Options for blank lines between 'when' branches

#KT-18607 Fixed

idea/formatter/src/org/jetbrains/kotlin/idea/core/formatter/KotlinCodeStyleSettings.java

@@ -43,6 +43,7 @@ public class KotlinCodeStyleSettings extends CustomCodeStyleSettings {
     public boolean CONTINUATION_INDENT_IN_PARAMETER_LISTS = true;
     public boolean CONTINUATION_INDENT_FOR_EXPRESSION_BODIES = true;
     public boolean CONTINUATION_INDENT_FOR_CHAINED_CALLS = true;
+    public int BLANK_LINES_AROUND_BLOCK_WHEN_BRANCHES = 0;
 
     public KotlinCodeStyleSettings(CodeStyleSettings container) {
         super("JetCodeStyleSettings", container);

idea/formatter/src/org/jetbrains/kotlin/idea/formatter/kotlinSpacingRules.kt

@@ -31,10 +31,7 @@ import org.jetbrains.kotlin.idea.core.formatter.KotlinCodeStyleSettings
 import org.jetbrains.kotlin.idea.formatter.KotlinSpacingBuilder.CustomSpacingBuilder
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.lexer.KtTokens.*
-import org.jetbrains.kotlin.psi.KtClass
+import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.psi.KtFunction
-import org.jetbrains.kotlin.psi.KtPrimaryConstructor
-import org.jetbrains.kotlin.psi.KtPropertyAccessor
 import org.jetbrains.kotlin.psi.psiUtil.textRangeWithoutComments
 
 val MODIFIERS_LIST_ENTRIES = TokenSet.orSet(TokenSet.create(ANNOTATION_ENTRY, ANNOTATION), MODIFIER_KEYWORDS)
@@ -256,8 +253,6 @@ fun createSpacingBuilder(settings: CodeStyleSettings, builderUtil: KotlinSpacing
             betweenInside(REFERENCE_EXPRESSION, LAMBDA_ARGUMENT, CALL_EXPRESSION).spaces(1)
             betweenInside(TYPE_ARGUMENT_LIST, LAMBDA_ARGUMENT, CALL_EXPRESSION).spaces(1)
 
-            between(WHEN_ENTRY, WHEN_ENTRY).lineBreakInCode()
-
             around(COLONCOLON).spaces(0)
 
             around(BY_KEYWORD).spaces(1)
@@ -373,6 +368,17 @@ fun createSpacingBuilder(settings: CodeStyleSettings, builderUtil: KotlinSpacing
 
             inPosition(right = CLASS_BODY).customRule(leftBraceRule(blockType = CLASS_BODY))
 
+            inPosition(left = WHEN_ENTRY, right = WHEN_ENTRY).customRule { _, left, right ->
+                val leftEntry = left.node.psi as KtWhenEntry
+                val rightEntry = right.node.psi as KtWhenEntry
+                val blankLines = if (leftEntry.expression is KtBlockExpression || rightEntry.expression is KtBlockExpression)
+                    settings.kotlinSettings.BLANK_LINES_AROUND_BLOCK_WHEN_BRANCHES
+                else
+                    0
+
+                createSpacing(0, minLineFeeds = blankLines + 1)
+            }
+
             inPosition(parent = WHEN_ENTRY, right = BLOCK).customRule(leftBraceRule())
             inPosition(parent = WHEN, right = LBRACE).customRule {
                 parent, _, _ ->

idea/src/org/jetbrains/kotlin/idea/formatter/KotlinLanguageCodeStyleSettingsProvider.kt

@@ -76,6 +76,24 @@ class KotlinLanguageCodeStyleSettingsProvider : LanguageCodeStyleSettingsProvide
 
                            field1
                        }
+
+                       when(field1) {
+                           1 -> println("1")
+                           2 -> println("2")
+                           3 ->
+                                println("3" +
+                                     "4")
+                       }
+
+                       when(field2) {
+                           1 -> {
+                               println("1")
+                           }
+
+                           2 -> {
+                               println("2")
+                           }
+                       }
                    }
 
 
@@ -231,10 +249,15 @@ class KotlinLanguageCodeStyleSettingsProvider : LanguageCodeStyleSettingsProvide
                                 "Put left brace on new line",
                                  CodeStyleSettingsCustomizable.WRAPPING_BRACES)
             }
-            LanguageCodeStyleSettingsProvider.SettingsType.BLANK_LINES_SETTINGS -> consumer.showStandardOptions(
+            LanguageCodeStyleSettingsProvider.SettingsType.BLANK_LINES_SETTINGS -> {
-                    "KEEP_BLANK_LINES_IN_CODE",
+                consumer.showStandardOptions(
-                    "KEEP_BLANK_LINES_IN_DECLARATIONS"
+                        "KEEP_BLANK_LINES_IN_CODE",
-            )
+                        "KEEP_BLANK_LINES_IN_DECLARATIONS"
+                )
+                showCustomOption(KotlinCodeStyleSettings::BLANK_LINES_AROUND_BLOCK_WHEN_BRANCHES,
+                                 "Around 'when' branches with {}",
+                                 CodeStyleSettingsCustomizable.BLANK_LINES)
+            }
             else -> consumer.showStandardOptions()
         }
     }

idea/testData/formatter/WhenBlockBlankLines.after.kt

@@ -0,0 +1,13 @@
+fun f(x: Int) = when (x) {
+    1 -> "Foo"
+    2 -> "Bar"
+
+    3 -> {
+        "Foo"
+    }
+
+    4 -> "Bar"
+    else -> "Xyzzy"
+}
+
+// SET_INT: BLANK_LINES_AROUND_BLOCK_WHEN_BRANCHES = 1

idea/testData/formatter/WhenBlockBlankLines.kt

@@ -0,0 +1,11 @@
+fun f(x: Int) = when(x) {
+    1 -> "Foo"
+    2 -> "Bar"
+    3 -> {
+        "Foo"
+    }
+    4 -> "Bar"
+    else -> "Xyzzy"
+}
+
+// SET_INT: BLANK_LINES_AROUND_BLOCK_WHEN_BRANCHES = 1

idea/tests/org/jetbrains/kotlin/formatter/FormatterTestGenerated.java

@@ -764,6 +764,12 @@ public class FormatterTestGenerated extends AbstractFormatterTest {
             doTest(fileName);
         }
 
+        @TestMetadata("WhenBlockBlankLines.after.kt")
+        public void testWhenBlockBlankLines() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/formatter/WhenBlockBlankLines.after.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("WhenEntryExpr.after.kt")
         public void testWhenEntryExpr() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/formatter/WhenEntryExpr.after.kt");