chore: context stabilization tests & logging pieces

opentelemetry/Cargo.toml

@@ -43,6 +43,8 @@ internal-logs = ["tracing"]
 opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["spec_unstable_logs_enabled"]} # for documentation tests
 criterion = { workspace = true }
 rand = { workspace = true, features = ["os_rng", "thread_rng"] }
+tokio = { version = "1.0", features = ["full"] }
+futures = "0.3"
 
 [[bench]]
 name = "metrics"

opentelemetry/src/context.rs

@@ -460,6 +460,15 @@
             // The empty context is always at the bottom of the [`ContextStack`]
             // and cannot be popped, and the overflow position is invalid, so do
             // nothing.
+            otel_warn!(
+                name: "Context.PopInvalidPosition",
+                position = pos,
+                message = if pos == ContextStack::BASE_POS {
+                    "Attempted to pop the base context which is not allowed"
+                } else {
+                    "Attempted to pop the overflow position which is not allowed"
+                }
+            );
             return;
         }
         let len: u16 = self.stack.len() as u16;
@@ -479,6 +488,12 @@
             // This is an out of order pop.
             if pos >= len {
                 // This is an invalid id, ignore it.
+                otel_warn!(
+                    name: "Context.PopOutOfBounds",
+                    position = pos,
+                    stack_length = len,
+                    message = "Attempted to pop beyond the end of the context stack"
+                );
                 return;
             }
             // Clear out the entry at the given id.
@@ -505,6 +520,8 @@
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::time::Duration;
+    use tokio::time::sleep;
 
     #[derive(Debug, PartialEq)]
     struct ValueA(u64);
@@ -659,14 +676,186 @@
         }
     }
 
