fix(S1155): return empty check for collections whose size < 1 (#1026)

sorald/src/main/java/sorald/processor/CollectionIsEmptyProcessor.java

@@ -22,8 +22,23 @@ protected void repairInternal(CtBinaryOperator<?> element) {
                         .orElseThrow(IllegalStateException::new);
         CtInvocation<?> newInvocation =
                 getFactory().createInvocation(methodCallTarget, isEmptyMethod.getReference());
-        CtExpression<?> expression =
-                element.getKind() == BinaryOperatorKind.EQ ? newInvocation : not(newInvocation);
+        CtExpression<?> expression = getIsEmptyInvocation(newInvocation, element);
         element.replace(expression);
     }
+
+    /**
+     * Returns the invocation of isEmpty() that should be used to replace the given element. If the
+     * operator is == or < 1, then we can just return the invocation, otherwise we need to negate
+     * it.
+     */
+    private CtExpression<?> getIsEmptyInvocation(
+            CtInvocation<?> invocation, CtBinaryOperator<?> element) {
+        if (element.getKind() == BinaryOperatorKind.EQ) {
+            return invocation;
+        } else if (element.getKind() == BinaryOperatorKind.LT
+                && element.getRightHandOperand().equals(getFactory().createLiteral(1))) {
+            return invocation;
+        }
+        return not(invocation);
+    }
 }

sorald/src/main/java/sorald/processor/CollectionIsEmptyProcessor.md

@@ -9,4 +9,10 @@ Example:
 ...
 - if (myCollection.size() != 0) {  // Noncompliant
 + if (!myCollection.isEmpty()) {
+...
+- if (myCollection.size() < 1) {  // Noncompliant
++ if (myCollection.isEmpty()) {
 ```
+
+> We ignore expressions such as `0 == myCollections.size()` based on heuristics
+> that it is not a common practice to do so.

sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/CollectionIsEmpty.java → sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/EqualTo.java

@@ -1,6 +1,6 @@
 import java.util.Collection;
 
-public class CollectionIsEmpty {
+public class EqualTo {
     public static void main(String[] args) {
         Collection myCollection = null;
 

sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/CollectionIsEmpty.java.expected → sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/EqualTo.java.expected

@@ -1,6 +1,6 @@
 import java.util.Collection;
 
-public class CollectionIsEmpty {
+public class EqualTo {
     public static void main(String[] args) {
         Collection myCollection = null;
 

sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/LessThan.java

@@ -0,0 +1,11 @@
+import java.util.Collection;
+
+public class LessThan {
+    public static void main(String[] args) {
+        Collection myCollection = null;
+
+        if (myCollection.size() < 1) {  // Noncompliant
+            /* ... */
+        }
+    }
+}

sorald/src/test/resources/processor_test_files/S1155_CollectionIsEmpty/LessThan.java.expected

@@ -0,0 +1,11 @@
+import java.util.Collection;
+
+public class LessThan {
+    public static void main(String[] args) {
+        Collection myCollection = null;
+
+        if (myCollection.isEmpty()) {
+            /* ... */
+        }
+    }
+}