melib: add supports_search() method to MailBackend

melib/src/backends.rs

@@ -287,6 +287,7 @@ pub type ResultFuture<T> = Result<Pin<Box<dyn Future<Output = Result<T>> + Send
 pub trait MailBackend: ::std::fmt::Debug + Send + Sync {
     fn is_async(&self) -> bool;
     fn is_remote(&self) -> bool;
+    fn supports_search(&self) -> bool;
     fn is_online(&self) -> Result<()> {
         Err(MeliError::new("Unimplemented."))
     }

melib/src/backends/imap.rs

@@ -183,6 +183,11 @@ impl MailBackend for ImapType {
     fn is_remote(&self) -> bool {
         true
     }
+
+    fn supports_search(&self) -> bool {
+        true
+    }
+
     fn get_async(
         &mut self,
         mailbox: &Mailbox,

melib/src/backends/jmap.rs

@@ -198,6 +198,10 @@ impl MailBackend for JmapType {
         true
     }
 
+    fn supports_search(&self) -> bool {
+        true
+    }
+
     fn is_online(&self) -> Result<()> {
         if self.online.lock().unwrap().1.is_err()
             && Instant::now().duration_since(self.online.lock().unwrap().0)

melib/src/backends/maildir/backend.rs

@@ -183,6 +183,10 @@ impl MailBackend for MaildirType {
         false
     }
 
+    fn supports_search(&self) -> bool {
+        false
+    }
+
     fn is_online(&self) -> Result<()> {
         Ok(())
     }

melib/src/backends/mbox.rs

@@ -710,6 +710,10 @@ impl MailBackend for MboxType {
         false
     }
 
+    fn supports_search(&self) -> bool {
+        false
+    }
+
     fn is_online(&self) -> Result<()> {
         Ok(())
     }

melib/src/backends/notmuch.rs

@@ -326,6 +326,10 @@ impl MailBackend for NotmuchDb {
         false
     }
 
+    fn supports_search(&self) -> bool {
+        true
+    }
+
     fn is_online(&self) -> Result<()> {
         Ok(())
     }

src/plugins/backend.rs

@@ -75,6 +75,11 @@ impl MailBackend for PluginBackend {
         false
     }
 
+    fn supports_search(&self) -> bool {
+        // TODO
+        false
+    }
+
     fn is_online(&self) -> Result<()> {
         if let Ok(mut is_online) = self.is_online.try_lock() {
             let now = std::time::Instant::now();