Fix .NET clone dropping ExpAssignments + add clone regression coverage

ellismg · Copilot · ellismg · commit e3cbdaa83112 · 2026-06-23T10:37:01.000-07:00
The SessionConfigBase copy constructor (used by SessionConfig.Clone() and
ResumeSessionConfig.Clone()) did not copy the newly added ExpAssignments
property, so cloning a config silently dropped it and it would not be
forwarded on create/resume. Copy it alongside the other base properties.

Cross-language audit of every config copy/clone path:
- .NET: had the gap (fixed here).
- Java: SessionConfig/ResumeSessionConfig clone() already copy expAssignments (safe).
- Rust: SessionConfig/ResumeSessionConfig derive Clone, no manual impl (safe).
- Node: createSession/resumeSession normalize via { ...defaults, ...config }
  spread, which preserves all own properties (safe).
- Go: create/resume requests assign req.ExpAssignments = config.ExpAssignments
  directly from the config pointer (safe).
- Python: exp_assignments is an explicit kwarg mapped straight into the
  payload, no intermediate dict copy (safe).

Add clone regression tests for .NET, Java, and Rust (the three with explicit
Clone()/clone() methods) that set expAssignments, clone, and assert it
survives and is forwarded on the resulting create/resume request. The .NET
tests fail against the pre-fix copy constructor. Node's existing forward test
already exercises the spread-normalization copy path.

Switch the two new Java expAssignments tests off the deprecated
buildCreateRequest(SessionConfig) overload to the current
buildCreateRequest(SessionConfig, String) form to avoid new CodeQL debt.

Co-authored-by: Copilot &lt;223556219+Copilot@users.noreply.github.com&gt;
diff --git a/dotnet/src/Types.cs b/dotnet/src/Types.cs
@@ -2667,6 +2667,7 @@ protected SessionConfigBase(SessionConfigBase? other)
         CreateSessionFsProvider = other.CreateSessionFsProvider;
         GitHubToken = other.GitHubToken;
         RemoteSession = other.RemoteSession;
+        ExpAssignments = other.ExpAssignments;
 #pragma warning disable GHCP001
         Canvases = other.Canvases is not null ? [.. other.Canvases] : null;
         RequestCanvasRenderer = other.RequestCanvasRenderer;
diff --git a/dotnet/test/Unit/SerializationTests.cs b/dotnet/test/Unit/SerializationTests.cs
@@ -496,6 +496,43 @@ public void SessionRequests_OmitExpAssignments_WhenUnset()
         Assert.False(resumeDocument.RootElement.TryGetProperty("expAssignments", out _));
     }
 
+    [Fact]
+    public void SessionConfigClone_PreservesExpAssignments()
+    {
+        using var assignments = JsonDocument.Parse("""{"Configs":[{"Id":"exp-create"}]}""");
+
+        var config = new SessionConfig
+        {
+            SessionId = "session-id",
+            ExpAssignments = assignments.RootElement.Clone(),
+        };
+
+        var clone = config.Clone();
+
+        Assert.True(clone.ExpAssignments.HasValue);
+        Assert.Equal(
+            "exp-create",
+            clone.ExpAssignments!.Value.GetProperty("Configs")[0].GetProperty("Id").GetString());
+    }
+
+    [Fact]
+    public void ResumeSessionConfigClone_PreservesExpAssignments()
+    {
+        using var assignments = JsonDocument.Parse("""{"Configs":[{"Id":"exp-resume"}]}""");
+
+        var config = new ResumeSessionConfig
+        {
+            ExpAssignments = assignments.RootElement.Clone(),
+        };
+
+        var clone = config.Clone();
+
+        Assert.True(clone.ExpAssignments.HasValue);
+        Assert.Equal(
+            "exp-resume",
+            clone.ExpAssignments!.Value.GetProperty("Configs")[0].GetProperty("Id").GetString());
+    }
+
     [Fact]
     public void CreateSessionRequest_CanSerializeEnableSessionTelemetry_WithSdkOptions()
     {
diff --git a/java/src/test/java/com/github/copilot/SessionRequestBuilderTest.java b/java/src/test/java/com/github/copilot/SessionRequestBuilderTest.java
@@ -876,7 +876,7 @@ void testBuildRequestsPropagateAndSerializeExpAssignments() throws Exception {
         JsonNode resumeAssignments = mapper.readTree("{\"Configs\":[{\"Id\":\"exp-resume\"}]}");
 
         var createConfig = new SessionConfig().setExpAssignments(createAssignments);
-        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(createConfig);
+        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(createConfig, "session-1");
         assertEquals(createAssignments, createRequest.getExpAssignments());
         var createJson = mapper.writeValueAsString(createRequest);
         assertTrue(createJson.contains("\"expAssignments\""));
@@ -894,7 +894,7 @@ void testBuildRequestsPropagateAndSerializeExpAssignments() throws Exception {
     void testBuildRequestsOmitExpAssignmentsWhenUnset() throws Exception {
         var mapper = JsonRpcClient.getObjectMapper();
 
