[usdt] add global_slot, group_slot and test_group (#2716)

Useful for test attempt events.

Author: sunshowers

nextest-runner/src/config/elements/test_group.rs

@@ -23,6 +23,14 @@ impl TestGroup {
     /// The string `"@global"`, indicating the global test group.
     pub const GLOBAL_STR: &'static str = "@global";
 
+    /// Returns the custom group name if this is a custom group, or None if this is the global group.
+    pub fn custom_name(&self) -> Option<&str> {
+        match self {
+            TestGroup::Custom(group) => Some(group.as_str()),
+            TestGroup::Global => None,
+        }
+    }
+
     pub(crate) fn make_all_groups(
         custom_groups: impl IntoIterator<Item = CustomTestGroup>,
     ) -> impl Iterator<Item = Self> {

nextest-runner/src/runner/executor.rs

@@ -743,6 +743,13 @@ impl<'a> ExecutorContext<'a> {
             total_attempts: test.retry_data.total_attempts,
             stress_current: test.stress_index.map(|s| s.current),
             stress_total: test.stress_index.and_then(|s| s.total.map(|t| t.get())),
+            global_slot: test.cx.global_slot(),
+            group_slot: test.cx.group_slot(),
+            test_group: test
+                .settings
+                .test_group()
+                .custom_name()
+                .map(|s| s.to_owned()),
         });
 
         // If assigning the child to the job fails, ignore this. This can happen if the process has

nextest-runner/src/usdt.rs

@@ -302,6 +302,15 @@ pub struct UsdtTestAttemptStart {
 
     /// The total number of stress runs, if available.
     pub stress_total: Option<u32>,
+
+    /// The global slot number (0-indexed).
+    pub global_slot: u64,
+
+    /// The group slot number (0-indexed), if the test is in a custom test group.
+    pub group_slot: Option<u64>,
+
+    /// The test group name, if the test is in a custom test group.
+    pub test_group: Option<String>,
 }
 
 /// Data associated with the `test-attempt-done` probe.