Only emit a warning on duplicate request headers (#1972)

* only emit a warning on duplicate request headers

* use debug instead of warn

* Remove left over console and enforce with eslint

.eslintrc.yml

@@ -29,6 +29,7 @@ rules:
 
   # Nock additions.
   strict: ['error', 'safe']
+  no-console: 'error'
   no-loop-func: 'error'
   no-var: 'error'
   prefer-const: 'error'

lib/common.js

@@ -194,7 +194,7 @@ function isJSONContent(headers) {
  *
  * Duplicates throw an error.
  */
-function headersFieldNamesToLowerCase(headers) {
+function headersFieldNamesToLowerCase(headers, throwOnDuplicate) {
   if (!isPlainObject(headers)) {
     throw Error('Headers must be provided as an object')
   }
@@ -203,9 +203,15 @@ function headersFieldNamesToLowerCase(headers) {
   Object.entries(headers).forEach(([fieldName, fieldValue]) => {
     const key = fieldName.toLowerCase()
     if (lowerCaseHeaders[key] !== undefined) {
-      throw Error(
-        `Failed to convert header keys to lower case due to field name conflict: ${key}`
-      )
+      if (throwOnDuplicate) {
+        throw Error(
+          `Failed to convert header keys to lower case due to field name conflict: ${key}`
+        )
+      } else {
+        debug(
+          `Duplicate header provided in request: ${key}. Only the last value can be matched.`
+        )
+      }
     }
     lowerCaseHeaders[key] = fieldValue
   })

lib/intercepted_request_router.js

@@ -40,7 +40,10 @@ class InterceptedRequestRouter {
       // affecting the user so we use a clone of the object.
       ...options,
       // We use lower-case header field names throughout Nock.
-      headers: common.headersFieldNamesToLowerCase(options.headers || {}),
+      headers: common.headersFieldNamesToLowerCase(
+        options.headers || {},
+        false
+      ),
     }
     this.interceptors = interceptors
 

lib/interceptor.js

@@ -66,7 +66,8 @@ module.exports = class Interceptor {
 
     //  We use lower-case header field names throughout Nock.
     this.reqheaders = common.headersFieldNamesToLowerCase(
-      scope.scopeOptions.reqheaders || {}
+      scope.scopeOptions.reqheaders || {},
+      true
     )
     this.badheaders = common.headersFieldsArrayToLowerCase(
       scope.scopeOptions.badheaders || []

lib/recorder.js

@@ -168,7 +168,7 @@ let currentRecordingId = 0
 const defaultRecordOptions = {
   dont_print: false,
   enable_reqheaders_recording: false,
-  logging: console.log,
+  logging: console.log, // eslint-disable-line no-console
   output_objects: false,
   use_separator: true,
 }

tests/test_common.js

@@ -155,7 +155,7 @@ describe('`headersFieldNamesToLowerCase()`', () => {
       'Content-typE': 'plain/text',
     }
     const inputClone = { ...input }
-    const result = common.headersFieldNamesToLowerCase(input)
+    const result = common.headersFieldNamesToLowerCase(input, true)
     const expected = {
       host: 'example.test',
       'content-type': 'plain/text',
@@ -167,10 +167,13 @@ describe('`headersFieldNamesToLowerCase()`', () => {
 
   it('throws on conflicting keys', () => {
     expect(() =>
-      common.headersFieldNamesToLowerCase({
-        HoSt: 'example.test',
-        HOST: 'example.test',
-      })
+      common.headersFieldNamesToLowerCase(
+        {
+          HoSt: 'example.test',
+          HOST: 'example.test',
+        },
+        true
+      )
     ).to.throw(
       'Failed to convert header keys to lower case due to field name conflict: host'
     )

tests/test_header_matching.js

@@ -425,6 +425,31 @@ describe('Header matching', () => {
       scope.done()
     })
 
+    it('should only match the last duplicate request header', done => {
+      const scope = nock('http://example.test', {
+        reqheaders: {
+          'x-auth-token': 'biz',
+        },
+      })
+        .get('/')
+        .reply()
+
+      // Can't use Got here because it would change these headers
+      const req = http.get('http://example.test', {
+        headers: {
+          'x-auth-token': 'foo',
+          'X-Auth-Token': 'bar',
+          'X-AUTH-TOKEN': 'biz',
+        },
+      })
+
+      req.on('response', res => {
+        expect(res.statusCode).to.equal(200)
+        scope.done()
+        done()
+      })
+    })
+
     // https://github.com/nock/nock/issues/966
     it('mocking succeeds when mocked and specified request headers have falsy values', async () => {
       const scope = nock('http://example.test', {