fix: never prepend subject to message text when bot receives it

src/mimeparser.rs

@@ -662,6 +662,7 @@ impl MimeMessage {
             self.squash_attachment_parts();
         }
 
+        if !context.get_config_bool(Config::Bot).await? {
             if let Some(ref subject) = self.get_subject() {
                 let mut prepend_subject = true;
                 if !self.decrypting_failed {
@@ -691,6 +692,7 @@ impl MimeMessage {
                     }
                 }
             }
+        }
 
         if self.is_forwarded {
             for part in &mut self.parts {
@@ -3933,4 +3935,31 @@ Content-Disposition: reaction\n\
 
         Ok(())
     }
+
+    /// Tests that subject is not prepended to the message
+    /// when bot receives it.
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_bot_no_subject() {
+        let context = TestContext::new().await;
+        context.set_config(Config::Bot, Some("1")).await.unwrap();
+        let raw = br#"Message-ID: <foobar@example.org>
+From: foo <foo@example.org>
+Subject: Some subject
+To: bar@example.org
+MIME-Version: 1.0
+Content-Type: text/plain; charset=utf-8
+
+/help
+"#;
+
+        let message = MimeMessage::from_bytes(&context.ctx, &raw[..], None)
+            .await
+            .unwrap();
+        assert_eq!(message.get_subject(), Some("Some subject".to_string()));
+
+        assert_eq!(message.parts.len(), 1);
+        assert_eq!(message.parts[0].typ, Viewtype::Text);
+        // Not "Some subject – /help"
+        assert_eq!(message.parts[0].msg, "/help");
+    }
 }