Merge pull request #754 from jeffgbutler/separate-empty-from-renderable

Refactoring Slice - Empty Conditions

Author: jeffgbutler

CHANGELOG.md

@@ -39,6 +39,9 @@ types - which is a rare usage. Please let us know if this causes an undo hardshi
    your code accordingly. ([#662](https://github.com/mybatis/mybatis-dynamic-sql/pull/662))
 2. Added the ability to code a bound value in rendered SQL. This is similar to a constant, but the value is added to
    the parameter map and a bind parameter marker is rendered. ([#738](https://github.com/mybatis/mybatis-dynamic-sql/pull/738))
+3. Refactored the conditions to separate the concept of an empty condition from that of a renderable condition. This
+   will enable a future change where conditions could decide to allow rendering even if they are considered empty (such
+   as rendering empty lists). This change should be transparent to users unless they have implemented custom conditions.
 
 ## Release 1.5.0 - April 21, 2023
 

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

@@ -35,8 +35,8 @@ public final <R> Stream<R> mapValues(Function<T, R> mapper) {
     }
 
     @Override
-    public boolean shouldRender() {
-        return !values.isEmpty();
+    public boolean isEmpty() {
+        return values.isEmpty();
     }
 
     @Override
@@ -56,20 +56,20 @@ private Collection<T> applyFilter(Predicate<? super T> predicate) {
 
     protected <S extends AbstractListValueCondition<T>> S filterSupport(Predicate<? super T> predicate,
             Function<Collection<T>, S> constructor, S self, Supplier<S> emptySupplier) {
-        if (shouldRender()) {
+        if (isEmpty()) {
+            return self;
+        } else {
             Collection<T> filtered = applyFilter(predicate);
             return filtered.isEmpty() ? emptySupplier.get() : constructor.apply(filtered);
-        } else {
-            return self;
         }
     }
 
     protected <R, S extends AbstractListValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper,
             Function<Collection<R>, S> constructor, Supplier<S> emptySupplier) {
-        if (shouldRender()) {
-            return constructor.apply(applyMapper(mapper));
-        } else {
+        if (isEmpty()) {
             return emptySupplier.get();
+        } else {
+            return constructor.apply(applyMapper(mapper));
         }
     }
 

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

@@ -27,10 +27,10 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
 
     protected <S extends AbstractNoValueCondition<?>> S filterSupport(BooleanSupplier booleanSupplier,
             Supplier<S> emptySupplier, S self) {
-        if (shouldRender()) {
-            return booleanSupplier.getAsBoolean() ? self : emptySupplier.get();
-        } else {
+        if (isEmpty()) {
             return self;
+        } else {
+            return booleanSupplier.getAsBoolean() ? self : emptySupplier.get();
         }
     }
 

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

@@ -37,19 +37,19 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
 
     protected <S extends AbstractSingleValueCondition<T>> S filterSupport(Predicate<? super T> predicate,
             Supplier<S> emptySupplier, S self) {
-        if (shouldRender()) {
-            return predicate.test(value) ? self : emptySupplier.get();
-        } else {
+        if (isEmpty()) {
             return self;
+        } else {
+            return predicate.test(value) ? self : emptySupplier.get();
         }
     }
 
     protected <R, S extends AbstractSingleValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper,
             Function<R, S> constructor, Supplier<S> emptySupplier) {
-        if (shouldRender()) {
-            return constructor.apply(mapper.apply(value));
-        } else {
+        if (isEmpty()) {
             return emptySupplier.get();
+        } else {
+            return constructor.apply(mapper.apply(value));
         }
     }
 

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

@@ -45,10 +45,10 @@ public <R> R accept(ConditionVisitor<T, R> visitor) {
 
     protected <S extends AbstractTwoValueCondition<T>> S filterSupport(BiPredicate<? super T, ? super T> predicate,
             Supplier<S> emptySupplier, S self) {
-        if (shouldRender()) {
-            return predicate.test(value1, value2) ? self : emptySupplier.get();
-        } else {
+        if (isEmpty()) {
             return self;
+        } else {
+            return predicate.test(value1, value2) ? self : emptySupplier.get();
         }
     }
 
@@ -59,10 +59,10 @@ protected <S extends AbstractTwoValueCondition<T>> S filterSupport(Predicate<? s
 
     protected <R, S extends AbstractTwoValueCondition<R>> S mapSupport(Function<? super T, ? extends R> mapper1,
             Function<? super T, ? extends R> mapper2, BiFunction<R, R, S> constructor, Supplier<S> emptySupplier) {
-        if (shouldRender()) {
-            return constructor.apply(mapper1.apply(value1), mapper2.apply(value2));
-        } else {
+        if (isEmpty()) {
             return emptySupplier.get();
+        } else {
+            return constructor.apply(mapper1.apply(value1), mapper2.apply(value2));
         }
     }
 

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

@@ -15,22 +15,34 @@
  */
 package org.mybatis.dynamic.sql;
 
+import org.mybatis.dynamic.sql.render.RenderingContext;
+
 @FunctionalInterface
 public interface VisitableCondition<T> {
     <R> R accept(ConditionVisitor<T, R> visitor);
 
