NPE in COMPLEX_BOOLEAN_EXPRESSION rule

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/constants/Warnings.kt

@@ -115,7 +115,7 @@ enum class Warnings(
     WRONG_NEWLINES(true, "3.6.2", "incorrect line breaking"),
     TRAILING_COMMA(true, "3.6.2", "use trailing comma"),
     COMPLEX_EXPRESSION(false, "3.6.3", "complex dot qualified expression should be replaced with variable"),
-    COMPLEX_BOOLEAN_EXPRESSION(true, "3.6.4", "too complex boolean expression, that can be simplified"),
+    COMPLEX_BOOLEAN_EXPRESSION(true, "3.6.4", "simplification could be produced for the too complex boolean expression"),
 
     // FixMe: autofixing will be added for this rule
     STRING_CONCATENATION(true, "3.15.1", "strings should not be concatenated using plus operator - use string templates instead if the statement fits one line"),

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/chapter3/BooleanExpressionsRule.kt

@@ -159,8 +159,13 @@ class BooleanExpressionsRule(configRules: List<RulesConfig>) : DiktatRule(
             .toString()
             .replace("&", "&&")
             .replace("|", "||")
-            .drop(1)  // dropping first (
-            .dropLast(1)  // dropping last )
+
+        if (simplifiedExpr.toString().first() == '(' && simplifiedExpr.toString().last() == ')') {
+            correctKotlinBooleanExpression = correctKotlinBooleanExpression
+                .drop(1)
+                .dropLast(1)
+        }
+
         mapOfExpressionToChar.forEach { (key, value) ->
             correctKotlinBooleanExpression = correctKotlinBooleanExpression.replace(value.toString(), key)
         }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/BooleanExpressionsRuleFixTest.kt

@@ -19,4 +19,10 @@ class BooleanExpressionsRuleFixTest : FixTestBase("test/paragraph3/boolean_expre
     fun `check distributive law fixing`() {
         fixAndCompare("DistributiveLawExpected.kt", "DistributiveLawTest.kt")
     }
+
+    @Test
+    @Tag(WarningNames.COMPLEX_BOOLEAN_EXPRESSION)
+    fun `check same expressions`() {
+        fixAndCompare("SameExpressionsInConditionExpected.kt", "SameExpressionsInConditionTest.kt")
+    }
 }

diktat-rules/src/test/resources/test/paragraph3/boolean_expressions/SameExpressionsInConditionExpected.kt

@@ -0,0 +1,11 @@
+fun foo() {
+    if (a) {}
+    if (a) {}
+    if (a) {}
+
+    return if (node is TomlKeyValueSimple) {
+        decodeValue().toString().toLowerCase() != "null"
+    } else {
+        true
+    }
+}

diktat-rules/src/test/resources/test/paragraph3/boolean_expressions/SameExpressionsInConditionTest.kt

@@ -0,0 +1,11 @@
+fun foo() {
+    if (a || a) {}
+    if (a && a) {}
+    if ((((a && a)))) {}
+
+    return if ((node is TomlKeyValueSimple) || (node is TomlKeyValueSimple)) {
+        decodeValue().toString().toLowerCase() != "null"
+    } else {
+        true
+    }
+}