Bugfix of NPE in complex binary expressions in long line rule

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

@@ -30,6 +30,7 @@ import com.pinterest.ktlint.core.ast.ElementType.KDOC_TEXT
 import com.pinterest.ktlint.core.ast.ElementType.LITERAL_STRING_TEMPLATE_ENTRY
 import com.pinterest.ktlint.core.ast.ElementType.LONG_STRING_TEMPLATE_ENTRY
 import com.pinterest.ktlint.core.ast.ElementType.LPAR
+import com.pinterest.ktlint.core.ast.ElementType.NULL
 import com.pinterest.ktlint.core.ast.ElementType.OPERATION_REFERENCE
 import com.pinterest.ktlint.core.ast.ElementType.PACKAGE_DIRECTIVE
 import com.pinterest.ktlint.core.ast.ElementType.PARENTHESIZED
@@ -177,12 +178,15 @@ class LineLength(configRules: List<RulesConfig>) : DiktatRule(
             return LongLineFixableCases.None
         }
         // minus 2 here as we are inserting ` +` and we don't want it to exceed line length
-        val shouldAddTwoSpaces = multiLineOffset == 0 && leftOffset + delimiterIndex > configuration.lineLength.toInt() - 2
+        val shouldAddTwoSpaces = (multiLineOffset == 0) && (leftOffset + delimiterIndex > configuration.lineLength.toInt() - 2)
         val correcterDelimiter = if (shouldAddTwoSpaces) {
             node.text.substring(0, delimiterIndex - 2).lastIndexOf(' ')
         } else {
             delimiterIndex
         }
+        if (correcterDelimiter == -1) {
+            return LongLineFixableCases.None
+        }
         return LongLineFixableCases.StringTemplate(node, correcterDelimiter, multiLineOffset == 0)
     }
 
@@ -330,7 +334,7 @@ class LineLength(configRules: List<RulesConfig>) : DiktatRule(
         binList.forEachIndexed { index, astNode ->
             binaryText += findAllText(astNode)
             if (leftOffset + binaryText.length > wrongBinaryExpression.maximumLineLength && index != 0) {
-                val commonParent = astNode.parent({ it in binList[index - 1].parents() })!!
+                val commonParent = astNode.parent({ it.elementType == BINARY_EXPRESSION && it in binList[index - 1].parents() })!!
                 val nextNode = commonParent.findChildByType(OPERATION_REFERENCE)!!.treeNext
                 if (!nextNode.text.contains("\n")) {
                     commonParent.appendNewlineMergingWhiteSpace(nextNode, nextNode)
@@ -429,19 +433,33 @@ class LineLength(configRules: List<RulesConfig>) : DiktatRule(
         }
     }
 
+    /**
+     * Collect by Depth-first search (DFS) all children to the right side of the equal sign with specific type [propertyList],
+     * by which we can split expression.
+     * Such logic needed, because AST representation of complex conditions is quite loaded
+     *
+     * @param node target node to be processed
+     * @param binList where to store the corresponding results
+     */
     private fun dfsForProperty(node: ASTNode, binList: MutableList<ASTNode>) {
         node.getChildren(null).forEach {
             if (it.elementType in propertyList) {
-                if (it.elementType == REFERENCE_EXPRESSION && it.treeParent.elementType == CALL_EXPRESSION) {
-                    binList.add(it.treeParent)
+                if (it.elementType == REFERENCE_EXPRESSION && it.treeParent?.elementType == CALL_EXPRESSION) {
+                    binList.tryAdd(it.treeParent)
                 } else {
-                    binList.add(it)
+                    binList.tryAdd(it)
                 }
             }
             dfsForProperty(it, binList)
         }
     }
 
+    private fun MutableList<ASTNode>.tryAdd(node: ASTNode) {
+        if (node !in this) {
+            this.add(node)
+        }
+    }
+
     private fun createSplitProperty(wrongProperty: LongLineFixableCases.Property) {
         val node = wrongProperty.node
         val indexLastSpace = wrongProperty.indexLastSpace
@@ -479,7 +497,7 @@ class LineLength(configRules: List<RulesConfig>) : DiktatRule(
 
