Show detecting incorrect write order on SBE flyweight.

Adds a new schema and test, which is referenced from the SBE Warnings
page. The aim is to show how precedence checks in SBE `1.30.0` can help
prevent some incorrect usages of SBE flyweights.

Author: ZachBray

sbe-core/src/test/java/com/aeroncookbook/sbe/SbeTests.java

@@ -16,14 +16,16 @@
 
 package com.aeroncookbook.sbe;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
-import java.nio.ByteBuffer;
-
 import org.agrona.concurrent.UnsafeBuffer;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import java.lang.reflect.Field;
+import java.nio.ByteBuffer;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 public class SbeTests
 {
 
@@ -175,6 +177,32 @@ public void dataCanBeCorrupted()
         Assertions.assertNotEquals(DATA_2, decoder.data2());
     }
 
+    @Test
+    public void corruptionCanBeDetected() throws NoSuchFieldException, IllegalAccessException
+    {
+        assumePrecedenceChecksAreEnabled();
+
+        final SampleCorruptionDetectedEncoder encoder = new SampleCorruptionDetectedEncoder();
+        final MessageHeaderEncoder messageHeaderEncoder = new MessageHeaderEncoder();
+        final ByteBuffer byteBuffer = ByteBuffer.allocateDirect(128);
+        final UnsafeBuffer directBuffer = new UnsafeBuffer(byteBuffer);
+
+        encoder.wrapAndApplyHeader(directBuffer, 0, messageHeaderEncoder);
+        final IllegalStateException exception =
+            assertThrows(IllegalStateException.class, () -> encoder.data2(DATA_2));
+        final String expectedErrorFragment =
+            "Illegal field access order. Cannot access field \"data2\" in state: V0_BLOCK.";
+        Assertions.assertTrue(exception.getMessage().contains(expectedErrorFragment));
+    }
+
+    private static void assumePrecedenceChecksAreEnabled() throws NoSuchFieldException, IllegalAccessException
+    {
+        final Field enabledField = SampleCorruptionDetectedEncoder.class
+            .getDeclaredField("SBE_ENABLE_PRECEDENCE_CHECKS");
+        enabledField.setAccessible(true);
+        Assertions.assertTrue((boolean)enabledField.get(null));
+    }
+
     @Test
     public void dataCanBeReadCorrectlyWhenWrittenCorrectly()
     {

sbe-protocol/build.gradle.kts

@@ -35,7 +35,25 @@ tasks {
         outputs.dir(generatedDir)
     }
 
+    task("generateCodecsWithPrecedeceChecks", JavaExec::class) {
+        group = "sbe"
+        val codecsFile = "src/main/resources/precedence-checked-messages.xml"
+        val sbeFile = "src/main/resources/sbe/sbe.xsd"
+        inputs.files(codecsFile, sbeFile)
+        outputs.dir(generatedDir)
+        classpath = codecGeneration
+        mainClass.set("uk.co.real_logic.sbe.SbeTool")
+        args = listOf(codecsFile)
+        systemProperties["sbe.output.dir"] = generatedDir
+        systemProperties["sbe.target.language"] = "Java"
+        systemProperties["sbe.validation.xsd"] = sbeFile
+        systemProperties["sbe.validation.stop.on.error"] = "true"
+        systemProperties["sbe.generate.precedence.checks"] = "true"
+        outputs.dir(generatedDir)
+    }
+
     compileJava {
         dependsOn("generateCodecs")
+        dependsOn("generateCodecsWithPrecedeceChecks")
     }
 }

sbe-protocol/src/main/resources/precedence-checked-messages.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!--
+  ~ Copyright 2019-2023 Adaptive Financial Consulting Ltd.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~ https://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<sbe:messageSchema xmlns:sbe="http://fixprotocol.io/2016/sbe"
+                   package="com.aeroncookbook.sbe"
+                   id="689"
+                   version="1"
+                   semanticVersion="0.1"
+                   description="Sample SBE Messages"
+                   byteOrder="littleEndian">
+    <types>
+        <composite name="messageHeader" description="Message identifiers and length of message root">
+            <type name="blockLength" primitiveType="uint16"/>
+            <type name="templateId" primitiveType="uint16"/>
+            <type name="schemaId" primitiveType="uint16"/>
+            <type name="version" primitiveType="uint16"/>
+        </composite>
+        <composite name="varStringEncoding">
+            <type name="length" primitiveType="uint32" maxValue="1073741824"/>
+            <type name="varData" primitiveType="uint8" length="0" characterEncoding="UTF-8"/>
+        </composite>
+    </types>
+    <types>
+        <type name="Sequence" primitiveType="int64"/>
+    </types>
+
+    <sbe:message name="SampleCorruptionDetected" id="1002" description="Corruption sample">
+        <field name="sequence1" id="1" type="Sequence"/>
+        <field name="sequence2" id="2" type="Sequence"/>
+        <data name="data1" id="3" type="varStringEncoding"/>
+        <data name="data2" id="4" type="varStringEncoding"/>
+    </sbe:message>
+
+</sbe:messageSchema>