Add section timing data to JSON --timings output

Author: Kobzol

src/cargo/core/compiler/mod.rs

@@ -105,6 +105,7 @@ use cargo_util_schemas::manifest::TomlDebugInfo;
 use cargo_util_schemas::manifest::TomlTrimPaths;
 use cargo_util_schemas::manifest::TomlTrimPathsValue;
 use rustfix::diagnostics::Applicability;
+pub(crate) use timings::CompilationSection;
 
 const RUSTDOC_CRATE_VERSION_FLAG: &str = "--crate-version";
 

src/cargo/core/compiler/timings.rs

@@ -12,6 +12,7 @@ use crate::util::style;
 use crate::util::{CargoResult, GlobalContext};
 use anyhow::Context as _;
 use cargo_util::paths;
+use indexmap::IndexMap;
 use std::collections::HashMap;
 use std::io::{BufWriter, Write};
 use std::thread::available_parallelism;
@@ -64,8 +65,9 @@ pub struct Timings<'gctx> {
     cpu_usage: Vec<(f64, f64)>,
 }
 
-/// Section of compilation.
-struct TimingSection {
+/// Section of compilation (e.g. frontend, backend, linking).
+#[derive(Copy, Clone, serde::Serialize)]
+pub struct CompilationSection {
     /// Start of the section, as an offset in seconds from `UnitTime::start`.
     start: f64,
     /// End of the section, as an offset in seconds from `UnitTime::start`.
@@ -89,7 +91,10 @@ struct UnitTime {
     /// Same as `unlocked_units`, but unlocked by rmeta.
     unlocked_rmeta_units: Vec<Unit>,
     /// Individual compilation section durations, gathered from `--json=timings`.
-    sections: HashMap<String, TimingSection>,
+    ///
+    /// IndexMap is used to keep original insertion order, we want to be able to tell which
+    /// sections were started in which order.
+    sections: IndexMap<String, CompilationSection>,
 }
 
 /// Periodic concurrency tracking information.
@@ -238,6 +243,7 @@ impl<'gctx> Timings<'gctx> {
                 mode: unit_time.unit.mode,
                 duration: unit_time.duration,
                 rmeta_time: unit_time.rmeta_time,
+                sections: unit_time.sections.clone().into_iter().collect(),
             }
             .to_json_string();
             crate::drop_println!(self.gctx, "{}", msg);
@@ -616,20 +622,20 @@ impl UnitTime {
             .sections
             .insert(
                 name.to_string(),
-                TimingSection {
+                CompilationSection {
                     start: now - self.start,
                     end: None,
                 },
             )
             .is_some()
         {
-            warn!("Compilation section {name} started more than once");
+            warn!("compilation section {name} started more than once");
         }
     }
 
     fn end_section(&mut self, name: &str, now: f64) {
         let Some(section) = self.sections.get_mut(name) else {
-            warn!("Compilation section {name} ended, but it has no start recorded");
+            warn!("compilation section {name} ended, but it has no start recorded");
             return;
         };
         section.end = Some(now - self.start);

src/cargo/util/machine_message.rs

@@ -6,7 +6,7 @@ use serde::ser;
 use serde_json::{json, value::RawValue};
 
 use crate::core::Target;
-use crate::core::compiler::CompileMode;
+use crate::core::compiler::{CompilationSection, CompileMode};
 
 pub trait Message: ser::Serialize {
     fn reason(&self) -> &str;
@@ -95,6 +95,8 @@ pub struct TimingInfo<'a> {
     pub duration: f64,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub rmeta_time: Option<f64>,
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    pub sections: Vec<(String, CompilationSection)>,
 }
 
 impl<'a> Message for TimingInfo<'a> {