fix: do not treat utf8 requests as binary

packages/driver/README.md

@@ -27,8 +27,6 @@ You can also run all of the driver's tests locally. We don't really recommend th
 It's usually easier to run the tests in the GUI, commit, and then see if anything broke elsewhere.
 
 ```bash
-yarn workspace @packages/driver start
-
 # in separate terminal
 yarn workspace @packages/driver cypress:run
 

packages/net-stubbing/lib/server/middleware/request.ts

@@ -2,7 +2,6 @@ import _ from 'lodash'
 import { concatStream } from '@packages/network'
 import Debug from 'debug'
 import url from 'url'
-import { getEncoding } from 'istextorbinary'
 
 import {
   RequestMiddleware,
@@ -16,6 +15,7 @@ import {
   sendStaticResponse,
   setDefaultHeaders,
   mergeDeletedHeaders,
+  getBodyEncoding,
 } from '../util'
 import { InterceptedRequest } from '../intercepted-request'
 import { BackendRoute } from '../types'
@@ -118,7 +118,13 @@ export const InterceptRequest: RequestMiddleware = async function () {
     throw new Error('req.body must be a string or a Buffer')
   }
 
-  if (getEncoding(req.body) !== 'binary') {
+  const encoding = getBodyEncoding(req)
+
+  debug('req.body encoding', encoding)
+
+  // leave the requests that send a binary buffer unchanged
+  // but we can work with the "normal" string requests
+  if (encoding !== 'binary') {
     req.body = req.body.toString('utf8')
   }
 

packages/net-stubbing/lib/server/util.ts

@@ -20,6 +20,7 @@ import { InterceptedRequest } from './intercepted-request'
 // TODO: move this into net-stubbing once cy.route is removed
 import { parseContentType } from '@packages/server/lib/controllers/xhrs'
 import { CyHttpMessages } from '../external-types'
+import { getEncoding } from 'istextorbinary'
 
 const debug = Debug('cypress:net-stubbing:server:util')
 
@@ -208,3 +209,22 @@ export function mergeDeletedHeaders (before: CyHttpMessages.BaseMessage, after:
     !after.headers[k] && delete before.headers[k]
   }
 }
+
+type BodyEncoding = 'utf8' | 'binary' | null
+
+export function getBodyEncoding (req: CyHttpMessages.IncomingRequest): BodyEncoding {
+  if (!req.body) {
+    return null
+  }
+
+  // a simple heuristic for detecting UTF8 encoded requests
+  if (req.headers && req.headers['content-type']) {
+    if (req.headers['content-type'].includes('charset=UTF-8')) {
+      return 'utf8'
+    }
+  }
+
+  // with fallback to inspecting the buffer using
+  // https://github.com/bevry/istextorbinary
+  return getEncoding(req.body)
+}

packages/server/test/e2e/7_issue_15901_spec.js

@@ -0,0 +1,14 @@
+const e2e = require('../support/helpers/e2e').default
+const Fixtures = require('../support/helpers/fixtures')
+
+// https://github.com/cypress-io/cypress/issues/15901
+describe('issue 15901', () => {
+  e2e.setup()
+
+  it('does not crash', function () {
+    return e2e.exec(this, {
+      project: Fixtures.projectPath('issue-15901'),
+      expectedExitCode: 0,
+    })
+  })
+})

packages/server/test/support/fixtures/projects/issue-15901/cypress.json

@@ -0,0 +1,6 @@
+{
+  "fixturesFolder": false,
+  "supportFile": false,
+  "pluginsFile": false,
+  "video": false
+}

packages/server/test/support/fixtures/projects/issue-15901/cypress/integration/spec.js

@@ -0,0 +1,5 @@
+// @see https://github.com/cypress-io/cypress/issues/15901
+it('does not crash', () => {
+  cy.intercept('POST', 'http://localhost:5000/api/sample')
+  cy.visit('index.html')
+})

packages/server/test/support/fixtures/projects/issue-15901/index.html

@@ -0,0 +1,16 @@
+<script>
+  // the actual server response does not matter
+  // just trying to verify the network layer does not crash
+  // https://github.com/cypress-io/cypress/issues/15901
+  fetch('http://localhost:5000/api/sample', {
+    method: 'POST',
+    body: JSON.stringify({
+      // does not crash
+      // first: 'hello'
+      // crash
+      first: '東京都新東東'
+    })
+  }).catch(r => {
+    console.log(r)
+  })
+</script>