From f46cdc065b371f0361527c46b30320a4572425eb Mon Sep 17 00:00:00 2001
From: Yamagishi Kazutoshi <ykzts@desire.sh>
Date: Fri, 31 Jul 2020 07:55:43 +0900
Subject: [PATCH] fix(xmlhttprequest): throw exception when invalid state
 (#123)

---
 src/xmlhttprequest.ts              | 37 +++++++++++++++++++++++++++---
 test/integration/xmlhttprequest.ts | 19 ++++++++++++++-
 2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/src/xmlhttprequest.ts b/src/xmlhttprequest.ts
index 7ad47d1..68f6bc0 100644
--- a/src/xmlhttprequest.ts
+++ b/src/xmlhttprequest.ts
@@ -147,7 +147,11 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget {
   }
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  get response(): any {
+  get response(): ArrayBufferLike | Buffer | string | any | null {
+    if (this.readyState !== XMLHttpRequest.DONE) {
+      return null;
+    }
+
     switch (this.responseType) {
       case 'arraybuffer':
         return new Uint8Array(this.#responseBuffer).buffer;
@@ -156,14 +160,32 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget {
       case 'document':
         return this.responseXML;
       case 'json':
-        // eslint-disable-next-line @typescript-eslint/no-unsafe-return
-        return JSON.parse(this.responseText);
+        try {
+          const text = this.#responseBuffer.toString();
+
+          // eslint-disable-next-line @typescript-eslint/no-unsafe-return
+          return JSON.parse(text);
+        } catch {
+          return null;
+        }
       default:
         return this.responseText;
     }
   }
 
   get responseText(): string {
+    if (this.responseType !== '' && this.responseType !== 'text') {
+      // TODO: Add human readable message.
+      throw new DOMException('', 'InvalidStateError');
+    }
+
+    if (
+      this.readyState !== XMLHttpRequest.LOADING &&
+      this.readyState !== XMLHttpRequest.DONE
+    ) {
+      return '';
+    }
+
     return this.#responseBuffer.toString();
   }
 
@@ -190,6 +212,15 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget {
   }
 
   get responseXML(): null {
+    if (this.responseType !== '' && this.responseType !== 'document') {
+      // TODO: Add human readable message.
+      throw new DOMException('', 'InvalidStateError');
+    }
+
+    if (this.readyState !== XMLHttpRequest.DONE) {
+      return null;
+    }
+
     return null;
   }
 
diff --git a/test/integration/xmlhttprequest.ts b/test/integration/xmlhttprequest.ts
index c196e1c..fca3154 100644
--- a/test/integration/xmlhttprequest.ts
+++ b/test/integration/xmlhttprequest.ts
@@ -241,7 +241,7 @@ describe('XMLHttpRequest', () => {
     });
   });
 
-  describe('.responseText', () => {
+  describe('.response', () => {
     it('returns object when given JSON', (done) => {
       const client = new XMLHttpRequest();
 
@@ -261,6 +261,23 @@ describe('XMLHttpRequest', () => {
       client.responseType = 'json';
       client.send(null);
     });
+
+    it('returns null when given invalid JSON', (done) => {
+      const client = new XMLHttpRequest();
+
+      client.addEventListener('load', () => {
+        expect(client.response).toBe(null);
+
+        done();
+      });
+
+      client.open(
+        'GET',
+        `${baseURL}/?body=%7B%22test%22%3A%22value%22&type=application/json`
+      );
+      client.responseType = 'json';
+      client.send(null);
+    });
   });
 
   describe('.withCredentials', () => {