fetch: set referrer properly (nodejs#2125)

* fetch: set referrer properly

Fixes nodejs#2124

* fix: origin is not a url

lib/fetch/request.js

@@ -232,14 +232,18 @@ class Request {
         }
 
         // 3. If one of the following is true
-        // parsedReferrer’s cannot-be-a-base-URL is true, scheme is "about",
-        // and path contains a single string "client"
-        // parsedReferrer’s origin is not same origin with origin
+        // - parsedReferrer’s scheme is "about" and path is the string "client"
+        // - parsedReferrer’s origin is not same origin with origin
         // then set request’s referrer to "client".
-        // TODO
-
-        // 4. Otherwise, set request’s referrer to parsedReferrer.
-        request.referrer = parsedReferrer
+        if (
+          (parsedReferrer.protocol === 'about:' && parsedReferrer.hostname === 'client') ||
+          (origin && !sameOrigin(parsedReferrer, this[kRealm].settingsObject.baseUrl))
+        ) {
+          request.referrer = 'client'
+        } else {
+          // 4. Otherwise, set request’s referrer to parsedReferrer.
+          request.referrer = parsedReferrer
+        }
       }
     }
 

test/fetch/request.js

@@ -476,4 +476,15 @@ test('set-cookie headers get cleared when passing a Request as first param', (t)
   t.end()
 })
 
+// https://github.com/nodejs/undici/issues/2124
+test('request.referrer', (t) => {
+  for (const referrer of ['about://client', 'about://client:1234']) {
+    const request = new Request('http://a', { referrer })
+
+    t.equal(request.referrer, 'about:client')
+  }
+
+  t.end()
+})
+
 teardown(() => process.exit())