsedError);
-        }
-        // headers are already set above. no reason to do it again
-        this.#method = input.method;
-        this.#url = input.url;
-        this.#credentials = input.credentials;
-      } else {
-        // Constructing a URL just for validation is known to be expensive.
-        // dontValidateUrl allows one to opt out.
-        if (init[dontValidateUrl]) {
-          this.#url = input;
-        } else {
-          const baseUrl = getLocationHref();
-          this.#url = baseUrl != null
-            ? new URL(String(input), baseUrl).href
-            : new URL(String(input)).href;
-        }
-      }
-
-      if (init && "method" in init && init.method) {
-        this.#method = normalizeMethod(init.method);
-      }
-
-      if (
-        init &&
-        "credentials" in init &&
-        init.credentials &&
-        ["omit", "same-origin", "include"].indexOf(init.credentials) !== -1
-      ) {
-        this.credentials = init.credentials;
-      }
-    }
-
-    clone() {
-      if (this.bodyUsed) {
-        throw TypeError(BodyUsedError);
-      }
-
-      const iterators = this.headers.entries();
-      const headersList = [];
-      for (const header of iterators) {
-        headersList.push(header);
-      }
-
-      const body = this[teeBody]();
-
-      return new Request(this.url, {
-        body,
-        method: this.method,
-        headers: new Headers(headersList),
-        credentials: this.credentials,
-      });
-    }
-
-    get method() {
-      return this.#method;
-    }
-
-    set method(_) {
-      // can not set method
-    }
-
-    get url() {
-      return this.#url;
-    }
-
-    set url(_) {
-      // can not set url
-    }
-
-    get headers() {
-      if (!(this.#headers instanceof Headers)) {
-        this.#headers = new Headers(this.#headers);
-      }
-      return this.#headers;
-    }
-
-    set headers(_) {
-      // can not set headers
-    }
-
-    get credentials() {
-      return this.#credentials;
-    }
-
-    set credentials(_) {
-      // can not set credentials
-    }
-  }
-
-  const responseData = new WeakMap();
-  class Response extends Body {
-    /** 
-     * @param {BodyInit | null} body 
-     * @param {ResponseInit} [init]
-     */
-    constructor(body = null, init) {
-      init = init ?? {};
-
-      if (typeof init !== "object") {
-        throw new TypeError(`'init' is not an object`);
-      }
-
-      const extraInit = responseData.get(init) || {};
-      let { type = "default", url = "" } = extraInit;
-
-      let status = init.status === undefined ? 200 : Number(init.status || 0);
-      let statusText = init.statusText ?? "";
-      let headers = init.headers instanceof Headers
-        ? init.headers
-        : new Headers(init.headers);
-
-      if (init.status !== undefined && (status < 200 || status > 599)) {
-        throw new RangeError(
-          `The status provided (${init.status}) is outside the range [200, 599]`,
-        );
-      }
-
-      // null body status
-      if (body && NULL_BODY_STATUS.includes(status)) {
-        throw new TypeError("Response with null body status cannot have body");
-      }
-
-      if (!type) {
-        type = "default";
-      } else {
-        if (type == "error") {
-          // spec: https://fetch.spec.whatwg.org/#concept-network-error
-          status = 0;
-          statusText = "";
-          headers = new Headers();
-          body = null;
-          /* spec for other Response types:
-           https://fetch.spec.whatwg.org/#concept-filtered-response-basic
-           Please note that type "basic" is not the same thing as "default".*/
-        } else if (type == "basic") {
-          for (const h of headers) {
-            /* Forbidden Response-Header Names:
-             https://fetch.spec.whatwg.org/#forbidden-response-header-name */
-            if (["set-cookie", "set-cookie2"].includes(h[0].toLowerCase())) {
-              headers.delete(h[0]);
-            }
+        req.body.streamOrStatic.consumed = true;