     /**
      * Subclasses can override this to inform the renderer if the condition should not be included
-     * in the rendered SQL.  For example, IsEqualWhenPresent will not render if the value is null.
+     * in the rendered SQL.  Typically, conditions will not render if they are empty.
      *
      * @return true if the condition should render.
      */
-    default boolean shouldRender() {
-        return true;
+    default boolean shouldRender(RenderingContext renderingContext) {
+        return !isEmpty();
+    }
+
+    /**
+     * Subclasses can override this to indicate whether the condition is considered empty. This is primarily used in
+     * map and filter operations - the map and filter functions will not be applied if the condition is empty.
+     *
+     * @return true if the condition is empty.
+     */
+    default boolean isEmpty() {
+        return false;
     }
 
     /**
-     * This method will be called during rendering when {@link VisitableCondition#shouldRender()}
+     * This method will be called during rendering when {@link VisitableCondition#shouldRender(RenderingContext)}
      * returns false.
      */
     default void renderingSkipped() {}

src/main/java/org/mybatis/dynamic/sql/select/aggregate/Sum.java

@@ -36,7 +36,7 @@ private Sum(BindableColumn<T> column) {
     private Sum(BindableColumn<T> column, VisitableCondition<T> condition) {
         super(column);
         renderer = rc -> {
-            Validator.assertTrue(condition.shouldRender(), "ERROR.37", "sum"); //$NON-NLS-1$ //$NON-NLS-2$
+            Validator.assertTrue(condition.shouldRender(rc), "ERROR.37", "sum"); //$NON-NLS-1$ //$NON-NLS-2$
 
             DefaultConditionVisitor<T> visitor = new DefaultConditionVisitor.Builder<T>()
                     .withColumn(column)

src/main/java/org/mybatis/dynamic/sql/where/condition/IsBetween.java

@@ -25,8 +25,8 @@
 public class IsBetween<T> extends AbstractTwoValueCondition<T> {
     private static final IsBetween<?> EMPTY = new IsBetween<Object>(null, null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsEqualTo.java

@@ -24,8 +24,8 @@ public class IsEqualTo<T> extends AbstractSingleValueCondition<T> {
 
     private static final IsEqualTo<?> EMPTY = new IsEqualTo<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsGreaterThan.java

@@ -23,8 +23,8 @@
 public class IsGreaterThan<T> extends AbstractSingleValueCondition<T> {
     private static final IsGreaterThan<?> EMPTY = new IsGreaterThan<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsGreaterThanOrEqualTo.java

@@ -23,8 +23,8 @@
 public class IsGreaterThanOrEqualTo<T> extends AbstractSingleValueCondition<T> {
     private static final IsGreaterThanOrEqualTo<?> EMPTY = new IsGreaterThanOrEqualTo<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsLessThan.java

@@ -23,8 +23,8 @@
 public class IsLessThan<T> extends AbstractSingleValueCondition<T> {
     private static final IsLessThan<?> EMPTY = new IsLessThan<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsLessThanOrEqualTo.java

@@ -23,8 +23,8 @@
 public class IsLessThanOrEqualTo<T> extends AbstractSingleValueCondition<T> {
     private static final IsLessThanOrEqualTo<?> EMPTY = new IsLessThanOrEqualTo<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsLike.java

@@ -23,8 +23,8 @@
 public class IsLike<T> extends AbstractSingleValueCondition<T> {
     private static final IsLike<?> EMPTY = new IsLike<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsLikeCaseInsensitive.java

@@ -25,8 +25,8 @@ public class IsLikeCaseInsensitive extends AbstractSingleValueCondition<String>
         implements CaseInsensitiveVisitableCondition {
     private static final IsLikeCaseInsensitive EMPTY = new IsLikeCaseInsensitive(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotBetween.java

@@ -25,8 +25,8 @@
 public class IsNotBetween<T> extends AbstractTwoValueCondition<T> {
     private static final IsNotBetween<?> EMPTY = new IsNotBetween<Object>(null, null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotEqualTo.java

@@ -23,8 +23,8 @@
 public class IsNotEqualTo<T> extends AbstractSingleValueCondition<T> {
     private static final IsNotEqualTo<?> EMPTY = new IsNotEqualTo<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotLike.java

@@ -23,8 +23,8 @@
 public class IsNotLike<T> extends AbstractSingleValueCondition<T> {
     private static final IsNotLike<?> EMPTY = new IsNotLike<Object>(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotLikeCaseInsensitive.java

@@ -25,8 +25,8 @@ public class IsNotLikeCaseInsensitive extends AbstractSingleValueCondition<Strin
         implements CaseInsensitiveVisitableCondition {
     private static final IsNotLikeCaseInsensitive EMPTY = new IsNotLikeCaseInsensitive(null) {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNotNull.java

@@ -22,8 +22,8 @@
 public class IsNotNull<T> extends AbstractNoValueCondition<T> {
     private static final IsNotNull<?> EMPTY = new IsNotNull<Object>() {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

src/main/java/org/mybatis/dynamic/sql/where/condition/IsNull.java

@@ -22,8 +22,8 @@
 public class IsNull<T> extends AbstractNoValueCondition<T> {
     private static final IsNull<?> EMPTY = new IsNull<Object>() {
         @Override
-        public boolean shouldRender() {
-            return false;
+        public boolean isEmpty() {
+            return true;
         }
     };
 

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

@@ -110,7 +110,7 @@ public Optional<RenderedCriterion> render(List<AndOrCriteriaGroup> subCriteria,
     }
 
     private <T> Optional<FragmentAndParameters> renderColumnAndCondition(ColumnAndConditionCriterion<T> criterion) {
-        if (criterion.condition().shouldRender()) {
+        if (criterion.condition().shouldRender(renderingContext)) {
             return Optional.of(renderCondition(criterion));
         } else {
             criterion.condition().renderingSkipped();