fetch: replace Proxy objects

lib/fetch/headers.js

@@ -2,6 +2,7 @@
 
 'use strict'
 
+const assert = require('assert')
 const { validateHeaderName, validateHeaderValue } = require('http')
 const { kHeadersList } = require('../core/symbols')
 const { kGuard } = require('./symbols')
@@ -149,6 +150,60 @@ class HeadersList extends Array {
   }
 }
 
+class FilteredHeadersList extends HeadersList {
+  /** @type {(name: string) => boolean} */
+  filter = () => true;
+
+  /**
+   * @param {HeadersList} headersList
+   * @param {typeof this['filter'] | undefined} filter
+   */
+  constructor (headersList, filter) {
+    super()
+    this.push(...headersList) // copy values
+
+    if (filter) {
+      this.filter = filter
+    }
+  }
+
+  /**
+   * @param  {never[]} args
+   */
+  slice (...args) {
+    assert(args.length === 0)
+    const arr = []
+    for (let index = 0; index < this.length; index += 2) {
+      if (this.filter(this[index])) {
+        arr.push(this[index], this[index + 1])
+      }
+    }
+    return arr
+  }
+
+  /**
+   * @param {string} name
+   */
+  get (name) {
+    if (this.filter(name)) {
+      return super.get(name)
+    } else {
+      return undefined
+    }
+  }
+
+  /**
+   * @param {string} name
+   */
+  has (name) {
+    if (this.filter(name)) {
+      return super.has(name)
+    } else {
+      return undefined
+    }
+  }
+}
+
 class Headers {
   constructor (...args) {
     if (
@@ -385,6 +440,7 @@ module.exports = {
   Headers,
   HeadersList,
   binarySearch,
+  FilteredHeadersList,
   normalizeAndValidateHeaderName,
   normalizeAndValidateHeaderValue
 }

lib/fetch/response.js

@@ -1,6 +1,6 @@
 'use strict'
 
-const { Headers, HeadersList, fill } = require('./headers')
+const { Headers, HeadersList, fill, FilteredHeadersList } = require('./headers')
 const { AbortError } = require('../core/errors')
 const { extractBody, cloneBody, mixinBody } = require('./body')
 const util = require('../core/util')
@@ -371,45 +371,14 @@ function makeNetworkError (reason) {
 }
 
 function makeFilteredResponse (response, state) {
-  state = {
-    internalResponse: response,
-    ...state
-  }
-
-  return new Proxy(response, {
-    get (target, p) {
-      return p in state ? state[p] : target[p]
-    },
-    set (target, p, value) {
-      assert(!(p in state))
-      target[p] = value
-      return true
-    }
-  })
-}
-
-function makeFilteredHeadersList (headersList, filter) {
-  return new Proxy(headersList, {
-    get (target, prop) {
-      // Override methods used by Headers class.
-      if (prop === 'get' || prop === 'has') {
-        return (name) => filter(name) ? target[prop](name) : undefined
-      } else if (prop === 'slice') {
-        return (...args) => {
-          assert(args.length === 0)
-          const arr = []
-          for (let index = 0; index < target.length; index += 2) {
-            if (filter(target[index])) {
-              arr.push(target[index], target[index + 1])
-            }
-          }
-          return arr
-        }
-      } else {
-        return target[prop]
-      }
-    }
-  })
+  // https://fetch.spec.whatwg.org/#concept-filtered-response
+  // A filtered response has a corresponding internalResponse, which is its
+  // response. However, a key accessed in the response object must also be
+  // available in its internal response (and vice versa).
+  const cloned = cloneResponse(response)
+  Object.assign(response, { internalResponse: cloned }, state)
+
+  return response
 }
 
 // https://fetch.spec.whatwg.org/#concept-filtered-response
@@ -423,7 +392,10 @@ function filterResponse (response, type) {
 
     return makeFilteredResponse(response, {
       type: 'basic',
-      headersList: makeFilteredHeadersList(response.headersList, (name) => !forbiddenResponseHeaderNames.includes(name))
+      headersList: new FilteredHeadersList(
+        response.headersList,
+        (name) => !forbiddenResponseHeaderNames.includes(name)
+      )
     })
   } else if (type === 'cors') {
     // A CORS filtered response is a filtered response whose type is "cors"
@@ -433,7 +405,10 @@ function filterResponse (response, type) {
 
     return makeFilteredResponse(response, {
       type: 'cors',
-      headersList: makeFilteredHeadersList(response.headersList, (name) => !corsSafeListedResponseHeaderNames.includes(name))
+      headersList: new FilteredHeadersList(
+        response.headersList,
+        (name) => !corsSafeListedResponseHeaderNames.includes(name)
+      )
     })
   } else if (type === 'opaque') {
     // An opaque filtered response is a filtered response whose type is
@@ -456,7 +431,7 @@ function filterResponse (response, type) {
       type: 'opaqueredirect',
       status: 0,
       statusText: '',
-      headersList: makeFilteredHeadersList(response.headersList, () => false),
+      headersList: new FilteredHeadersList([], () => false),
       body: null
     })
   } else {

package.json

@@ -66,6 +66,7 @@
     "@sinonjs/fake-timers": "^7.0.5",
     "@types/node": "^16.9.1",
     "abort-controller": "^3.0.0",
+    "babel-eslint": "^10.1.0",
     "busboy": "^0.3.1",
     "chai": "^4.3.4",
     "chai-as-promised": "^7.1.1",
@@ -103,7 +104,8 @@
     "ignore": [
       "lib/llhttp/constants.js",
       "lib/llhttp/utils.js"
-    ]
+    ],
+    "parser": "babel-eslint"
   },
   "tsd": {
     "directory": "test/types",