+        reqBody = req.body.streamOrStatic.body;
+      }
+    }
+
+    const { requestRid, requestBodyRid } = opFetch({
+      method: req.method,
+      url: req.currentUrl(),
+      headers: req.headerList,
+      clientRid: req.clientRid,
+      hasBody: reqBody !== null,
+    }, reqBody instanceof Uint8Array ? reqBody : null);
+
+    if (requestBodyRid !== null) {
+      if (reqBody === null || !(reqBody instanceof ReadableStream)) {
+        throw new TypeError("Unreachable");
+      }
+      const reader = reqBody.getReader();
+      (async () => {
+        while (true) {
+          const { value, done } = await reader.read();
+          if (done) break;
+          if (!(value instanceof Uint8Array)) {
+            await reader.cancel("value not a Uint8Array");
+            break;
           }
-        } else if (type == "cors") {
-          /* CORS-safelisted Response-Header Names:
-             https://fetch.spec.whatwg.org/#cors-safelisted-response-header-name */
-          const allowedHeaders = [
-            "Cache-Control",
-            "Content-Language",
-            "Content-Length",
-            "Content-Type",
-            "Expires",
-            "Last-Modified",
-            "Pragma",
-          ].map((c) => c.toLowerCase());
-          for (const h of headers) {
-            /* Technically this is still not standards compliant because we are
-             supposed to allow headers allowed in the
-             'Access-Control-Expose-Headers' header in the 'internal response'
-             However, this implementation of response doesn't seem to have an
-             easy way to access the internal response, so we ignore that
-             header.
-             TODO(serverhiccups): change how internal responses are handled
-             so we can do this properly. */
-            if (!allowedHeaders.includes(h[0].toLowerCase())) {
-              headers.delete(h[0]);
-            }
+          try {
+            await opFetchRequestWrite(requestBodyRid, value);
+          } catch (err) {
+            await reader.cancel(err);
+            break;
           }
-          /* TODO(serverhiccups): Once I fix the 'internal response' thing,
-           these actually need to treat the internal response differently */
-        } else if (type == "opaque" || type == "opaqueredirect") {
-          url = "";
-          status = 0;
-          statusText = "";
-          headers = new Headers();
-          body = null;
         }
-      }
-
-      const contentType = headers.get("content-type") || "";
-      const size = Number(headers.get("content-length")) || undefined;
-
-      super(body, { contentType, size });
-
-      this.url = url;
-      this.statusText = statusText;
-      this.status = extraInit.status || status;
-      this.headers = headers;
-      this.redirected = extraInit.redirected || false;
-      this.type = type;
-    }
-
-    get ok() {
-      return 200 <= this.status && this.status < 300;
+        core.close(requestBodyRid);
+      })();
+    }
+
+    const resp = await opFetchSend(requestRid);
+    /** @type {InnerResponse} */
+    const response = {
+      headerList: resp.headers,
+      status: resp.status,
+      body: null,
+      statusMessage: resp.statusText,
+      type: "basic",
+      url() {
+        if (this.urlList.length == 0) return null;
+        return this.urlList[this.urlList.length - 1];
+      },
+      urlList: req.urlList,
+    };
+    if (redirectStatus(resp.status)) {
+      switch (req.redirectMode) {
+        case "error":
+          core.close(resp.responseRid);
+          return networkError(
+            "Encountered redirect while redirect mode is set to 'error'",
+          );
+        case "follow":
+          core.close(resp.responseRid);
+          return httpRedirectFetch(req, response);
+        case "manual":
+          break;
+      }
+    }
+
+    if (nullBodyStatus(response.status)) {
+      core.close(resp.responseRid);
+    } else {
+      response.body = new InnerBody(createResponseBodyStream(resp.responseRid));
     }
 