-        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(new SessionConfig());
+        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(new SessionConfig(), "session-1");
         assertNull(createRequest.getExpAssignments());
         var createJson = mapper.writeValueAsString(createRequest);
         assertFalse(createJson.contains("\"expAssignments\""), "expAssignments should be omitted when null");
@@ -905,4 +905,25 @@ void testBuildRequestsOmitExpAssignmentsWhenUnset() throws Exception {
         var resumeJson = mapper.writeValueAsString(resumeRequest);
         assertFalse(resumeJson.contains("\"expAssignments\""), "expAssignments should be omitted when null");
     }
+
+    @Test
+    void testClonePreservesAndForwardsExpAssignments() throws Exception {
+        var mapper = JsonRpcClient.getObjectMapper();
+        JsonNode createAssignments = mapper.readTree("{\"Configs\":[{\"Id\":\"exp-create\"}]}");
+        JsonNode resumeAssignments = mapper.readTree("{\"Configs\":[{\"Id\":\"exp-resume\"}]}");
+
+        var createConfig = new SessionConfig().setExpAssignments(createAssignments);
+        SessionConfig createClone = createConfig.clone();
+        assertEquals(createAssignments, createClone.getExpAssignments());
+        CreateSessionRequest createRequest = SessionRequestBuilder.buildCreateRequest(createClone, "session-1");
+        assertEquals(createAssignments, createRequest.getExpAssignments());
+        assertTrue(mapper.writeValueAsString(createRequest).contains("\"Id\":\"exp-create\""));
+
+        var resumeConfig = new ResumeSessionConfig().setExpAssignments(resumeAssignments);
+        ResumeSessionConfig resumeClone = resumeConfig.clone();
+        assertEquals(resumeAssignments, resumeClone.getExpAssignments());
+        ResumeSessionRequest resumeRequest = SessionRequestBuilder.buildResumeRequest("session-1", resumeClone);
+        assertEquals(resumeAssignments, resumeRequest.getExpAssignments());
+        assertTrue(mapper.writeValueAsString(resumeRequest).contains("\"Id\":\"exp-resume\""));
+    }
 }
diff --git a/rust/src/types.rs b/rust/src/types.rs
@@ -5030,6 +5030,41 @@ mod tests {
         assert!(empty_json.get("expAssignments").is_none());
     }
 
+    #[test]
+    fn session_config_clone_preserves_exp_assignments() {
+        let assignments = serde_json::json!({
+            "Parameters": { "copilot_exp_flag": "treatment" },
+            "AssignmentContext": "ctx-clone",
+        });
+        let config = SessionConfig::default().with_exp_assignments(assignments.clone());
+        let cloned = config.clone();
+
+        assert_eq!(cloned.exp_assignments.as_ref(), Some(&assignments));
+
+        let (wire, _runtime) = cloned
+            .into_wire(Some(SessionId::from("exp-clone")))
+            .expect("no duplicate handlers");
+        let json = serde_json::to_value(&wire).unwrap();
+        assert_eq!(json["expAssignments"], assignments);
+    }
+
+    #[test]
+    fn resume_session_config_clone_preserves_exp_assignments() {
+        let assignments = serde_json::json!({
+            "Parameters": { "copilot_exp_flag": "treatment" },
+            "AssignmentContext": "ctx-clone-resume",
+        });
+        let config = ResumeSessionConfig::new(SessionId::from("resume-exp-clone"))
+            .with_exp_assignments(assignments.clone());
+        let cloned = config.clone();
+
+        assert_eq!(cloned.exp_assignments.as_ref(), Some(&assignments));
+
+        let (wire, _runtime) = cloned.into_wire().expect("no duplicate handlers");
+        let json = serde_json::to_value(&wire).unwrap();
+        assert_eq!(json["expAssignments"], assignments);
+    }
+
     #[test]
     #[allow(clippy::field_reassign_with_default)]
     fn session_config_into_wire_serializes_bucket_b_fields() {
