Diagnostic summary

src/bin/cargo/cli.rs

@@ -341,6 +341,14 @@ fn config_configure(
     if let Some(values) = args.get_many::<String>("config") {
         config_args.extend(values.cloned());
     }
+    let summary_override = if subcommand_args.flag("summary") {
+        Some(true)
+    } else if subcommand_args.flag("no-summary") {
+        Some(false)
+    } else {
+        None
+    };
+
     config.configure(
         verbose,
         quiet,
@@ -349,6 +357,7 @@ fn config_configure(
         locked,
         offline,
         arg_target_dir,
+        summary_override,
         &unstable_flags,
         &config_args,
     )?;

src/bin/cargo/commands/build.rs

@@ -45,6 +45,8 @@ pub fn cli() -> Command {
         .arg_unit_graph()
         .arg_future_incompat_report()
         .arg_timings()
+        .arg_show_summary()
+        .arg_hide_summary()
         .after_help("Run `cargo help build` for more detailed information.\n")
 }
 

src/bin/cargo/commands/check.rs

@@ -37,6 +37,8 @@ pub fn cli() -> Command {
         .arg_unit_graph()
         .arg_future_incompat_report()
         .arg_timings()
+        .arg_show_summary()
+        .arg_hide_summary()
         .after_help("Run `cargo help check` for more detailed information.\n")
 }
 

src/bin/cargo/commands/run.rs

@@ -32,6 +32,8 @@ pub fn cli() -> Command {
         .arg_unit_graph()
         .arg_ignore_rust_version()
         .arg_timings()
+        .arg_show_summary()
+        .arg_hide_summary()
         .after_help("Run `cargo help run` for more detailed information.\n")
 }
 

src/cargo/core/compiler/job_queue.rs

@@ -132,6 +132,7 @@ struct DrainState<'cfg> {
     diag_dedupe: DiagDedupe<'cfg>,
     /// Count of warnings, used to print a summary after the job succeeds
     warning_count: HashMap<JobId, WarningCount>,
+    diagnostic_codes: HashMap<JobId, HashMap<String, usize>>,
     active: HashMap<JobId, Unit>,
     compiled: HashSet<PackageId>,
     documented: HashSet<PackageId>,
@@ -202,6 +203,9 @@ impl WarningCount {
     }
 }
 
+// If the total number of diagnostics is at least this many, then output a summary.
+const DIAGNOSTIC_SUMMARY_THRESHOLD: usize = 10;
+
 /// Used to keep track of how many fixable warnings there are
 /// and if fixable warnings are allowed
 #[derive(Default)]
@@ -356,6 +360,7 @@ enum Message {
         level: String,
         diag: String,
         fixable: bool,
+        code: Option<String>,
     },
     // This handles duplicate output that is suppressed, for showing
     // only a count of duplicate messages instead
@@ -420,7 +425,13 @@ impl<'a, 'cfg> JobState<'a, 'cfg> {
     }
 
     /// See [`Message::Diagnostic`] and [`Message::WarningCount`].
-    pub fn emit_diag(&self, level: String, diag: String, fixable: bool) -> CargoResult<()> {
+    pub fn emit_diag(
+        &self,
+        level: String,
+        diag: String,
+        fixable: bool,
+        code: Option<String>,
+    ) -> CargoResult<()> {
         if let Some(dedupe) = self.output {
             let emitted = dedupe.emit_diag(&diag)?;
             if level == "warning" {
@@ -436,6 +447,7 @@ impl<'a, 'cfg> JobState<'a, 'cfg> {
                 level,
                 diag,
                 fixable,
+                code,
             });
         }
         Ok(())
@@ -586,6 +598,7 @@ impl<'cfg> JobQueue<'cfg> {
             messages: Arc::new(Queue::new(100)),
             diag_dedupe: DiagDedupe::new(cx.bcx.config),
             warning_count: HashMap::new(),
+            diagnostic_codes: HashMap::new(),
             active: HashMap::new(),
             compiled: HashSet::new(),
             documented: HashSet::new(),
@@ -755,7 +768,11 @@ impl<'cfg> DrainState<'cfg> {
                 level,
                 diag,
                 fixable,
+                code,
             } => {
+                if let Some(code) = code {
+                    self.bump_diagnostic_count(id, code);
+                }
                 let emitted = self.diag_dedupe.emit_diag(&diag)?;
                 if level == "warning" {
                     self.bump_warning_count(id, emitted, fixable);
@@ -1247,6 +1264,12 @@ impl<'cfg> DrainState<'cfg> {
         }
     }
 