-    clone() {
-      if (this.bodyUsed) {
-        throw TypeError(BodyUsedError);
-      }
-
-      const iterators = this.headers.entries();
-      const headersList = [];
-      for (const header of iterators) {
-        headersList.push(header);
-      }
-
-      const body = this[teeBody]();
+    if (recursive) return response;
 
-      return new Response(body, {
-        status: this.status,
-        statusText: this.statusText,
-        headers: new Headers(headersList),
-      });
+    if (response.urlList.length === 0) {
+      response.urlList = [...req.urlList];
     }
 
-    /**
-     * @param {string } url 
-     * @param {number} status
-     */
-    static redirect(url, status = 302) {
-      if (![301, 302, 303, 307, 308].includes(status)) {
-        throw new RangeError(
-          "The redirection status must be one of 301, 302, 303, 307 and 308.",
-        );
-      }
-      return new Response(null, {
-        status,
-        statusText: "",
-        headers: [["Location", String(url)]],
-      });
-    }
-  }
-
-  /** @type {string | null} */
-  let baseUrl = null;
-
-  /** @param {string} href */
-  function setBaseUrl(href) {
-    baseUrl = href;
+    return response;
   }
 
   /**
-   * @param {string} url 
-   * @param {string} method 
-   * @param {Headers} headers 
-   * @param {ReadableStream<Uint8Array> | ArrayBufferView | undefined} body 
-   * @param {number | null} clientRid
-   * @returns {Promise<{status: number, statusText: string, headers: Record<string,string[]>, url: string, responseRid: number}>}
+   * @param {InnerRequest} request
+   * @param {InnerResponse} response
+   * @returns {Promise<InnerResponse>}
    */
-  async function sendFetchReq(url, method, headers, body, clientRid) {
-    /** @type {[string, string][]} */
-    let headerArray = [];
-    if (headers) {
-      headerArray = Array.from(headers.entries());
+  function httpRedirectFetch(request, response) {
+    const locationHeaders = response.headerList.filter((entry) =>
+      byteLowerCase(entry[0]) === "location"
+    );
+    if (locationHeaders.length === 0) {
+      return response;
     }
-
-    const { requestRid, requestBodyRid } = opFetch(
-      {
-        method,
-        url,
-        baseUrl,
-        headers: headerArray,
-        clientRid,
-        hasBody: !!body,
-      },
-      body instanceof Uint8Array ? body : null,
+    const locationURL = new URL(
+      locationHeaders[0][1],
+      response.url() ?? undefined,
     );
-    if (requestBodyRid) {
-      if (!(body instanceof ReadableStream)) {
-        throw new TypeError("Unreachable state (body is not ReadableStream).");
+    if (locationURL.hash === "") {
+      locationURL.hash = request.currentUrl().hash;
+    }
+    if (locationURL.protocol !== "https:" && locationURL.protocol !== "http:") {
+      return networkError("Can not redirect to a non HTTP(s) url");
+    }
+    if (request.redirectCount === 20) {
+      return networkError("Maximum number of redirects (20) reached");
+    }
+    request.redirectCount++;
+    if (
+      response.status !== 303 && request.body !== null &&
+      request.body.source === null
+    ) {
+      return networkError(
+        "Can not redeliver a streaming request body after a redirect",
+      );
+    }
+    if (
+      ((response.status === 301 || response.status === 302) &&
+        request.method === "POST") ||
+      (response.status === 303 &&
+        (request.method !== "GET" && request.method !== "HEAD"))
+    ) {
+      request.method = "GET";
+      request.body = null;
+      for (let i = 0; i < request.headerList.length; i++) {
+        if (
+          REQUEST_BODY_HEADER_NAMES.includes(
+            byteLowerCase(request.headerList[i][0]),
+          )
+        ) {
+          request.headerList.splice(i, 1);
+          i--;
+        }
       }
-      const writer = new WritableStream({
-        /**
-         * @param {Uint8Array} chunk 
-         * @param {WritableStreamDefaultController} controller 
-         */
-        async write(chunk, controller) {
-          try {
-            await opFetchRequestWrite(requestBodyRid, chunk);
-          } catch (err) {
-            controller.error(err);
-          }
-        },
-        close() {
-          core.close(requestBodyRid);
-        },
-      });
-      body.pipeTo(writer);
     }
-
-    return await opFetchSend(requestRid);
+    if (request.body !== null) {
+      const res = extractBody(request.body.source);
+      request.body = res.body;
+    }
+    request.urlList.push(locationURL.href);
+    return mainFetch(request, true);
   }
 
   /**
-   * @param {Request | URL | string} input 
-   * @param {RequestInit & {client: Deno.HttpClient}} [init] 
-   * @returns {Promise<Response>}
+   * @param {RequestInfo} input 
+   * @param {RequestInit} init 
    */
-  async function fetch(input, init) {
-    /** @type {string | null} */
-    let url;
-    let method = null;
-    let headers = null;
-    let body;
-    let clientRid = null;
-    let redirected = false;
-    let remRedirectCount = 20; // TODO(bartlomieju): use a better way to handle
-
-    if (typeof input === "string" || input instanceof URL) {
-      url = typeof input === "string" ? input : input.href;
-      if (init != null) {
-        method = init.method || null;
-        if (init.headers) {
-          headers = init.headers instanceof Headers
-            ? init.headers
-            : new Headers(init.headers);
-        } else {
-          headers = null;
-        }
-
-        // ref: https://fetch.spec.whatwg.org/#body-mixin
-        // Body should have been a mixin
-        // but we are treating it as a separate class
-        if (init.body) {
-          if (!headers) {
-            headers = new Headers();
-          }
-          let contentType = "";
-          if (typeof init.body === "string") {
-            body = new TextEncoder().encode(init.body);
-            contentType = "text/plain;charset=UTF-8";
-          } else if (isTypedArray(init.body)) {
-            body = init.body;
-          } else if (init.body instanceof ArrayBuffer) {
-            body = new Uint8Array(init.body);
-          } else if (init.body instanceof URLSearchParams) {
-            body = new TextEncoder().encode(init.body.toString());
-            contentType = "application/x-www-form-urlencoded;charset=UTF-8";
-          } else if (init.body instanceof Blob) {
-            body = init.body[_byteSequence];
-            contentType = init.body.type;
-          } else if (init.body instanceof FormData) {
-            const res = encodeFormData(init.body);
-            body = res.body;
-            contentType = res.contentType;
-          } else if (init.body instanceof ReadableStream) {
-            body = init.body;
-          }
-          if (contentType && !headers.has("content-type")) {
-            headers.set("content-type", contentType);
-          }
-        }
-
-        if (init.client instanceof HttpClient) {
-          clientRid = init.client.rid;
-        }
-      }
-    } else {
-      url = input.url;
-      method = input.method;
-      headers = input.headers;
+  async function fetch(input, init = {}) {
+    const prefix = "Failed to call 'fetch'";
+    input = webidl.converters["RequestInfo"](input, {
+      prefix,
+      context: "Argument 1",
+    });
+    init = webidl.converters["RequestInit"](init, {
+      prefix,
+      context: "Argument 2",
+    });
 
