fetch: improve output for FormData, Response, Request

lib/web/fetch/formdata.js

@@ -154,6 +154,15 @@ class FormData {
       this[kState].push(entry)
     }
   }
+
+  toString () {
+    let output = 'FormData:\n'
+    this[kState].forEach(entry => {
+      output += `${entry.name}: ${entry.value}\n`
+    })
+
+    return output
+  }
 }
 
 iteratorMixin('FormData', FormData, kState, 'name', 'value')

lib/web/fetch/response.js

@@ -3,6 +3,7 @@
 const { Headers, HeadersList, fill } = require('./headers')
 const { extractBody, cloneBody, mixinBody } = require('./body')
 const util = require('../../core/util')
+const nodeUtil = require('util')
 const { kEnumerableProperty } = util
 const {
   isValidReasonPhrase,
@@ -252,6 +253,13 @@ class Response {
     // clonedResponse, this’s headers’s guard, and this’s relevant Realm.
     return fromInnerResponse(clonedResponse, this[kHeaders][kGuard], this[kRealm])
   }
+
+  [nodeUtil.inspect.custom] (depth, options) {
+    const { status, statusText, headersList } = this[kState]
+    const headersString = nodeUtil.inspect(headersList)
+
+    return `Response { status: ${status}, statusText: "${statusText}", headers: ${headersString} }`
+  }
 }
 
 mixinBody(Response)

test/fetch/formdata-inspect-custom.js

@@ -0,0 +1,15 @@
+'use strict'
+
+const { FormData } = require('../../')
+const { test } = require('node:test')
+const assert = require('node:assert')
+
+test('FormData class custom inspection', () => {
+  const formData = new FormData()
+  formData.append('username', 'john_doe')
+  formData.append('email', 'john@example.com')
+
+  const expectedOutput = 'FormData:\nusername: john_doe\nemail: john@example.com\n'
+
+  assert.strictEqual(formData.toString(), expectedOutput)
+})

test/fetch/response-inspect-custom.js

@@ -0,0 +1,19 @@
+'use strict'
+
+const { describe, it } = require('node:test')
+const assert = require('assert')
+const util = require('util')
+const { Response } = require('../../')
+
+describe('Response custom inspection', () => {
+  it('should return a custom inspect output', () => {
+    const response = new Response(null)
+    const inspectedOutput = util.inspect(response)
+    const expectedOutput = `Response { status: 200, statusText: "", headers: HeadersList {
+  cookies: null,
+  [Symbol(headers map)]: Map(0) {},
+  [Symbol(headers map sorted)]: null
+} }`
+    assert.strictEqual(inspectedOutput, expectedOutput)
+  })
+})