fix(projections): harden js state handling

src/EventStore.Projections.Core.Tests/Services/Jint/Serialization/when_serializing_state.cs

@@ -136,6 +136,15 @@ public void undefined()
 		Assert.AreEqual(@"null", serialized);
 	}
 
+	[TestCase("NaN")]
+	[TestCase("Infinity")]
+	[TestCase("-Infinity")]
+	public void non_finite_numbers_are_serialized_as_null(string expression)
+	{
+		var serialized = _sut.Serialize(_engine.Evaluate(expression));
+		Assert.AreEqual(@"null", serialized);
+	}
+
 	[Test]
 	public void undefined_property()
 	{

src/EventStore.Projections.Core.Tests/Services/Jint/when_accessing_event_body_with_non_object_data.cs

@@ -0,0 +1,35 @@
+using System;
+using EventStore.Projections.Core.Services;
+using EventStore.Projections.Core.Services.Processing.Checkpointing;
+using NUnit.Framework;
+
+namespace EventStore.Projections.Core.Tests.Services.Jint;
+
+[TestFixture]
+public class when_accessing_event_body_with_non_object_data : TestFixtureWithInterpretedProjection
+{
+	protected override void Given()
+	{
+		_projection = @"
+                fromAll().when({$any:
+                    function(state, event) {
+                        return event.body;
+                    }
+                });
+            ";
+	}
+
+	[TestCase("null", null)]
+	[TestCase("42", "42")]
+	[TestCase(@"""hello""", @"""hello""")]
+	[TestCase("true", "true")]
+	[Category(_projectionType)]
+	public void process_event_returns_json_primitive_body(string data, string expectedState)
+	{
+		_stateHandler.ProcessEvent(
+			"", CheckpointTag.FromPosition(0, 20, 10), "stream1", "type1", "category", Guid.NewGuid(), 0,
+			"metadata", data, out var state, out _);
+
+		Assert.AreEqual(expectedState, state);
+	}
+}

src/EventStore.Projections.Core.Tests/Services/Jint/when_round_tripping_js_projection_with_string_state.cs

@@ -0,0 +1,63 @@
+using System;
+using EventStore.Projections.Core.Services;
+using EventStore.Projections.Core.Services.Processing.Checkpointing;
+using NUnit.Framework;
+
+namespace EventStore.Projections.Core.Tests.Services.Jint;
+
+[TestFixture]
+public class when_round_tripping_js_projection_with_string_state : TestFixtureWithInterpretedProjection
+{
+	protected override void Given()
+	{
+		_projection = @"
+                fromAll().when({
+                    type1: function(state, event) {
+                        return 'hello';
+                    }
+                });
+            ";
+	}
+
+	[Test, Category(_projectionType)]
+	public void process_event_returns_json_encoded_string_state()
+	{
+		_stateHandler.ProcessEvent(
+			"", CheckpointTag.FromPosition(0, 20, 10), "stream1", "type1", "category", Guid.NewGuid(), 0,
+			"metadata", @"{""a"":""b""}", out var state, out _);
+
+		Assert.AreEqual(@"""hello""", state);
+		Assert.DoesNotThrow(() => _stateHandler.Load(state));
+	}
+}
+
+[TestFixture]
+public class when_round_tripping_bi_state_js_projection_with_string_state : TestFixtureWithInterpretedProjection
+{
+	protected override void Given()
+	{
+		_projection = @"
+                options({
+                    biState: true,
+                });
+                fromAll().foreachStream().when({
+                    type1: function(state, event) {
+                        state[0] = 'hello';
+                        return state;
+                    }
+                });
+            ";
+	}
+
+	[Test, Category(_projectionType)]
+	public void process_event_returns_json_encoded_string_state()
+	{
+		_stateHandler.ProcessEvent(
+			"", CheckpointTag.FromPosition(0, 20, 10), "stream1", "type1", "category", Guid.NewGuid(), 0,
+			"metadata", @"{""a"":""b""}", out var state, out var sharedState, out _);
+
+		Assert.AreEqual(@"""hello""", state);
+		Assert.IsNull(sharedState);
+		Assert.DoesNotThrow(() => _stateHandler.Load(state));
+	}
+}

src/EventStore.Projections.Core/Services/Interpreted/JintProjectionStateHandler.cs

@@ -243,14 +243,7 @@ private void PrepareOutput(out string? newState, out string? newSharedState, out
 				var arr = _state.AsArray();
 				if (arr.TryGetValue(0, out var state))
 				{
-					if (_state.IsString())
-					{
-						newState = _state.AsString();
-					}
-					else
-					{
-						newState = ConvertToStringHandlingNulls(state);
-					}
+					newState = ConvertToStringHandlingNulls(state);
 				}
 				else
 				{
@@ -267,11 +260,6 @@ private void PrepareOutput(out string? newState, out string? newSharedState, out
 				}
 
 			}
-			else if (_state.IsString())
-			{
-				newState = _state.AsString();
-				newSharedState = null;
-			}
 			else
 			{
 				newState = ConvertToStringHandlingNulls(_state);
@@ -921,7 +909,7 @@ public JsValue Handle(JsValue state, EventEnvelope eventEnvelope)
 				}
 				else
 				{
-					newState = eventEnvelope.BodyRaw;
+					newState = eventEnvelope.IsJson ? eventEnvelope.Body : eventEnvelope.BodyRaw;
 				}
 				return newState == Undefined ? state : newState;
 			}
@@ -1096,33 +1084,32 @@ public JsValue Body
 			{
 				get
 				{
-					if (TryGetValue("body", out var value) && value is ObjectInstance oi)
+					if (TryGetValue("body", out var value) && value is not JsUndefined)
 					{
-						return oi;
+						return value;
 					}
 
-					if (EnsureBody(out JsValue objectInstance))
+					if (EnsureBody(out var body))
 					{
-						return objectInstance;
+						return body;
 					}
 
 					return Undefined;
 				}
 			}
 
-			private bool EnsureBody(out JsValue objectInstance)
+			private bool EnsureBody(out JsValue body)
 			{
 				if (IsJson && TryGetValue("bodyRaw", out var raw) && raw is not JsUndefined)
 				{
-					var body = raw.IsNull() ? raw : _parser.Parse(raw.AsString());
+					body = raw.IsNull() ? raw : _parser.Parse(raw.AsString());
 					var pd = new PropertyDescriptor(body, false, true, false);
 					SetOwnProperty("body", pd);
 					SetOwnProperty("data", pd);
-					objectInstance = (ObjectInstance)body;
 					return true;
 				}
 
-				objectInstance = Undefined;
+				body = Undefined;
 				return false;
 			}
 
@@ -1555,7 +1542,15 @@ static void SerializePrimitive(JsValue value, Utf8JsonWriter writer)
 
 						break;
 					case Types.Number:
-						writer.WriteNumberValue(value.AsNumber());
+						var number = value.AsNumber();
+						if (double.IsFinite(number))
+						{
+							writer.WriteNumberValue(number);
+						}
+						else
+						{
+							writer.WriteNullValue();
+						}
 						break;
 					case Types.BigInt:
 						writer.WriteStringValue(value.ToString());