Fix message in generated exceptions when the message field has a different casing

Author: adwsingh

codegen/codegen-core/src/it/java/software/amazon/smithy/java/codegen/test/ExceptionsTest.java

@@ -18,6 +18,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
 import software.amazon.smithy.java.codegen.test.model.EmptyException;
+import software.amazon.smithy.java.codegen.test.model.ExceptionWithCapitalMessage;
 import software.amazon.smithy.java.codegen.test.model.ExceptionWithExtraStringException;
 import software.amazon.smithy.java.codegen.test.model.OptionalMessageException;
 import software.amazon.smithy.java.codegen.test.model.SimpleException;
@@ -90,6 +91,12 @@ void explicitDisableStackTraceCapture() {
         }
     }
 
+    @Test
+    void testMessageMemberCapital() {
+        var exception = ExceptionWithCapitalMessage.builder().message("OOOPS!").build();
+        assertThat(exception.getMessage()).isEqualTo("OOOPS!");
+    }
+
     private static Throwable getCauseThrowable() {
         return new Throwable();
     }

codegen/codegen-core/src/it/resources/META-INF/smithy/exceptions/exception-tests.smithy

@@ -14,6 +14,7 @@ operation Exceptions {
         SimpleException
         EmptyException
         OptionalMessageException
+        ExceptionWithCapitalMessage
     ]
 }
 
@@ -25,6 +26,12 @@ structure ExceptionWithExtraStringException {
     extra: String
 }
 
+@error("server")
+structure ExceptionWithCapitalMessage {
+    @required
+    Message: String
+}
+
 @error("server")
 structure SimpleException {
     @required

codegen/codegen-core/src/main/java/software/amazon/smithy/java/codegen/generators/StructureGenerator.java

@@ -214,7 +214,12 @@ public void run() {
                                 // Here just in case we ever expand this trait.
                                 writer.putContext("errorFaultType", "OTHER");
                             }
-                            if (shape.getMember("message").isPresent()) {
+                            boolean isMessagePresent = shape.getAllMembers()
+                                    .values()
+                                    .stream()
+                                    .map(symbolProvider::toMemberName)
+                                    .anyMatch("message"::equals);
+                            if (isMessagePresent) {
                                 writer.write(
                                         "super($$SCHEMA, builder.message, builder.$$cause, ${errorFault:T}.${errorFaultType:L}, builder.$$captureStackTrace, builder.$$deserialized);");
                             } else {