melib/imap/cache: return NotFound on cache miss

Set error kind to NotFound instead of Bug, since it is possible a
mailbox state is not cached. Also add convenience function
ignore_not_found() that converts NotFound Err Results to Ok(()).

Signed-off-by: Manos Pitsidianakis <manos@pitsidianak.is>

melib/src/imap/cache.rs

@@ -59,6 +59,15 @@ pub struct CachedEnvelope {
     pub modsequence: Option<ModSequence>,
 }
 
+/// Helper function for ignoring cache misses with
+/// `.or_else(ignore_not_found)?`.
+pub fn ignore_not_found(err: Error) -> Result<()> {
+    if matches!(err.kind, ErrorKind::NotFound) {
+        return Ok(());
+    }
+    Err(err)
+}
+
 pub trait ImapCache: Send + std::fmt::Debug {
     fn reset(&mut self) -> Result<()>;
     fn mailbox_state(&mut self, mailbox_hash: MailboxHash) -> Result<Option<()>>;

melib/src/imap/cache/sqlite3_cache.rs

@@ -421,7 +421,7 @@ impl ImapCache for Sqlite3Cache {
             .cloned()
             .unwrap_or_default();
         if self.mailbox_state(mailbox_hash)?.is_none() {
-            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::Bug));
+            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::NotFound));
         }
         let Self {
             ref mut connection,
@@ -479,7 +479,7 @@ impl ImapCache for Sqlite3Cache {
         flags: SmallVec<[FlagOp; 8]>,
     ) -> Result<()> {
         if self.mailbox_state(mailbox_hash)?.is_none() {
-            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::Bug));
+            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::NotFound));
         }
         let Self {
             ref mut connection,
@@ -537,7 +537,7 @@ impl ImapCache for Sqlite3Cache {
         refresh_events: &[(UID, RefreshEvent)],
     ) -> Result<()> {
         if self.mailbox_state(mailbox_hash)?.is_none() {
-            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::Bug));
+            return Err(Error::new("Mailbox is not in cache").set_kind(ErrorKind::NotFound));
         }
         {
             let Self {

melib/src/imap/watch.rs

@@ -23,7 +23,7 @@ use std::sync::Arc;
 use imap_codec::imap_types::search::SearchKey;
 
 use super::*;
-use crate::backends::SpecialUsageMailbox;
+use crate::{backends::SpecialUsageMailbox, imap::cache::ignore_not_found};
 
 /// Arguments for IMAP watching functions
 pub struct ImapWatchKit {
@@ -91,7 +91,9 @@ pub async fn idle(kit: ImapWatchKit) -> Result<()> {
         if let Some(v) = uidvalidities.get(&mailbox_hash) {
             if *v != select_response.uidvalidity {
                 if let Ok(Some(mut cache_handle)) = uid_store.cache_handle() {
-                    cache_handle.clear(mailbox_hash, &select_response)?;
+                    cache_handle
+                        .clear(mailbox_hash, &select_response)
+                        .or_else(ignore_not_found)?;
                 }
                 conn.add_refresh_event(RefreshEvent {
                     account_hash: uid_store.account_hash,
@@ -221,7 +223,9 @@ pub async fn examine_updates(
             if let Some(v) = uidvalidities.get(&mailbox_hash) {
                 if *v != select_response.uidvalidity {
                     if let Ok(Some(mut cache_handle)) = cache_handle {
-                        cache_handle.clear(mailbox_hash, &select_response)?;
+                        cache_handle
+                            .clear(mailbox_hash, &select_response)
+                            .or_else(ignore_not_found)?;
                     }
                     conn.add_refresh_event(RefreshEvent {
                         account_hash: uid_store.account_hash,
@@ -372,16 +376,15 @@ pub async fn examine_updates(
             }
         }
         if let Ok(Some(mut cache_handle)) = cache_handle {
-            if cache_handle.mailbox_state(mailbox_hash)?.is_some() {
-                cache_handle
-                    .insert_envelopes(mailbox_hash, &v)
-                    .chain_err_summary(|| {
-                        format!(
-                            "Could not save envelopes in cache for mailbox {}",
-                            mailbox.imap_path()
-                        )
-                    })?;
-            }
+            cache_handle
+                .insert_envelopes(mailbox_hash, &v)
+                .or_else(ignore_not_found)
+                .chain_err_summary(|| {
+                    format!(
+                        "Could not save envelopes in cache for mailbox {}",
+                        mailbox.imap_path()
+                    )
+                })?;
         }
 
         for FetchResponse { uid, envelope, .. } in v {