fix: gate VecMap PartialEq behind test-utils, fix FFI key dedup and deletion

VecMap PartialEq is now HashMap-based (order-independent) and only
available in test/test-utils builds. FFI delete functions use
remove_slow for correct has/del semantics. get_keys deduplicates
output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: yannham

datadog-sidecar-ffi/Cargo.toml

@@ -35,6 +35,7 @@ libdd-crashtracker-ffi = { path = "../libdd-crashtracker-ffi", features = ["coll
 
 [dev-dependencies]
 http = "1.1"
+libdd-trace-utils = { path = "../libdd-trace-utils", features = ["test-utils"] }
 tempfile = { version = "3.3" }
 
 [lints.rust]

datadog-sidecar-ffi/src/span.rs

@@ -7,7 +7,6 @@ use libdd_trace_utils::span::v04::{
     AttributeAnyValueBytes, AttributeArrayValueBytes, SpanBytes, SpanEventBytes, SpanLinkBytes,
     VecMap,
 };
-use libdd_trace_utils::span::vec_map::Tombstone;
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::ffi::{c_char, CString};
@@ -67,12 +66,6 @@ fn remove_vec_map_slow<V>(map: &mut VecMap<BytesString, V>, key: CharSlice) {
     map.remove_slow(&bytes_str_key);
 }
 
-#[inline]
-fn remove_vec_map<V: Tombstone>(map: &mut VecMap<BytesString, V>, key: CharSlice) {
-    let bytes_str_key = convert_char_slice_to_bytes_string(key);
-    map.remove_unset(&bytes_str_key);
-}
-
 #[inline]
 fn exists_vec_map<V>(map: &VecMap<BytesString, V>, key: CharSlice) -> bool {
     let bytes_str_key = convert_char_slice_to_bytes_string(key);
@@ -87,6 +80,7 @@ fn get_vec_map_keys<'a, V>(
 ) -> *mut CharSlice<'a> {
     let mut keys: Vec<&str> = map.iter().map(|(k, _)| k.as_str()).collect();
     keys.sort_unstable();
+    keys.dedup();
 
     let slices: Box<[CharSlice]> = keys
         .iter()
@@ -350,7 +344,7 @@ pub extern "C" fn ddog_add_span_meta(span: &mut SpanBytes, key: CharSlice, value
 
 #[no_mangle]
 pub extern "C" fn ddog_del_span_meta(span: &mut SpanBytes, key: CharSlice) {
-    remove_vec_map(&mut span.meta, key);
+    remove_vec_map_slow(&mut span.meta, key);
 }
 
 #[no_mangle]

datadog-sidecar-ffi/tests/span.rs

@@ -186,7 +186,7 @@ fn test_span_debug_log_output() {
     ddog_set_span_name(span, CharSlice::from("debug-span"));
     let debug_output = ddog_span_debug_log(span);
 
-    let expected_output = CharSlice::from("Span { service: , name: debug-span, resource: , type: , trace_id: 0, span_id: 0, parent_id: 0, start: 0, duration: 0, error: 0, meta: [], metrics: [], meta_struct: [], span_links: [], span_events: [] }");
+    let expected_output = CharSlice::from("Span { service: , name: debug-span, resource: , type: , trace_id: 0, span_id: 0, parent_id: 0, start: 0, duration: 0, error: 0, meta: VecMap([]), metrics: VecMap([]), meta_struct: VecMap([]), span_links: [], span_events: [] }");
 
     assert_eq!(debug_output, expected_output);
 

libdd-trace-utils/src/span/v04/mod.rs

@@ -76,7 +76,8 @@ fn is_empty_str<T: Borrow<str>>(value: &T) -> bool {
 ///     let _ = span.meta.get("foo");
 /// }
 /// ```
-#[derive(Debug, Default, PartialEq, Serialize)]
+#[derive(Debug, Default, Serialize)]
+#[cfg_attr(any(test, feature = "test-utils"), derive(PartialEq))]
 pub struct Span<T: TraceData> {
     pub service: T::Text,
     pub name: T::Text,

libdd-trace-utils/src/span/vec_map.rs

@@ -31,9 +31,21 @@ use std::hash::Hash;
 /// Explicit deduplication is currently being done automatically and on-the-fly during
 /// serialization. If needed, in the future, we might trigger deduplication on other events, for
 /// example at insertion if the size is bigger than a threshold.
-#[derive(Clone, Debug, PartialEq, Default)]
+#[derive(Clone, Debug, Default)]
 pub struct VecMap<K, V>(Vec<(K, V)>);
 
+#[cfg(any(test, feature = "test-utils"))]
+impl<K: Eq + Hash, V: PartialEq> PartialEq for VecMap<K, V> {
+    fn eq(&self, other: &Self) -> bool {
+        let lhs: HashMap<&K, &V> = self.0.iter().map(|(k, v)| (k, v)).collect();
+        let rhs: HashMap<&K, &V> = other.0.iter().map(|(k, v)| (k, v)).collect();
+        lhs == rhs
+    }
+}
+
+#[cfg(any(test, feature = "test-utils"))]
+impl<K: Eq + Hash, V: PartialEq> Eq for VecMap<K, V> {}
+
 /// Values that can be replaced by a special tombstone value that makes them to be ignored later in
 /// the pipeline. This makes their removal from a [VecMap] a bit more efficient (still a linear
 /// scan, but no shifting involved). Technically equivalent to [Default], but of course having a