Emit events from account manager

Errors and warnings are emitted with a special 0 account ID.

deltachat-ffi/deltachat.h

@@ -4993,7 +4993,7 @@ char* dc_event_get_data2_str(dc_event_t* event);
  *
  * @memberof dc_event_t
  * @param event Event object as returned from dc_accounts_get_next_event().
- * @return account-id belonging to the event or 0 for errors.
+ * @return account-id belonging to the event, 0 for account manager errors.
  */
 uint32_t dc_event_get_account_id(dc_event_t* event);
 

deltachat-ffi/src/lib.rs

@@ -3856,9 +3856,19 @@ pub unsafe extern "C" fn dc_accounts_select_account(
     }
 
     let accounts = &*accounts;
-    block_on(async move { accounts.write().await.select_account(id).await })
-        .map(|_| 1)
-        .unwrap_or(0)
+    block_on(async move {
+        let mut accounts = accounts.write().await;
+        match accounts.select_account(id).await {
+            Ok(()) => 1,
+            Err(err) => {
+                accounts.emit_event(EventType::Error(format!(
+                    "Failed to select account: {:#}",
+                    err
+                )));
+                0
+            }
+        }
+    })
 }
 
 #[no_mangle]
@@ -3870,7 +3880,19 @@ pub unsafe extern "C" fn dc_accounts_add_account(accounts: *mut dc_accounts_t) -
 
     let accounts = &mut *accounts;
 
-    block_on(async move { accounts.write().await.add_account().await }).unwrap_or(0)
+    block_on(async move {
+        let mut accounts = accounts.write().await;
+        match accounts.add_account().await {
+            Ok(id) => id,
+            Err(err) => {
+                accounts.emit_event(EventType::Error(format!(
+                    "Failed to add account: {:#}",
+                    err
+                )));
+                0
+            }
+        }
+    })
 }
 
 #[no_mangle]
@@ -3885,9 +3907,19 @@ pub unsafe extern "C" fn dc_accounts_remove_account(
 
     let accounts = &mut *accounts;
 
-    block_on(async move { accounts.write().await.remove_account(id).await })
-        .map(|_| 1)
-        .unwrap_or_else(|_| 0)
+    block_on(async move {
+        let mut accounts = accounts.write().await;
+        match accounts.remove_account(id).await {
+            Ok(()) => 1,
+            Err(err) => {
+                accounts.emit_event(EventType::Error(format!(
+                    "Failed to remove account: {:#}",
+                    err
+                )));
+                0
+            }
+        }
+    })
 }
 
 #[no_mangle]
@@ -3904,14 +3936,21 @@ pub unsafe extern "C" fn dc_accounts_migrate_account(
     let dbfile = to_string_lossy(dbfile);
 
     block_on(async move {
-        accounts
-            .write()
-            .await
+        let mut accounts = accounts.write().await;
+        match accounts
             .migrate_account(async_std::path::PathBuf::from(dbfile))
             .await
+        {
+            Ok(id) => id,
+            Err(err) => {
+                accounts.emit_event(EventType::Error(format!(
+                    "Failed to migrate account: {:#}",
+                    err
+                )));
+                0
+            }
+        }
     })
-    .map(|_| 1)
-    .unwrap_or_else(|_| 0)
 }
 
 #[no_mangle]

src/accounts.rs

@@ -13,7 +13,7 @@ use anyhow::{ensure, Context as _, Result};
 use serde::{Deserialize, Serialize};
 
 use crate::context::Context;
-use crate::events::Event;
+use crate::events::{Event, EventType, Events};
 
 /// Account manager, that can handle multiple accounts in a single place.
 #[derive(Debug)]
@@ -23,12 +23,8 @@ pub struct Accounts {
     accounts: BTreeMap<u32, Context>,
     emitter: EventEmitter,
 
-    /// Sender side of the fake event channel.
-    ///
-    /// We never send any events over this channel, but hold it during the account manager lifetime
-    /// to prevent `EventEmitter` from returning `None` as long as account manager is alive, even if
-    /// it holds no accounts which could emit events.
-    fake_sender: Sender<crate::events::Event>,
+    /// Event channel to emit account manager errors.
+    events: Events,
 }
 
 impl Accounts {
@@ -65,9 +61,9 @@ impl Accounts {
 
         let emitter = EventEmitter::new();
 
-        // Fake event stream to prevent event emitter from closing.
-        let (fake_sender, fake_receiver) = channel::bounded(1);
-        emitter.sender.send(fake_receiver).await?;
+        let events = Events::default();
+
+        emitter.sender.send(events.get_emitter()).await?;
 
         for account in accounts.values() {
             emitter.add_account(account).await?;
@@ -78,7 +74,7 @@ impl Accounts {
             config,
             accounts,
             emitter,
-            fake_sender,
+            events,
         })
     }
 
@@ -262,6 +258,11 @@ impl Accounts {
         }
     }
 
+    /// Emits a single event.
+    pub fn emit_event(&self, event: EventType) {
+        self.events.emit(Event { id: 0, typ: event })
+    }
+
     /// Returns unified event emitter.
     pub async fn get_event_emitter(&self) -> EventEmitter {
         self.emitter.clone()
@@ -272,13 +273,13 @@ impl Accounts {
 #[derive(Debug, Clone)]
 pub struct EventEmitter {
     /// Aggregate stream of events from all accounts.
-    stream: Arc<RwLock<futures::stream::SelectAll<Receiver<crate::events::Event>>>>,
+    stream: Arc<RwLock<futures::stream::SelectAll<crate::events::EventEmitter>>>,
 
     /// Sender for the channel where new account emitters will be pushed.
-    sender: Sender<Receiver<crate::events::Event>>,
+    sender: Sender<crate::events::EventEmitter>,
 
     /// Receiver for the channel where new account emitters will be pushed.
-    receiver: Receiver<Receiver<crate::events::Event>>,
+    receiver: Receiver<crate::events::EventEmitter>,
 }
 
 impl EventEmitter {
@@ -311,9 +312,7 @@ impl EventEmitter {
 
     /// Add event emitter of a new account to the aggregate event emitter.
     pub async fn add_account(&self, context: &Context) -> Result<()> {
-        self.sender
-            .send(context.get_event_emitter().into_inner())
-            .await?;
+        self.sender.send(context.get_event_emitter()).await?;
         Ok(())
     }
 }

src/events.rs

@@ -62,10 +62,6 @@ impl Events {
 pub struct EventEmitter(Receiver<Event>);
 
 impl EventEmitter {
-    pub(crate) fn into_inner(self) -> Receiver<Event> {
-        self.0
-    }
-
     /// Blocking recv of an event. Return `None` if the `Sender` has been droped.
     pub fn recv_sync(&self) -> Option<Event> {
         async_std::task::block_on(self.recv())