KT-5203 Do not offer to convert from java on paste if conversion is trivial

#KT-5203 Fixed

idea/src/org/jetbrains/kotlin/idea/conversion/copy/ConvertJavaCopyPastePostProcessor.kt

@@ -66,40 +66,54 @@ public class ConvertJavaCopyPastePostProcessor : CopyPastePostProcessor<TextBloc
         if (DumbService.getInstance(project).isDumb()) return
 
         val data = values.single()
-
         if (data !is CopiedCode) return
 
-        val sourceFile = PsiFileFactory.getInstance(project).
-                createFileFromText(data.fileName, JavaLanguage.INSTANCE, data.fileText) as? PsiJavaFile ?: return
-
         val targetFile = PsiDocumentManager.getInstance(project).getPsiFile(editor.getDocument()) as? JetFile ?: return
 
+        fun doConversion(): String? {
+            val sourceFile = PsiFileFactory.getInstance(project).
+                    createFileFromText(data.fileName, JavaLanguage.INSTANCE, data.fileText) as PsiJavaFile
+            return convertCopiedCodeToKotlin(data, sourceFile, targetFile)
+        }
+
+        var conversionResult: String? = null
+
+        val textLength = data.startOffsets.indices.sumBy { data.endOffsets[it] - data.startOffsets[it] }
+        if (textLength < 1000) { // if the text to convert is short enough, try to do conversion without permission from user and skip the dialog if nothing converted
+            conversionResult = doConversion() ?: return
+        }
+
         val jetEditorOptions = JetEditorOptions.getInstance()!!
         val needConvert = jetEditorOptions.isEnableJavaToKotlinConversion() && (jetEditorOptions.isDonTShowConversionDialog() || okFromDialog(project))
         if (needConvert) {
-            val text = convertCopiedCodeToKotlin(data, sourceFile, data.fileText, targetFile)
-            if (!text.isEmpty()) {
-                ApplicationManager.getApplication()!!.runWriteAction {
-                    val startOffset = bounds.getStartOffset()
-                    editor.getDocument().replaceString(startOffset, bounds.getEndOffset(), text)
+            if (conversionResult == null) {
+                conversionResult = doConversion() ?: return
+            }
+            ApplicationManager.getApplication()!!.runWriteAction {
+                val startOffset = bounds.getStartOffset()
+                editor.getDocument().replaceString(startOffset, bounds.getEndOffset(), conversionResult!!)
 
-                    val endOffsetAfterCopy = startOffset + text.length()
-                    editor.getCaretModel().moveToOffset(endOffsetAfterCopy)
+                val endOffsetAfterCopy = startOffset + conversionResult!!.length()
+                editor.getCaretModel().moveToOffset(endOffsetAfterCopy)
 
-                    CodeStyleManager.getInstance(project)!!.reformatText(targetFile, startOffset, endOffsetAfterCopy)
-                }
+                CodeStyleManager.getInstance(project)!!.reformatText(targetFile, startOffset, endOffsetAfterCopy)
+
+                conversionPerformed = true
             }
         }
     }
 
-    private fun convertCopiedCodeToKotlin(code: CopiedCode, sourceFile: PsiJavaFile, sourceFileText: String, targetFile: JetFile): String {
+    private fun convertCopiedCodeToKotlin(code: CopiedCode, sourceFile: PsiJavaFile, targetFile: JetFile): String? {
         assert(code.startOffsets.size() == code.endOffsets.size(), "Must have the same size")
+        val sourceFileText = code.fileText
 
         val list = ArrayList<Any>()
         for (i in code.startOffsets.indices) {
             list.collectElementsToConvert(sourceFile, sourceFileText, TextRange(code.startOffsets[i], code.endOffsets[i]))
         }
 
+        if (list.all { it is String }) return null // nothing to convert
+
         val converter = JavaToKotlinConverter(
                 sourceFile.getProject(),
                 ConverterSettings.defaultSettings,
@@ -110,24 +124,31 @@ public class ConvertJavaCopyPastePostProcessor : CopyPastePostProcessor<TextBloc
         val results = converter.elementsToKotlin(list.filterIsInstance<PsiElement>().map { it to J2kPostProcessor(targetFile, formatCode = false) })
 
