fix: qualify source-less dotnet stack frames

src/PostHog/ErrorTracking/ExceptionPropertiesBuilder.cs

@@ -103,6 +103,7 @@
 
             var method = frame.GetMethod();
             var fileName = frame.GetFileName();
+            var moduleName = method?.DeclaringType?.FullName ?? "";
             var lineNumber = frame.GetFileLineNumber();
             var columnNumber = frame.GetFileColumnNumber();
 
@@ -112,8 +113,8 @@
                 ["lang"] = "dotnet",
                 ["filename"] = Path.GetFileName(fileName) ?? "",
                 ["abs_path"] = fileName ?? "",
-                ["function"] = method?.Name ?? "",
-                ["module"] = method?.DeclaringType?.FullName ?? "",
+                ["function"] = BuildFunctionName(method?.Name, moduleName, fileName),
+                ["module"] = moduleName,
                 ["lineno"] = lineNumber,
                 ["colno"] = columnNumber
             };
@@ -137,6 +138,21 @@
         return stackFrames;
     }
 
+    private static string BuildFunctionName(string? methodName, string moduleName, string? fileName)
+    {
+        if (string.IsNullOrEmpty(methodName))
+        {
+            return "";
+        }
+
+        if (!string.IsNullOrEmpty(fileName) || string.IsNullOrEmpty(moduleName))
+        {
+            return methodName;
+        }
+
+        return $"{moduleName}.{methodName}";
+    }
+
     private static SourceCodeContext BuildSourceCodeContext(
         string absolutePath,
         int lineNumber,

tests/UnitTests/PostHogClientTests.cs

@@ -1278,6 +1278,71 @@ public static void Boom()
 
     // This test is pretty expensive because it dynamically compiles and loads an assembly.
     // Consider alternatives.
+    [Fact]
+    public async Task CaptureExceptionWithoutSourceInfoQualifiesFunctionName()
+    {
+        var (_, requestHandler, client) = CreateClient();
+
+        var code =
+            """
+            using System;
+            namespace SourceLessFrames;
+
+            public static class Thrower
+            {
+                public static void Boom()
+                {
+                    throw new InvalidOperationException("No source info");
+                }
+            }
+            """;
+
+        var tree = CSharpSyntaxTree.ParseText(SourceText.From(code, Encoding.UTF8));
+        var trustedPlatformAssemblies = ((string)AppContext.GetData("TRUSTED_PLATFORM_ASSEMBLIES")!).Split(Path.PathSeparator);
+
+        var refs = trustedPlatformAssemblies
+            .Where(p => p.EndsWith(".dll", StringComparison.OrdinalIgnoreCase))
+            .GroupBy(Path.GetFileName, StringComparer.OrdinalIgnoreCase)
+            .Select(g => MetadataReference.CreateFromFile(g.First()));
+
+        var comp = CSharpCompilation.Create(
+            $"ThrowerAsm{Guid.NewGuid():N}",
+            [tree],
+            refs,
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary, optimizationLevel: OptimizationLevel.Release));
+
+        using var pe = new MemoryStream();
+        var emit = comp.Emit(pe);
+        Assert.True(emit.Success, string.Join(Environment.NewLine, emit.Diagnostics));
+
+        pe.Position = 0;
+
+        var assemblyLoadContext = new AssemblyLoadContext($"ThrowerCtx{Guid.NewGuid():N}", isCollectible: true);
+        var assembly = assemblyLoadContext.LoadFromStream(pe);
+        var boom = assembly.GetType("SourceLessFrames.Thrower")!.GetMethod("Boom", BindingFlags.Public | BindingFlags.Static)!;
+
+        try
+        {
+            boom.Invoke(null, null);
+        }
+        catch (TargetInvocationException tie) when (tie.InnerException is InvalidOperationException ex)
+        {
+            client.CaptureException(ex, "some-distinct-id");
+            await client.FlushAsync();
+
+            var (_, batchItem, props) = ParseSingleEvent(requestHandler.GetReceivedRequestBody(indented: true));
+            var invalidOperationException = GetExceptionOfType(props, "System.InvalidOperationException");
+            var frames = GetStackFrames(invalidOperationException);
+
+            Assert.Equal("$exception", batchItem.GetProperty("event").GetString());
+            Assert.Equal("", frames[0].GetProperty("filename").GetString());
+            Assert.Equal("", frames[0].GetProperty("abs_path").GetString());
+            Assert.Equal("SourceLessFrames.Thrower", frames[0].GetProperty("module").GetString());
+            Assert.Equal("SourceLessFrames.Thrower.Boom", frames[0].GetProperty("function").GetString());
+            Assert.Equal(0, frames[0].GetProperty("lineno").GetInt32());
+        }
+    }
+
     [Fact]
     public async Task CaptureExceptionWithInvalidFilePathInStackFrame()
     {
@@ -1338,10 +1403,13 @@ public static void Boom()
 
             var divideByZeroException = GetExceptionOfType(props, "System.DivideByZeroException");
             var frames = GetStackFrames(divideByZeroException);
+            var sourceFrame = frames.FirstOrDefault(f =>
+                f.TryGetProperty("filename", out var filename) &&
+                string.Equals(filename.GetString(), fakePath, StringComparison.Ordinal));
 
             Assert.Equal("$exception", batchItem.GetProperty("event").GetString());
-            Assert.Equal(fakePath, frames[0].GetProperty("filename").GetString());
-            AssertContextEmpty(frames[0]);
+            Assert.NotEqual(JsonValueKind.Undefined, sourceFrame.ValueKind);
+            AssertContextEmpty(sourceFrame);
         }
     }
 
@@ -2009,4 +2077,4 @@ await Assert.ThrowsAsync<OperationCanceledException>(() =>
         Assert.DoesNotContain(errorLogs, log =>
             log.Message?.Contains("Failed to load feature flags", StringComparison.Ordinal) == true);
     }
-}
+}