#428 - fixes inconsistent equals behavior (#430)

Author: uklimaschewski

src/main/java/com/ezylang/evalex/operators/booleans/InfixEqualsOperator.java

@@ -30,12 +30,12 @@ public class InfixEqualsOperator extends AbstractOperator {
   @Override
   public EvaluationValue evaluate(
       Expression expression, Token operatorToken, EvaluationValue... operands) {
+    if (operands[0].getDataType() != operands[1].getDataType()) {
+      return EvaluationValue.booleanValue(false);
+    }
     if (operands[0].isNullValue() && operands[1].isNullValue()) {
       return EvaluationValue.booleanValue(true);
     }
-    if (operands[0].isNullValue() || operands[1].isNullValue()) {
-      return EvaluationValue.booleanValue(false);
-    }
     return expression.convertValue(operands[0].compareTo(operands[1]) == 0);
   }
 }

src/main/java/com/ezylang/evalex/operators/booleans/InfixNotEqualsOperator.java

@@ -30,12 +30,12 @@ public class InfixNotEqualsOperator extends AbstractOperator {
   @Override
   public EvaluationValue evaluate(
       Expression expression, Token operatorToken, EvaluationValue... operands) {
+    if (operands[0].getDataType() != operands[1].getDataType()) {
+      return EvaluationValue.booleanValue(true);
+    }
     if (operands[0].isNullValue() && operands[1].isNullValue()) {
       return EvaluationValue.booleanValue(false);
     }
-    if (operands[0].isNullValue() || operands[1].isNullValue()) {
-      return EvaluationValue.booleanValue(true);
-    }
     return expression.convertValue(operands[0].compareTo(operands[1]) != 0);
   }
 }

src/test/java/com/ezylang/evalex/operators/booleans/InfixEqualsOperatorTest.java

@@ -54,6 +54,26 @@ void testInfixEqualsLiterals(String expression, String expectedResult)
     assertExpressionHasExpectedResult(expression, expectedResult);
   }
 
+  @ParameterizedTest
+  @CsvSource(
+      delimiter = ':',
+      value = {
+        "1==\"1\" : false",
+        "\"1\"==1 : false",
+        "true==\"1\" : false",
+        "\"1\"==true : false",
+        "false==\"1\" : false",
+        "\"1\"==false : false",
+        "DT_DATE_NEW(2022,10,30)==1 : false",
+        "1==DT_DATE_NEW(2022,10,30) : false",
+        "DT_DURATION_PARSE(\"PT24H\")==1 : false",
+        "1==DT_DURATION_PARSE(\"PT24H\") : false",
+      })
+  void testInfixEqualsTypesDiffer(String expression, String expectedResult)
+      throws EvaluationException, ParseException {
+    assertExpressionHasExpectedResult(expression, expectedResult);
+  }
+
   @Test
   void testInfixEqualsVariables() throws EvaluationException, ParseException {
     Expression expression = new Expression("a=b");

src/test/java/com/ezylang/evalex/operators/booleans/InfixNotEqualsOperatorTest.java

@@ -54,6 +54,26 @@ void testInfixNotEqualsLiterals(String expression, String expectedResult)
     assertExpressionHasExpectedResult(expression, expectedResult);
   }
 
+  @ParameterizedTest
+  @CsvSource(
+      delimiter = ':',
+      value = {
+        "1!=\"1\" : true",
+        "\"1\"!=1 : true",
+        "true!=\"1\" : true",
+        "\"1\"!=true : true",
+        "false!=\"1\" : true",
+        "\"1\"!=false : true",
+        "DT_DATE_NEW(2022,10,30)!=1 : true",
+        "1!=DT_DATE_NEW(2022,10,30) : true",
+        "DT_DURATION_PARSE(\"PT24H\")!=1 : true",
+        "1!=DT_DURATION_PARSE(\"PT24H\") : true",
+      })
+  void testInfixNotEqualsTypesDiffer(String expression, String expectedResult)
+      throws EvaluationException, ParseException {
+    assertExpressionHasExpectedResult(expression, expectedResult);
+  }
+
   @Test
   void testInfixNotEqualsVariables() throws EvaluationException, ParseException {
     Expression expression = new Expression("a!=b");