Fix staged builders for single component records (#179)

Fixes #177

Author: Randgalt

record-builder-processor/src/main/java/io/soabase/recordbuilder/processor/InternalRecordBuilderProcessor.java

@@ -196,10 +196,6 @@ private void addOnceOnlySupport() {
     }
 
     private void addStagedBuilderClasses() {
-        if (recordComponents.size() < 2) {
-            return;
-        }
-
         IntStream.range(0, recordComponents.size()).forEach(index -> {
             Optional<RecordClassType> nextComponent = ((index + 1) < recordComponents.size())
                     ? Optional.of(recordComponents.get(index + 1)) : Optional.empty();
@@ -723,10 +719,6 @@ private void addStaticDefaultBuilderMethod() {
     }
 
     private void addStaticStagedBuilderMethod(String builderMethodName) {
-        if (recordComponents.size() < 2) {
-            return;
-        }
-
         /*
          * Adds the staged builder method similar to:
          *
@@ -757,11 +749,12 @@ private void addStaticStagedBuilderMethod(String builderMethodName) {
             codeBlock.addStatement(")");
         }
 
+        var returnType = stagedBuilderType(recordComponents.isEmpty() ? builderClassType : recordComponents.get(0));
+
         var methodSpec = MethodSpec.methodBuilder(builderMethodName)
                 .addJavadoc("Return the first stage of a staged builder\n")
                 .addModifiers(Modifier.PUBLIC, Modifier.STATIC).addAnnotation(generatedRecordBuilderAnnotation)
-                .addTypeVariables(typeVariables).returns(stagedBuilderType(recordComponents.get(0)).typeName())
-                .addCode(codeBlock.build()).build();
+                .addTypeVariables(typeVariables).returns(returnType.typeName()).addCode(codeBlock.build()).build();
         builder.addMethod(methodSpec);
     }
 

record-builder-test/src/main/java/io/soabase/recordbuilder/test/staged/NoFieldsStaged.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 The original author or authors
+ *
+ * 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
+ *
+ * http://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.
+ */
+package io.soabase.recordbuilder.test.staged;
+
+import io.soabase.recordbuilder.core.RecordBuilder;
+
+@RecordBuilder
+@RecordBuilder.Options(builderMode = RecordBuilder.BuilderMode.STAGED)
+public record NoFieldsStaged() {
+}

record-builder-test/src/main/java/io/soabase/recordbuilder/test/staged/SingleFieldStaged.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2019 The original author or authors
+ *
+ * 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
+ *
+ * http://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.
+ */
+package io.soabase.recordbuilder.test.staged;
+
+import io.soabase.recordbuilder.core.RecordBuilder;
+
+import java.time.Instant;
+
+@RecordBuilder
+@RecordBuilder.Options(builderMode = RecordBuilder.BuilderMode.STAGED)
+public record SingleFieldStaged(int i) {
+}

record-builder-test/src/test/java/io/soabase/recordbuilder/test/staged/TestStagedBuilder.java

@@ -61,4 +61,16 @@ void testGenericCombined() {
                 .aT(new GenericStaged<>("other", builder.build(), BigInteger.TEN)).theUThing(BigDecimal.ONE).build();
         assertEquals(obj1, obj2);
     }
+
+    @Test
+    void testSingleField() {
+        SingleFieldStaged obj = SingleFieldStagedBuilder.builder().i(1).build();
+        assertEquals(new SingleFieldStaged(1), obj);
+    }
+
+    @Test
+    void testNoFields() {
+        NoFieldsStaged obj = NoFieldsStagedBuilder.builder().build();
+        assertEquals(new NoFieldsStaged(), obj);
+    }
 }