         /**
          * @property node node
-         * @property hasNewLineBefore flag to handle type of comment: ordinary comment(long part of which should be moved to the next line)
+         * @property hasNewLineBefore flag to handle type of comment: ordinary comment (long part of which should be moved to the next line)
          * and inline comments (which should be moved entirely to the previous line)
          * @property indexLastSpace index of last space to substring comment
          */
@@ -525,6 +543,6 @@ class LineLength(configRules: List<RulesConfig>) : DiktatRule(
         private const val STRING_PART_OFFSET = 4
         private val propertyList = listOf(INTEGER_CONSTANT, LITERAL_STRING_TEMPLATE_ENTRY, FLOAT_CONSTANT,
             CHARACTER_CONSTANT, REFERENCE_EXPRESSION, BOOLEAN_CONSTANT, LONG_STRING_TEMPLATE_ENTRY,
-            SHORT_STRING_TEMPLATE_ENTRY)
+            SHORT_STRING_TEMPLATE_ENTRY, NULL)
     }
 }

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

@@ -40,6 +40,11 @@ class LineLengthFixTest : FixTestBase("test/paragraph3/long_line", ::LineLength)
         fixAndCompare("LongLineExpressionExpected.kt", "LongLineExpressionTest.kt", rulesConfigListLineLength)
     }
 
+    @Test
+    fun `should fix complex long binary expressions`() {
+        fixAndCompare("LongBinaryExpressionExpected.kt", "LongBinaryExpressionTest.kt", rulesConfigListLineLength)
+    }
+
     @Test
     fun `should fix long function`() {
         fixAndCompare("LongLineFunExpected.kt", "LongLineFunTest.kt", rulesConfigListLineLength)

diktat-rules/src/test/resources/test/paragraph3/long_line/LongBinaryExpressionExpected.kt

@@ -0,0 +1,35 @@
+package test.paragraph3.long_line
+
+fun foo() {
+    val veryLongExpression = Methoooooooooooooooood() +
+ 12345
+
+    val veryLongExpression = Methoooooooooooooooood() ?:
+ null
+
+    val veryLongExpression = a.Methooooood() +
+ b.field
+
+    val variable = someField.filter { it.elementType == KDOC }
+
+    // limit at the left side
+    val variable = a?.filter { it.elementType == KDOC } ?:
+ null
+
+    // limit at the right side
+    val variable = bar?.filter { it.b == c } ?:
+ null
+
+    // limit at the operation reference
+    val variable = field?.filter { bar == foo } ?:
+ null
+
+    val variable = Methoooooooooooooooooooooooooood() ?:
+ "some loooooong string"
+
+    val variable = Methooooood() ?: "some" +
+" looong string"
+
+    var headerKdoc = firstCodeNode.prevSibling { it.elementType == KDOC } ?:
+ if (firstCodeNode == packageDirectiveNode) importsList?.prevSibling { it.elementType == KDOC } else null
+}

diktat-rules/src/test/resources/test/paragraph3/long_line/LongBinaryExpressionTest.kt

@@ -0,0 +1,26 @@
+package test.paragraph3.long_line
+
+fun foo() {
+    val veryLongExpression = Methoooooooooooooooood() + 12345
+
+    val veryLongExpression = Methoooooooooooooooood() ?: null
+
+    val veryLongExpression = a.Methooooood() + b.field
+
+    val variable = someField.filter { it.elementType == KDOC }
+
+    // limit at the left side
+    val variable = a?.filter { it.elementType == KDOC } ?: null
+
+    // limit at the right side
+    val variable = bar?.filter { it.b == c } ?: null
+
+    // limit at the operation reference
+    val variable = field?.filter { bar == foo } ?: null
+
+    val variable = Methoooooooooooooooooooooooooood() ?: "some loooooong string"
+
+    val variable = Methooooood() ?: "some looong string"
+
+    var headerKdoc = firstCodeNode.prevSibling { it.elementType == KDOC } ?: if (firstCodeNode == packageDirectiveNode) importsList?.prevSibling { it.elementType == KDOC } else null
+}

diktat-rules/src/test/resources/test/paragraph3/long_line/LongLineRValueExpected.kt

@@ -24,6 +24,8 @@ fun foo() {
     val longStringExpression = "First part" +
 "second Part"
 
+    val longStringExpression = "First" + "second Part"
+
     val longStringExpression = "First very long" +
 " part" + "second Part"
 

diktat-rules/src/test/resources/test/paragraph3/long_line/LongLineRValueTest.kt

@@ -19,6 +19,8 @@ fun foo() {
 
     val longStringExpression = "First part" + "second Part"
 
+    val longStringExpression = "First" + "second Part"
+
     val longStringExpression = "First very long part" + "second Part"
 
     val longStringExpression2 =                   "String starts at the line len limit"