Fix step state incorrect type when returning null from steps

inngest-spring-boot-demo/src/main/java/com/inngest/springbootdemo/testfunctions/ReturnNullStepFunction.java

@@ -0,0 +1,23 @@
+package com.inngest.springbootdemo.testfunctions;
+
+import com.inngest.FunctionContext;
+import com.inngest.InngestFunction;
+import com.inngest.InngestFunctionConfigBuilder;
+import com.inngest.Step;
+import org.jetbrains.annotations.NotNull;
+
+public class ReturnNullStepFunction extends InngestFunction {
+    @NotNull
+    @Override
+    public InngestFunctionConfigBuilder config(InngestFunctionConfigBuilder builder) {
+        return builder
+            .id("null-step-fn")
+            .name("Function that has a step that returns null")
+            .triggerEvent("test/return.null.step");
+    }
+
+    @Override
+    public String execute(FunctionContext ctx, Step step) {
+        return step.run("null", () -> null, String.class);
+    }
+}

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/DemoTestConfiguration.java

@@ -36,6 +36,7 @@ protected HashMap<String, InngestFunction> functions() {
         addInngestFunction(functions, new LoopFunction());
         addInngestFunction(functions, new CancelOnEventFunction());
         addInngestFunction(functions, new CancelOnMatchFunction());
+        addInngestFunction(functions, new ReturnNullStepFunction());
 
         return functions;
     }

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/ReturnNullStepIntegrationTest.java

@@ -0,0 +1,34 @@
+package com.inngest.springbootdemo;
+
+import com.inngest.Inngest;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.springframework.beans.factory.annotation.Autowired;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+
+@IntegrationTest
+@Execution(ExecutionMode.CONCURRENT)
+class ReturnNullStepIntegrationTest {
+    @Autowired
+    private DevServerComponent devServer;
+
+    @Autowired
+    private Inngest client;
+
+    @Test
+    void testReturnNullFromStep() throws Exception {
+        String eventId = InngestFunctionTestHelpers.sendEvent(client, "test/return.null.step").getIds()[0];
+
+        Thread.sleep(5000);
+
+        RunEntry<Object> run = devServer.runsByEvent(eventId).first();
+
+        assertEquals(eventId, run.getEvent_id());
+        assertEquals("Completed", run.getStatus());
+        assertNull(run.getOutput());
+    }
+}

inngest-test-server/src/main/kotlin/com/inngest/testserver/ImageFromPrompt.kt

@@ -12,36 +12,8 @@ class ImageFromPrompt : InngestFunction() {
     override fun execute(
         ctx: FunctionContext,
         step: Step,
-    ): String {
-        val imageURL =
-            try {
-                step.run("generate-image-dall-e") {
-                    // Call the DALL-E model to generate an image
-                    throw Exception("Failed to generate image")
-
-                    "example.com/image-dall-e.jpg"
-                }
-            } catch (e: StepError) {
-                // Fall back to a different image generation model
-                step.run("generate-image-midjourney") {
-                    // Call the MidJourney model to generate an image
-                    "example.com/image-midjourney.jpg"
-                }
-            }
-
-        try {
-            step.invoke<Map<String, Any>>(
-                "push-to-slack-channel",
-                "ktor-dev",
-                "PushToSlackChannel",
-                mapOf("image" to imageURL),
-                null,
-            )
-        } catch (e: StepError) {
-            // Pushing to Slack is not critical, so we can ignore the error, log it
-            // or handle it in some other way.
+    ): String? =
+        step.run("generate-image-dall-e") {
+            null as String?
         }
-
-        return imageURL
-    }
 }

inngest/src/main/kotlin/com/inngest/State.kt

@@ -2,6 +2,7 @@ package com.inngest
 
 import com.fasterxml.jackson.databind.JsonNode
 import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.node.NullNode
 import com.fasterxml.jackson.databind.node.ObjectNode
 import java.security.MessageDigest
 
@@ -60,16 +61,13 @@ class State(
         val node: JsonNode = mapper.readTree(payloadJson)
         val stepResult = node.path("steps").get(hashedId) ?: throw StateNotFound()
 
-        if (stepResult.has(fieldName)) {
-            return deserializeStepData(stepResult.get(fieldName), type)
-        } else if (stepResult.has("error")) {
-            val error = mapper.treeToValue(stepResult.get("error"), StepError::class.java)
-            throw error
+        return when {
+            stepResult.has(fieldName) -> deserializeStepData(stepResult.get(fieldName), type)
+            stepResult.has("error") -> throw mapper.treeToValue(stepResult.get("error"), StepError::class.java)
+            // NOTE - Sleep steps will be stored as null
+            stepResult is NullNode -> null
+            else -> throw Exception("Unexpected step data structure")
         }
-        // NOTE - Sleep steps will be stored as null
-        // TODO - Investigate if sendEvents stores null as well.
-        // TODO - Check the state is actually null
-        return null
     }
 
     private fun <T> deserializeStepData(

inngest/src/main/kotlin/com/inngest/Step.kt

@@ -102,10 +102,7 @@ class Step(
         val hashedId = state.getHashFromId(id)
 
         try {
-            val stepResult = state.getState(hashedId, type)
-            if (stepResult != null) {
-                return stepResult
-            }
+            return state.getState(hashedId, type) as T
         } catch (e: StateNotFound) {
             // If there is no existing result, run the lambda
             executeStep(id, hashedId, fn)