"Join lines" works incorrectly in case of line with more than one string literal (KT-22374)

#KT-22374 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToStringTemplateIntention.kt

@@ -57,7 +57,7 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
         }
 
         @JvmStatic
-        fun buildReplacement(expression: KtBinaryExpression): KtStringTemplateExpression {
+        protected fun buildReplacement(expression: KtBinaryExpression): KtStringTemplateExpression {
             val rightText = buildText(expression.right, false)
             return fold(expression.left, rightText, KtPsiFactory(expression))
         }
@@ -75,7 +75,7 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
             }
         }
 
-        private fun buildText(expr: KtExpression?, forceBraces: Boolean): String {
+        fun buildText(expr: KtExpression?, forceBraces: Boolean): String {
             if (expr == null) return ""
             val expression = KtPsiUtil.safeDeparenthesize(expr)
             val expressionText = expression.text
@@ -130,7 +130,7 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
             return "\${$expressionText}"
         }
 
-        fun isApplicableToNoParentCheck(expression: KtBinaryExpression): Boolean {
+        private fun isApplicableToNoParentCheck(expression: KtBinaryExpression): Boolean {
             if (expression.operationToken != KtTokens.PLUS) return false
             val expressionType = expression.analyze(BodyResolveMode.PARTIAL).getType(expression)
             if (!KotlinBuiltIns.isString(expressionType)) return false

idea/src/org/jetbrains/kotlin/idea/joinLines/JoinToStringTemplateHandler.kt

@@ -20,10 +20,10 @@ import com.intellij.codeInsight.editorActions.JoinRawLinesHandlerDelegate
 import com.intellij.openapi.editor.Document
 import com.intellij.psi.PsiFile
 import org.jetbrains.kotlin.idea.intentions.ConvertToStringTemplateIntention
+import org.jetbrains.kotlin.idea.intentions.branchedTransformations.lineCount
+import org.jetbrains.kotlin.idea.refactoring.getLineCount
 import org.jetbrains.kotlin.lexer.KtTokens
-import org.jetbrains.kotlin.psi.KtBinaryExpression
-import org.jetbrains.kotlin.psi.KtFile
-import org.jetbrains.kotlin.psi.KtStringTemplateExpression
+import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
 
 class JoinToStringTemplateHandler : JoinRawLinesHandlerDelegate {
@@ -35,16 +35,61 @@ class JoinToStringTemplateHandler : JoinRawLinesHandlerDelegate {
         val index = if (c == '\n') start - 1 else start
 
         val plus = file.findElementAt(index)?.takeIf { it.node?.elementType == KtTokens.PLUS } ?: return -1
-        val expression = (plus.parent.parent as? KtBinaryExpression) ?: return -1
-        val left = expression.left ?: return -1
-        val right = expression.right ?: return -1
-        if (left !is KtStringTemplateExpression || right !is KtStringTemplateExpression) return -1
-        if (!ConvertToStringTemplateIntention.isApplicableToNoParentCheck(expression)) return -1
+        var binaryExpr = (plus.parent.parent as? KtBinaryExpression) ?: return -1
+        if (!binaryExpr.joinable()) return -1
 
-        val offset = left.endOffset - 1
-        expression.replace(ConvertToStringTemplateIntention.buildReplacement(expression))
-        return offset
+        val lineCount = binaryExpr.getLineCount()
+        val nextLineCount = lineCount + 1
+
+        var parent = binaryExpr.parent
+        while (parent is KtBinaryExpression && parent.joinable() && parent.lineCount() == nextLineCount) {
+            binaryExpr = parent
+            parent = parent.parent
+        }
+
+        var rightText = ConvertToStringTemplateIntention.buildText(binaryExpr.right, false)
+        var left = binaryExpr.left
+        while (left is KtBinaryExpression && left.joinable() && left.parent.getLineCount() >= lineCount) {
+            rightText = ConvertToStringTemplateIntention.buildText(left.right, false) + rightText
+            left = left.left
+        }
+
+        return when (left) {
+            is KtStringTemplateExpression -> {
+                val offset = left.endOffset - 1
+                binaryExpr.replace(createStringTemplate(left, rightText))
+                offset
+            }
+            is KtBinaryExpression -> {
+                val leftRight = left.right
+                if (leftRight is KtStringTemplateExpression) {
+                    val offset = leftRight.endOffset - 1
+                    leftRight.replace(createStringTemplate(leftRight, rightText))
+                    binaryExpr.replace(left)
+                    offset
+                } else {
+                    -1
+                }
+            }
+            else -> -1
+        }
+    }
+
+    private fun createStringTemplate(left: KtStringTemplateExpression, rightText: String): KtStringTemplateExpression {
+        val leftText = ConvertToStringTemplateIntention.buildText(left, false)
+        return KtPsiFactory(left).createExpression("\"$leftText$rightText\"") as KtStringTemplateExpression
     }
 
     override fun tryJoinLines(document: Document, file: PsiFile, start: Int, end: Int): Int = -1
-}
+}
+
+private fun KtBinaryExpression.joinable(): Boolean {
+    if (operationToken != KtTokens.PLUS) return false
+    if (right !is KtStringTemplateExpression) return false
+    val left = left
+    return when (left) {
+        is KtStringTemplateExpression -> true
+        is KtBinaryExpression -> left.right is KtStringTemplateExpression
+        else -> false
+    }
+}

idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteral.kt

@@ -0,0 +1,4 @@
+val s = "1" + "2" +
+        "3" + "4" +<caret>
+        "5" + "6" +
+        "7" + "8"

idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteral.kt.after

@@ -0,0 +1,3 @@
+val s = "1" + "2" +
+        "3<caret>456" +
+        "7" + "8"

idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteralAndVariable.kt

@@ -0,0 +1,5 @@
+val foo = "test"
+val s = "1" + "2" +
+        foo + "4" +<caret>
+        "5" + foo +
+        "7" + "8"

idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteralAndVariable.kt.after

@@ -0,0 +1,4 @@
+val foo = "test"
+val s = "1" + "2" +
+        foo + "4<caret>5" + foo +
+        "7" + "8"

idea/tests/org/jetbrains/kotlin/idea/intentions/declarations/JoinLinesTestGenerated.java

@@ -429,6 +429,18 @@ public class JoinLinesTestGenerated extends AbstractJoinLinesTest {
             doTest(fileName);
         }
 
+        @TestMetadata("lineWithMultiStringLiteral.kt")
+        public void testLineWithMultiStringLiteral() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteral.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("lineWithMultiStringLiteralAndVariable.kt")
+        public void testLineWithMultiStringLiteralAndVariable() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/stringTemplate/lineWithMultiStringLiteralAndVariable.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("secondLineVariable.kt")
         public void testSecondLineVariable() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/stringTemplate/secondLineVariable.kt");