notmuch: update the count whenever the database is updated

Specifically, this re-runs the count command whenever the databased lock
is released. This event is triggered whenever the database is closed
after it was opened for writing, but NOT when it was opened for reading.

Author: Stebalien

NEWS.md

@@ -1,3 +1,9 @@
+#  i3status-rust 0.35.0 [unreleased]
+
+### Breaking Changes
+
+- The `interval` option has been removed from the `notmuch` block in favor of watching the notmuch database for changes.
+
 # i3status-rust 0.34.0
 
 ### New Blocks and Features

src/blocks/notmuch.rs

@@ -43,14 +43,16 @@
 //! # Icons Used
 //! - `mail`
 
+use std::path::Path;
+
+use inotify::{Inotify, WatchMask};
+
 use super::prelude::*;
 
 #[derive(Deserialize, Debug, SmartDefault)]
 #[serde(deny_unknown_fields, default)]
 pub struct Config {
     pub format: FormatConfig,
-    #[default(10.into())]
-    pub interval: Seconds,
     #[default("~/.mail".into())]
     pub maildir: ShellString,
     pub query: String,
@@ -68,7 +70,21 @@ pub async fn run(config: &Config, api: &CommonApi) -> Result<()> {
     let format = config.format.with_default(" $icon $count ")?;
 
     let db = config.maildir.expand()?;
-    let mut timer = config.interval.timer();
+    let notify = Inotify::init().error("Failed to start inotify")?;
+
+    for lockpath in ["xapian/flintlock", ".notmuch/xapian/flintlock"] {
+        let fname = Path::new(&*db).join(lockpath);
+        if fname.exists() {
+            notify
+                .watches()
+                .add(fname, WatchMask::CLOSE_WRITE)
+                .error("failed to add inotify watch")?;
+        }
+    }
+
+    let mut updates = notify
+        .into_event_stream([0; 1024])
+        .error("Failed to create event stream")?;
 
     loop {
         // TODO: spawn_blocking?
@@ -96,7 +112,7 @@ pub async fn run(config: &Config, api: &CommonApi) -> Result<()> {
         api.set_widget(widget)?;
 
         tokio::select! {
-            _ = timer.tick() => (),
+            _ = updates.next_debounced() => (),
             _ = api.wait_for_update_request() => (),
         }
     }