Fix hashing step ids in loops

Per https://github.com/inngest/inngest/blob/main/docs/SDK_SPEC.md#512-ids-and-hashing,
add `:n` starting with `:1` for repeated instances of a step id

Mostly similar to inngest-js implementation
https://github.com/inngest/inngest-js/blob/79069e1a3d700624ce49b323922c113fc952bcc6/packages/inngest/src/components/execution/v1.ts#L819-L831

The inngest-js SDK currently optionally warns of parallel indexing, but
this isn't in scope for beta so I left it out

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

@@ -0,0 +1,32 @@
+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 LoopFunction extends InngestFunction {
+
+    @NotNull
+    @Override
+    public InngestFunctionConfigBuilder config(InngestFunctionConfigBuilder builder) {
+        return builder
+            .id("loop-fn")
+            .name("Loop Function")
+            .triggerEvent("test/loop");
+    }
+
+
+    @Override
+    public Integer execute(FunctionContext ctx, Step step) {
+        int runningCount = 10;
+        for (int i = 0; i < 5; i++) {
+            int effectivelyFinalVariableForLambda = runningCount;
+            runningCount = step.run("add-ten", () -> effectivelyFinalVariableForLambda + 10, Integer.class);
+        }
+
+        return runningCount;
+    }
+}
+

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

@@ -24,6 +24,7 @@ protected HashMap<String, InngestFunction> functions() {
         addInngestFunction(functions, new InvokeFailureFunction());
         addInngestFunction(functions, new TryCatchRunFunction());
         addInngestFunction(functions, new ThrottledFunction());
+        addInngestFunction(functions, new LoopFunction());
 
         return functions;
     }

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

@@ -0,0 +1,30 @@
+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;
+
+@IntegrationTest
+@Execution(ExecutionMode.CONCURRENT)
+class LoopFunctionIntegrationTest {
+    @Autowired
+    private DevServerComponent devServer;
+
+    @Autowired
+    private Inngest client;
+
+    @Test
+    void testStepsInLoopExecuteCorrectly() throws Exception {
+        String loopEvent = InngestFunctionTestHelpers.sendEvent(client, "test/loop").first();
+        Thread.sleep(2000);
+
+        RunEntry<Object> loopRun = devServer.runsByEvent(loopEvent).first();
+        assertEquals("Completed", loopRun.getStatus());
+
+        assertEquals(60, loopRun.getOutput());
+    }
+}

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

@@ -9,8 +9,17 @@ class StateNotFound : Throwable("State not found for id")
 class State(
     private val payloadJson: String,
 ) {
+    private val stepIds = mutableSetOf<String>()
+
     fun getHashFromId(id: String): String {
-        val bytes = id.toByteArray(Charsets.UTF_8)
+        val idToHash: String =
+            if (id in stepIds) {
+                findNextAvailableStepId(id)
+            } else {
+                id
+            }
+        stepIds.add(idToHash)
+        val bytes = idToHash.toByteArray(Charsets.UTF_8)
         val digest = MessageDigest.getInstance("SHA-1")
         val hashedBytes = digest.digest(bytes)
         val sb = StringBuilder()
@@ -20,6 +29,20 @@ class State(
         return sb.toString()
     }
 
+    private fun findNextAvailableStepId(id: String): String {
+        var stepNumber = 1
+        var possibleStepId: String
+        while (true) {
+            possibleStepId = "$id:$stepNumber"
+            if (possibleStepId !in stepIds) {
+                break
+            }
+            stepNumber++
+        }
+
+        return possibleStepId
+    }
+
     inline fun <reified T> getState(
         hashedId: String,
         fieldName: String = "data",