feat: add developer option to disable IDLE

deltachat-ffi/deltachat.h

@@ -492,6 +492,9 @@ char*           dc_get_blobdir               (const dc_context_t* context);
  * - `fetch_existing_msgs` = 1=fetch most recent existing messages on configure (default),
  *                    0=do not fetch existing messages on configure.
  *                    In both cases, existing recipients are added to the contact database.
+ * - `disable_idle` = 1=disable IMAP IDLE even if the server supports it,
+ *                    0=use IMAP IDLE if the server supports it.
+ *                    This is a developer option used for testing polling used as an IDLE fallback.
  * - `download_limit` = Messages up to this number of bytes are downloaded automatically.
  *                    For larger messages, only the header is downloaded and a placeholder is shown.
  *                    These messages can be downloaded fully using dc_download_full_msg() later.

src/config.rs

@@ -286,6 +286,12 @@ pub enum Config {
     #[strum(props(default = "60"))]
     ScanAllFoldersDebounceSecs,
 
+    /// Whether to avoid using IMAP IDLE even if the server supports it.
+    ///
+    /// This is a developer option for testing "fake idle".
+    #[strum(props(default = "0"))]
+    DisableIdle,
+
     /// Defines the max. size (in bytes) of messages downloaded automatically.
     /// 0 = no limit.
     #[strum(props(default = "0"))]
@@ -479,7 +485,8 @@ impl Context {
             | Config::Bot
             | Config::NotifyAboutWrongPw
             | Config::SendSyncMsgs
-            | Config::SignUnencrypted => {
+            | Config::SignUnencrypted
+            | Config::DisableIdle => {
                 ensure!(
                     matches!(value, None | Some("0") | Some("1")),
                     "Boolean value must be either 0 or 1"

src/context.rs

@@ -579,6 +579,7 @@ impl Context {
         let mdns_enabled = self.get_config_int(Config::MdnsEnabled).await?;
         let bcc_self = self.get_config_int(Config::BccSelf).await?;
         let send_sync_msgs = self.get_config_int(Config::SendSyncMsgs).await?;
+        let disable_idle = self.get_config_bool(Config::DisableIdle).await?;
 
         let prv_key_cnt = self.sql.count("SELECT COUNT(*) FROM keypairs;", ()).await?;
 
@@ -691,6 +692,7 @@ impl Context {
         );
         res.insert("bcc_self", bcc_self.to_string());
         res.insert("send_sync_msgs", send_sync_msgs.to_string());
+        res.insert("disable_idle", disable_idle.to_string());
         res.insert("private_key_count", prv_key_cnt.to_string());
         res.insert("public_key_count", pub_key_cnt.to_string());
         res.insert("fingerprint", fingerprint_str);

src/imap/idle.rs

@@ -7,7 +7,9 @@ use futures_lite::FutureExt;
 
 use super::session::Session;
 use super::Imap;
+use crate::config::Config;
 use crate::imap::{client::IMAP_TIMEOUT, FolderMeaning};
+use crate::log::LogExt;
 use crate::{context::Context, scheduler::InterruptInfo};
 
 const IDLE_TIMEOUT: Duration = Duration::from_secs(23 * 60);
@@ -21,6 +23,10 @@ impl Session {
     ) -> Result<(Self, InterruptInfo)> {
         use futures::future::FutureExt;
 
+        if context.get_config_bool(Config::DisableIdle).await? {
+            bail!("IMAP IDLE is disabled");
+        }
+
         if !self.can_idle() {
             bail!("IMAP server does not have IDLE capability");
         }
@@ -163,7 +169,14 @@ impl Imap {
                         continue;
                     }
                     if let Some(session) = &self.session {
-                        if session.can_idle() {
+                        if session.can_idle()
+                            && !context
+                                .get_config_bool(Config::DisableIdle)
+                                .await
+                                .context("Failed to get disable_idle config")
+                                .log_err(context)
+                                .unwrap_or_default()
+                        {
                             // we only fake-idled because network was gone during IDLE, probably
                             break InterruptInfo::new(false);
                         }

src/scheduler.rs

@@ -574,6 +574,19 @@ async fn fetch_idle(
                 .await;
         }
 
+        if ctx
+            .get_config_bool(Config::DisableIdle)
+            .await
+            .context("Failed to get disable_idle config")
+            .log_err(ctx)
+            .unwrap_or_default()
+        {
+            info!(ctx, "IMAP IDLE is disabled, going to fake idle.");
+            return connection
+                .fake_idle(ctx, Some(watch_folder), folder_meaning)
+                .await;
+        }
+
         info!(ctx, "IMAP session supports IDLE, using it.");
         match session
             .idle(