Move list rendering decision fully withing the list condition

This also removes some Optional silliness from the visitor

Author: jeffgbutler

src/main/java/org/mybatis/dynamic/sql/AbstractListValueCondition.java

@@ -25,7 +25,7 @@
 public abstract class AbstractListValueCondition<T> implements VisitableCondition<T> {
     protected Collection<T> values;
     protected UnaryOperator<Stream<T>> valueStreamTransformer;
-    protected boolean skipRenderingWhenEmpty = true;
+    protected boolean renderWhenEmpty = false;
 
     protected AbstractListValueCondition(Collection<T> values) {
         this(values, UnaryOperator.identity());
@@ -40,15 +40,16 @@ public final <R> Stream<R> mapValues(Function<T, R> mapper) {
         return valueStreamTransformer.apply(values.stream()).map(mapper);
     }
 
-    public boolean skipRenderingWhenEmpty() {
-        return skipRenderingWhenEmpty;
+    @Override
+    public boolean shouldRender() {
+        return !values.isEmpty() || renderWhenEmpty;
     }
-    
+
     /**
      * Use with caution - this could cause the library to render invalid SQL like "where column in ()".
      */
     protected void forceRenderingWhenEmpty() {
-        skipRenderingWhenEmpty = false;
+        renderWhenEmpty = true;
     }
 
     @Override

src/main/java/org/mybatis/dynamic/sql/util/FragmentCollector.java

@@ -57,10 +57,6 @@ public boolean hasMultipleFragments() {
         return fragments.size() > 1;
     }
 
-    public boolean isEmpty() {
-        return fragments.isEmpty();
-    }
-    
     public static Collector<FragmentAndParameters, FragmentCollector, FragmentCollector> collect() {
         return Collector.of(FragmentCollector::new,
                 FragmentCollector::add,

src/main/java/org/mybatis/dynamic/sql/where/render/CriterionRenderer.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2016-2018 the original author or authors.
+ *    Copyright 2016-2020 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.
@@ -77,7 +77,7 @@ private Optional<FragmentAndParameters> renderCondition() {
                 .withTableAliasCalculator(tableAliasCalculator)
                 .withParameterName(parameterName)
                 .build();
-        return sqlCriterion.condition().accept(visitor);
+        return Optional.of(sqlCriterion.condition().accept(visitor));
     }
 
     public static <T> Builder<T> withCriterion(SqlCriterion<T> sqlCriterion) {

src/main/java/org/mybatis/dynamic/sql/where/render/WhereConditionVisitor.java

@@ -16,7 +16,6 @@
 package org.mybatis.dynamic.sql.where.render;
 
 import java.util.Objects;
-import java.util.Optional;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.mybatis.dynamic.sql.AbstractColumnComparisonCondition;
@@ -34,7 +33,7 @@
 import org.mybatis.dynamic.sql.util.FragmentAndParameters;
 import org.mybatis.dynamic.sql.util.FragmentCollector;
 
-public class WhereConditionVisitor<T> implements ConditionVisitor<T, Optional<FragmentAndParameters>> {
+public class WhereConditionVisitor<T> implements ConditionVisitor<T, FragmentAndParameters> {
 
     private RenderingStrategy renderingStrategy;
     private AtomicInteger sequence;
@@ -51,38 +50,34 @@ private WhereConditionVisitor(Builder<T> builder) {
     }
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractListValueCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractListValueCondition<T> condition) {
         FragmentCollector fc = condition.mapValues(this::toFragmentAndParameters)
                 .collect(FragmentCollector.collect());
 
-        if (fc.isEmpty() && condition.skipRenderingWhenEmpty()) {
-            return Optional.empty();
-        }
-        
         return FragmentAndParameters.withFragment(condition.renderCondition(columnName(), fc.fragments()))
                 .withParameters(fc.parameters())
-                .buildOptional();
+                .build();
     }
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractNoValueCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractNoValueCondition<T> condition) {
         return FragmentAndParameters.withFragment(condition.renderCondition(columnName()))
-                .buildOptional();
+                .build();
     }
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractSingleValueCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractSingleValueCondition<T> condition) {
         String mapKey = RenderingStrategy.formatParameterMapKey(sequence);
         String fragment = condition.renderCondition(columnName(),
                 getFormattedJdbcPlaceholder(mapKey));
 
         return FragmentAndParameters.withFragment(fragment)
                 .withParameter(mapKey, convertValue(condition.value()))
-                .buildOptional();
+                .build();
     }
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractTwoValueCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractTwoValueCondition<T> condition) {
         String mapKey1 = RenderingStrategy.formatParameterMapKey(sequence);
         String mapKey2 = RenderingStrategy.formatParameterMapKey(sequence);
         String fragment = condition.renderCondition(columnName(),
@@ -92,12 +87,12 @@ public Optional<FragmentAndParameters> visit(AbstractTwoValueCondition<T> condit
         return FragmentAndParameters.withFragment(fragment)
                 .withParameter(mapKey1, convertValue(condition.value1()))
                 .withParameter(mapKey2, convertValue(condition.value2()))
-                .buildOptional();
+                .build();
     }
 
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractSubselectCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractSubselectCondition<T> condition) {
         SelectStatementProvider selectStatement = SelectRenderer.withSelectModel(condition.selectModel())
                 .withRenderingStrategy(renderingStrategy)
                 .withSequence(sequence)
@@ -108,13 +103,13 @@ public Optional<FragmentAndParameters> visit(AbstractSubselectCondition<T> condi
 
         return FragmentAndParameters.withFragment(fragment)
                 .withParameters(selectStatement.getParameters())
-                .buildOptional();
+                .build();
     }
 
     @Override
-    public Optional<FragmentAndParameters> visit(AbstractColumnComparisonCondition<T> condition) {
+    public FragmentAndParameters visit(AbstractColumnComparisonCondition<T> condition) {
         String fragment = condition.renderCondition(columnName(), tableAliasCalculator);
-        return FragmentAndParameters.withFragment(fragment).buildOptional();
+        return FragmentAndParameters.withFragment(fragment).build();
     }
 
     private Object convertValue(T value) {