         var resultIndex = 0
-        val text = StringBuilder {
-            for (o in list) {
-                if (o is PsiElement) {
-                    val result = results[resultIndex++]
-                    if (!result.isEmpty()) {
-                        append(result)
-                    }
-                    else { // failed to convert element to Kotlin, insert "as is"
-                        append(o.getText())
-                    }
+        val convertedCodeBuilder = StringBuilder()
+        val originalCodeBuilder = StringBuilder()
+        for (o in list) {
+            if (o is PsiElement) {
+                val originalText = o.getText()
+                val result = results[resultIndex++]
+                if (!result.isEmpty()) {
+                    convertedCodeBuilder.append(result)
                 }
-                else {
-                    append(o as String)
+                else { // failed to convert element to Kotlin, insert "as is"
+                    convertedCodeBuilder.append(originalText)
                 }
+                originalCodeBuilder.append(originalText)
             }
-        }.toString()
+            else {
+                convertedCodeBuilder.append(o as String)
+                originalCodeBuilder.append(o)
+            }
+        }
 
-        return StringUtil.convertLineSeparators(text)
+        val convertedCode = convertedCodeBuilder.toString()
+        val originalCode = originalCodeBuilder.toString()
+        if (convertedCode == originalCode) return null
+
+        return convertedCode
     }
 
     // builds list consisting of PsiElement's to convert and plain String's
@@ -178,4 +199,9 @@ public class ConvertJavaCopyPastePostProcessor : CopyPastePostProcessor<TextBloc
         dialog.show()
         return dialog.isOK()
     }
+
+    companion object {
+        // used for testing
+        public var conversionPerformed: Boolean = false
+    }
 }

idea/testData/copyPaste/conversion/Arithmetic.expected.kt

@@ -1 +1 @@
-b - c + d
+No conversion performed

idea/testData/copyPaste/conversion/Arithmetic.to.kt

@@ -1 +1 @@
-<caret>
+val v = <caret>

idea/testData/copyPaste/conversion/MethodReferenceWithoutQualifier.expected.kt

@@ -1,4 +1 @@
-fun main(args: Array<String>) {
-    reference(arg)
-    somethingElse()
-}
+No conversion performed

idea/testData/copyPaste/conversion/OnlyClosingBrace.expected.kt

@@ -1 +1 @@
-}
+No conversion performed

idea/testData/copyPaste/conversion/OnlyQualifier.expected.kt

@@ -1,4 +1 @@
-fun main(args: Array<String>) {
-    qualifier
-    somethingElse()
-}
+No conversion performed

idea/testData/copyPaste/conversion/SingleWordFromIdentifier.expected.kt

@@ -1 +1 @@
-class Some
+No conversion performed

idea/tests/org/jetbrains/kotlin/idea/conversion/copy/AbstractJavaToKotlinCopyPasteConversionTest.java

@@ -17,8 +17,10 @@
 package org.jetbrains.kotlin.idea.conversion.copy;
 
 import com.intellij.openapi.actionSystem.IdeActions;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.command.CommandProcessor;
+import com.intellij.openapi.editor.Document;
 import com.intellij.testFramework.LightProjectDescriptor;
-import com.intellij.testFramework.fixtures.LightCodeInsightFixtureTestCase;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.idea.JetLightCodeInsightFixtureTestCase;
 import org.jetbrains.kotlin.idea.JetWithJdkAndRuntimeLightProjectDescriptor;
@@ -55,8 +57,28 @@ public abstract class AbstractJavaToKotlinCopyPasteConversionTest extends JetLig
         String testName = getTestName(false);
         myFixture.configureByFile(testName + ".java");
         myFixture.performEditorAction(IdeActions.ACTION_COPY);
+
+        //noinspection AssignmentToStaticFieldFromInstanceMethod
+        ConvertJavaCopyPastePostProcessor.conversionPerformed = false;
+
         myFixture.configureByFile(testName + ".to.kt");
         myFixture.performEditorAction(IdeActions.ACTION_PASTE);
+
+        if (!ConvertJavaCopyPastePostProcessor.conversionPerformed) {
+            CommandProcessor.getInstance().executeCommand(getProject(), new Runnable() {
+                @Override
+                public void run() {
+                    ApplicationManager.getApplication().runWriteAction(new Runnable() {
+                        @Override
+                        public void run() {
+                            Document document = myFixture.getEditor().getDocument();
+                            document.replaceString(0, document.getTextLength(), "No conversion performed");
+                        }
+                    });
+                }
+            }, "", null);
+        }
+
         myFixture.checkResultByFile(testName + ".expected.kt");
     }
 }