+    /// Tests that a new ContextStack is created with the correct initial capacity.
+    #[test]
+    fn test_initial_capacity() {
+        let stack = ContextStack::default();
+        assert_eq!(stack.stack.capacity(), ContextStack::INITIAL_CAPACITY);
+    }
+
+    /// Tests that map_current_cx correctly accesses the current context.
     #[test]
-    fn context_stack_pop_id() {
-        // This is to get full line coverage of the `pop_id` function.
-        // In real life the `Drop`` implementation of `ContextGuard` ensures that
-        // the ids are valid and inside the bounds.
+    fn test_map_current_cx() {
         let mut stack = ContextStack::default();
+        let test_value = ValueA(42);
+        stack.current_cx = Context::new().with_value(test_value);
+
+        let result = stack.map_current_cx(|cx| {
+            assert_eq!(cx.get::<ValueA>(), Some(&ValueA(42)));
+            true
+        });
+        assert!(result);
+    }
+
+    /// Tests popping contexts in non-sequential order.
+    #[test]
+    fn test_pop_id_out_of_order() {
+        let mut stack = ContextStack::default();
+
+        // Push three contexts
+        let cx1 = Context::new().with_value(ValueA(1));
+        let cx2 = Context::new().with_value(ValueA(2));
+        let cx3 = Context::new().with_value(ValueA(3));
+
+        let id1 = stack.push(cx1);
+        let id2 = stack.push(cx2);
+        let id3 = stack.push(cx3);
+
+        // Pop middle context first - should not affect current context
+        stack.pop_id(id2);
+        assert_eq!(stack.current_cx.get::<ValueA>(), Some(&ValueA(3)));
+        assert_eq!(stack.stack.len(), 3); // Length unchanged for middle pops
+
+        // Pop last context - should restore previous valid context
+        stack.pop_id(id3);
+        assert_eq!(stack.current_cx.get::<ValueA>(), Some(&ValueA(1)));
+        assert_eq!(stack.stack.len(), 1);
+
+        // Pop first context - should restore to empty state
+        stack.pop_id(id1);
+        assert_eq!(stack.current_cx.get::<ValueA>(), None);
+        assert_eq!(stack.stack.len(), 0);
+    }
+
+    /// Tests edge cases in context stack operations. IRL these should log
+    /// warnings, and definitely not panic.
+    #[test]
+    fn test_pop_id_edge_cases() {
+        let mut stack = ContextStack::default();
+
+        // Test popping BASE_POS - should be no-op
         stack.pop_id(ContextStack::BASE_POS);
+        assert_eq!(stack.stack.len(), 0);
+
+        // Test popping MAX_POS - should be no-op
         stack.pop_id(ContextStack::MAX_POS);
-        stack.pop_id(4711);
+        assert_eq!(stack.stack.len(), 0);
+
+        // Test popping invalid position - should be no-op
+        stack.pop_id(1000);
+        assert_eq!(stack.stack.len(), 0);
+
+        // Test popping from empty stack - should be safe
+        stack.pop_id(1);
+        assert_eq!(stack.stack.len(), 0);
+    }
+
+    /// Tests stack behavior when reaching maximum capacity.
+    /// Once we push beyond this point, we should end up with a context
+    /// that points _somewhere_, but mutating it should not affect the current
+    /// active context.
+    #[test]
+    fn test_push_overflow() {
+        let mut stack = ContextStack::default();
+        let max_pos = ContextStack::MAX_POS as usize;
+
+        // Fill stack up to max position
+        for i in 0..max_pos {
+            let cx = Context::new().with_value(ValueA(i as u64));
+            let id = stack.push(cx);
+            assert_eq!(id, (i + 1) as u16);
+        }
+
+        // Try to push beyond capacity
+        let cx = Context::new().with_value(ValueA(max_pos as u64));
+        let id = stack.push(cx);
+        assert_eq!(id, ContextStack::MAX_POS);
+
+        // Verify current context remains unchanged after overflow
+        assert_eq!(
+            stack.current_cx.get::<ValueA>(),
+            Some(&ValueA((max_pos - 2) as u64))
+        );
+    }
+
+    /// Tests that:
+    /// 1. Parent context values are properly propagated to async operations
+    /// 2. Values added during async operations do not affect parent context
+    #[tokio::test]
+    async fn test_async_context_propagation() {
+        // Set up initial context with ValueA
+        let parent_cx = Context::new().with_value(ValueA(42));
+
+        // Create and run async operation with the parent context
+        async {
+            // Verify we can see the parent context's value
+            assert_eq!(
+                Context::current().get::<ValueA>(),
+                Some(&ValueA(42)),
+                "Parent context value should be available in async operation"
+            );
+
+            // Create new context with both values
+            let cx_with_both = Context::current().with_value(ValueB(24));
+
+            // Run nested async operation with both values
+            async {
+                // Verify both values are available
+                assert_eq!(
+                    Context::current().get::<ValueA>(),
+                    Some(&ValueA(42)),
+                    "Parent value should still be available after adding new value"
+                );
+                assert_eq!(
+                    Context::current().get::<ValueB>(),
+                    Some(&ValueB(24)),
+                    "New value should be available in async operation"
+                );
+
+                // Do some async work to simulate real-world scenario
+                sleep(Duration::from_millis(10)).await;
+
+                // Values should still be available after async work
+                assert_eq!(
+                    Context::current().get::<ValueA>(),
+                    Some(&ValueA(42)),
+                    "Parent value should persist across await points"
+                );
+                assert_eq!(
+                    Context::current().get::<ValueB>(),
+                    Some(&ValueB(24)),
+                    "New value should persist across await points"
+                );
+            }
+            .with_context(cx_with_both)
+            .await;
+        }
+        .with_context(parent_cx.clone()) // Propagate the parent context to the async operation
+        .await;
+
+        // After async operation completes:
+        // 1. Parent context should be unchanged
+        assert_eq!(
+            parent_cx.get::<ValueA>(),
+            Some(&ValueA(42)),
+            "Parent context should be unchanged"
+        );
+        assert_eq!(
+            parent_cx.get::<ValueB>(),
+            None,
+            "Parent context should not see values added in async operation"
+        );
+
+        // 2. Current context should be back to default
+        assert_eq!(
+            Context::current().get::<ValueA>(),
+            None,
+            "Current context should be back to default"
+        );
+        assert_eq!(
+            Context::current().get::<ValueB>(),
+            None,
+            "Current context should not have async operation's values"
+        );
     }
 }