Only notify once for each app update (#762)

src/main.rs

@@ -379,7 +379,7 @@ fn inner_main() -> Result<ExitCode> {
         // Check for updates if we're in a non-silent log level.
         #[cfg(feature = "update-informer")]
         if !is_stdin && log_level >= LogLevel::Default && atty::is(atty::Stream::Stdout) {
-            updates::check_for_updates();
+            let _ = updates::check_for_updates();
         }
 
         if messages.iter().any(|message| !message.fixed) && !cli.exit_zero {

src/updates.rs

@@ -1,19 +1,65 @@
+use std::fs::{create_dir_all, read_to_string, File};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+use anyhow::Result;
 use colored::Colorize;
 
 const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
 const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
 
-pub fn check_for_updates() {
+fn cache_dir() -> &'static str {
+    "./.ruff_cache"
+}
+
+fn file_path() -> PathBuf {
+    Path::new(cache_dir()).join(".update-informer")
+}
+
+/// Get the "latest" version for which the user has been informed.
+fn get_latest() -> Result<Option<String>> {
+    let path = file_path();
+    if path.exists() {
+        Ok(Some(read_to_string(path)?.trim().to_string()))
+    } else {
+        Ok(None)
+    }
+}
+
+/// Set the "latest" version for which the user has been informed.
+fn set_latest(version: &str) -> Result<()> {
+    create_dir_all(cache_dir())?;
+    let path = file_path();
+    let mut file = File::create(path)?;
+    file.write_all(version.trim().as_bytes())
+        .map_err(|e| e.into())
+}
+
+/// Update the user if a newer version is available.
+pub fn check_for_updates() -> Result<()> {
     use update_informer::{registry, Check};
 
     let informer = update_informer::new(registry::PyPI, CARGO_PKG_NAME, CARGO_PKG_VERSION);
 
-    if let Some(new_version) = informer.check_version().ok().flatten() {
+    if let Some(new_version) = informer
+        .check_version()
+        .ok()
+        .flatten()
+        .map(|version| version.to_string())
+    {
+        // If we've already notified the user about this version, return early.
+        if let Some(latest_version) = get_latest()? {
+            if latest_version == new_version {
+                return Ok(());
+            }
+        }
+        set_latest(&new_version)?;
+
         let msg = format!(
             "A new version of {pkg_name} is available: v{pkg_version} -> {new_version}",
             pkg_name = CARGO_PKG_NAME.italic().cyan(),
             pkg_version = CARGO_PKG_VERSION,
-            new_version = new_version.to_string().green()
+            new_version = new_version.green()
         );
 
         let cmd = format!(
@@ -24,4 +70,6 @@ pub fn check_for_updates() {
 
         println!("\n{msg}\n{cmd}");
     }
+
+    Ok(())
 }