-      if (input.body) {
-        body = input.body;
-      }
+    // 1.
+    const requestObject = new Request(input, init);
+    // 2.
+    const request = toInnerRequest(requestObject);
+    // 10.
+    if (!requestObject.headers.has("Accept")) {
+      request.headerList.push(["Accept", "*/*"]);
     }
 
-    let responseBody;
-    let responseInit = {};
-    while (remRedirectCount) {
-      const fetchResp = await sendFetchReq(
-        url,
-        method ?? "GET",
-        headers ?? new Headers(),
-        body,
-        clientRid,
+    // 12.
+    const response = await mainFetch(request, false);
+    if (response.type === "error") {
+      throw new TypeError(
+        "Fetch failed: " + (response.error ?? "unknown error"),
       );
-      const rid = fetchResp.responseRid;
-
-      if (
-        NULL_BODY_STATUS.includes(fetchResp.status) ||
-        REDIRECT_STATUS.includes(fetchResp.status)
-      ) {
-        // We won't use body of received response, so close it now
-        // otherwise it will be kept in resource table.
-        core.close(rid);
-        responseBody = null;
-      } else {
-        responseBody = new ReadableStream({
-          type: "bytes",
-          /** @param {ReadableStreamDefaultController<Uint8Array>} controller */
-          async pull(controller) {
-            try {
-              const chunk = new Uint8Array(16 * 1024 + 256);
-              const read = await core.opAsync(
-                "op_fetch_response_read",
-                rid,
-                chunk,
-              );
-              if (read != 0) {
-                if (chunk.length == read) {
-                  controller.enqueue(chunk);
-                } else {
-                  controller.enqueue(chunk.subarray(0, read));
-                }
-              } else {
-                controller.close();
-                core.close(rid);
-              }
-            } catch (e) {
-              controller.error(e);
-              controller.close();
-              core.close(rid);
-            }
-          },
-          cancel() {
-            // When reader.cancel() is called
-            core.close(rid);
-          },
-        });
-      }
-
-      responseInit = {
-        status: 200,
-        statusText: fetchResp.statusText,
-        headers: fetchResp.headers,
-      };
-
-      responseData.set(responseInit, {
-        redirected,
-        rid: fetchResp.responseRid,
-        status: fetchResp.status,
-        url: fetchResp.url,
-      });
-
-      const response = new Response(responseBody, responseInit);
-
-      if (REDIRECT_STATUS.includes(fetchResp.status)) {
-        // We're in a redirect status
-        switch ((init && init.redirect) || "follow") {
-          case "error":
-            responseInit = {};
-            responseData.set(responseInit, {
-              type: "error",
-              redirected: false,
-              url: "",
-            });
-            return new Response(null, responseInit);
-          case "manual":
-            // On the web this would return a `opaqueredirect` response, but
-            // those don't make sense server side. See denoland/deno#8351.
-            return response;
-          case "follow":
-          // fallthrough
-          default: {
-            /** @type {string | null} */
-            let redirectUrl = response.headers.get("Location");
-            if (redirectUrl == null) {
-              return response; // Unspecified
-            }
-            if (
-              !redirectUrl.startsWith("http://") &&
-              !redirectUrl.startsWith("https://")
-            ) {
-              redirectUrl = new URL(redirectUrl, fetchResp.url).href;
-            }
-            url = redirectUrl;
-            redirected = true;
-            remRedirectCount--;
-          }
-        }
-      } else {
-        return response;
-      }
     }
 
-    responseData.set(responseInit, {
-      type: "error",
-      redirected: false,
-      url: "",
-    });
-
-    return new Response(null, responseInit);
+    return fromInnerResponse(response, "immutable");
   }
 
-  window.__bootstrap.fetch = {
-    FormData,
-    setBaseUrl,
-    fetch,
-    Request,
-    Response,
-    HttpClient,
-    createHttpClient,
-    fastBody,
-    dontValidateUrl,
-    lazyHeaders,
-  };
+  window.__bootstrap.fetch ??= {};
+  window.__bootstrap.fetch.fetch = fetch;
 })(this);