feat: add taskbar progress reporting

src/cargo/core/compiler/job_queue/mod.rs

@@ -854,7 +854,7 @@ impl<'gctx> DrainState<'gctx> {
     }
 
     fn handle_error(
-        &self,
+        &mut self,
         shell: &mut Shell,
         err_state: &mut ErrorsDuringDrain,
         new_err: impl Into<ErrorToHandle>,
@@ -863,6 +863,7 @@ impl<'gctx> DrainState<'gctx> {
         if new_err.print_always || err_state.count == 0 {
             crate::display_error(&new_err.error, shell);
             if err_state.count == 0 && !self.active.is_empty() {
+                self.progress.indicate_error();
                 let _ = shell.warn("build failed, waiting for other jobs to finish...");
             }
             err_state.count += 1;

src/cargo/core/shell.rs

@@ -56,6 +56,7 @@ impl Shell {
                 stderr_tty: std::io::stderr().is_terminal(),
                 stdout_unicode: supports_unicode(&std::io::stdout()),
                 stderr_unicode: supports_unicode(&std::io::stderr()),
+                progress_report: supports_progress_report(),
             },
             verbosity: Verbosity::Verbose,
             needs_clear: false,
@@ -286,6 +287,17 @@ impl Shell {
         }
     }
 
+    pub fn supports_osc9_4(&self) -> bool {
+        match &self.output {
+            ShellOut::Write(_) => false,
+            ShellOut::Stream {
+                progress_report,
+                stderr_tty,
+                ..
+            } => *progress_report && *stderr_tty,
+        }
+    }
+
     /// Gets the current color choice.
     ///
     /// If we are not using a color stream, this will always return `Never`, even if the color
@@ -426,6 +438,8 @@ enum ShellOut {
         hyperlinks: bool,
         stdout_unicode: bool,
         stderr_unicode: bool,
+        /// Whether the terminal supports progress notifications via OSC 9;4 sequences
+        progress_report: bool,
     },
 }
 
@@ -565,6 +579,15 @@ fn supports_unicode(stream: &dyn IsTerminal) -> bool {
     !stream.is_terminal() || supports_unicode::supports_unicode()
 }
 
+/// Detects if the terminal supports OSC 9;4 progress notifications.
+#[allow(clippy::disallowed_methods)] // ALLOWED: to read terminal app signature
+fn supports_progress_report() -> bool {
+    // Windows Terminal session.
+    std::env::var("WT_SESSION").is_ok()
+    // Compatibility with ConEmu's ANSI support.
+        || std::env::var("ConEmuANSI").ok() == Some("ON".into())
+}
+
 fn supports_hyperlinks() -> bool {
     #[allow(clippy::disallowed_methods)] // We are reading the state of the system, not config
     if std::env::var_os("TERM_PROGRAM").as_deref() == Some(std::ffi::OsStr::new("iTerm.app")) {

src/cargo/util/context/mod.rs

@@ -2747,8 +2747,10 @@ pub struct TermConfig {
 #[derive(Debug, Default, Deserialize)]
 #[serde(rename_all = "kebab-case")]
 pub struct ProgressConfig {
+    #[serde(default)]
     pub when: ProgressWhen,
     pub width: Option<usize>,
+    pub taskbar: Option<bool>,
 }
 
 #[derive(Debug, Default, Deserialize)]
@@ -2781,10 +2783,12 @@ where
                 "auto" => Ok(Some(ProgressConfig {
                     when: ProgressWhen::Auto,
                     width: None,
+                    taskbar: None,
                 })),
                 "never" => Ok(Some(ProgressConfig {
                     when: ProgressWhen::Never,
                     width: None,
+                    taskbar: None,
                 })),
                 "always" => Err(E::custom("\"always\" progress requires a `width` key")),
                 _ => Err(E::unknown_variant(s, &["auto", "never"])),
@@ -2806,6 +2810,7 @@ where
             if let ProgressConfig {
                 when: ProgressWhen::Always,
                 width: None,
+                ..
             } = pc
             {
                 return Err(serde::de::Error::custom(