+    fn bump_diagnostic_count(&mut self, id: JobId, code: String) {
+        let code_counts = self.diagnostic_codes.entry(id).or_default();
+        let total = code_counts.entry(code).or_default();
+        *total += 1;
+    }
+
     /// Displays a final report of the warnings emitted by a particular job.
     fn report_warning_count(
         &mut self,
@@ -1320,6 +1343,30 @@ impl<'cfg> DrainState<'cfg> {
                 }
             }
         }
+
+        let mut diag_stats: Vec<(String, usize)> = self
+            .diagnostic_codes
+            .remove(&id)
+            .unwrap_or_default()
+            .into_iter()
+            .collect();
+        let total_diag_count: usize = diag_stats.iter().map(|(_, count)| count).sum();
+
+        let print_summary = config
+            .summary_override
+            .unwrap_or(total_diag_count >= DIAGNOSTIC_SUMMARY_THRESHOLD);
+        if print_summary {
+            // we sort the each diagnostic count by count and name. We will primarily sort descending by count, and for
+            // entries with the same count we shall sort by alphabetic order by the lint name.
+            diag_stats
+                .sort_by(|(name1, count1), (name2, count2)| (count2, name1).cmp(&(count1, name2)));
+            message.push_str("\n\n");
+            message.push_str("Summary of diagnostics:\n");
+            for (name, count) in diag_stats {
+                message.push_str(format!("{name}: {count}\n").as_str());
+            }
+        }
+
         // Errors are ignored here because it is tricky to handle them
         // correctly, and they aren't important.
         drop(config.shell().warn(message));

src/cargo/core/compiler/mod.rs

@@ -1502,12 +1502,17 @@ fn on_stderr_line_inner(
             render_diagnostics: true,
             ..
         } => {
+            #[derive(serde::Deserialize)]
+            struct DiagnosticCode {
+                code: String,
+            }
             #[derive(serde::Deserialize)]
             struct CompilerMessage {
                 rendered: String,
                 message: String,
                 level: String,
                 children: Vec<PartialDiagnostic>,
+                code: Option<DiagnosticCode>,
             }
 
             // A partial rustfix::diagnostics::Diagnostic. We deserialize only a
@@ -1563,7 +1568,12 @@ fn on_stderr_line_inner(
                         })
                         .any(|b| b);
                     count_diagnostic(&msg.level, options);
-                    state.emit_diag(msg.level, rendered, machine_applicable)?;
+                    state.emit_diag(
+                        msg.level,
+                        rendered,
+                        machine_applicable,
+                        msg.code.map(|code| code.code),
+                    )?;
                 }
                 return Ok(true);
             }

src/cargo/util/command_prelude.rs

@@ -252,6 +252,14 @@ pub trait CommandExt: Sized {
             .require_equals(true),
         )
     }
+
+    fn arg_show_summary(self) -> Self {
+        self._arg(flag("summary", "Show diagnostic summary"))
+    }
+
+    fn arg_hide_summary(self) -> Self {
+        self._arg(flag("no-summary", "Suppress diagnostic summary"))
+    }
 }
 
 impl CommandExt for Command {

src/cargo/util/config/mod.rs

@@ -245,6 +245,9 @@ pub struct Config {
     pub nightly_features_allowed: bool,
     /// WorkspaceRootConfigs that have been found
     pub ws_roots: RefCell<HashMap<PathBuf, WorkspaceRootConfig>>,
+    /// By default, a summary is shown if `cargo clippy` gives many warnings.
+    /// This field overrides default behavior if the option is a Some variant.
+    pub summary_override: Option<bool>,
 }
 
 impl Config {
@@ -331,6 +334,7 @@ impl Config {
             env_config: LazyCell::new(),
             nightly_features_allowed: matches!(&*features::channel(), "nightly" | "dev"),
             ws_roots: RefCell::new(HashMap::new()),
+            summary_override: None,
         }
     }
 
@@ -957,6 +961,7 @@ impl Config {
         locked: bool,
         offline: bool,
         target_dir: &Option<PathBuf>,
+        summary_override: Option<bool>,
         unstable_flags: &[String],
         cli_config: &[String],
     ) -> CargoResult<()> {
@@ -1024,6 +1029,7 @@ impl Config {
                 .and_then(|n| n.offline)
                 .unwrap_or(false);
         self.target_dir = cli_target_dir;
+        self.summary_override = summary_override;
 
         self.load_unstable_flags_from_config()?;
 

tests/testsuite/config.rs

@@ -88,6 +88,7 @@ impl ConfigBuilder {
             false,
             false,
             &None,
+            None,
             &self.unstable,
             &self.config_args,
         )?;