Folding: add replacing with inferred type for var as folding: IDEA-194935

java/java-impl/src/com/intellij/application/options/editor/JavaCodeFoldingOptionsProvider.java

@@ -39,6 +39,8 @@ public class JavaCodeFoldingOptionsProvider extends BeanConfigurable<JavaCodeFol
 
     checkBox(ApplicationBundle.message("checkbox.collapse.generic.constructor.parameters"), settings::isCollapseConstructorGenericParameters, settings::setCollapseConstructorGenericParameters);
 
+    checkBox(ApplicationBundle.message("checkbox.collapse.inferred.type"), settings::isReplaceVarWithInferredType, settings::setReplaceVarWithInferredType);
+
     checkBox(ApplicationBundle.message("checkbox.collapse.i18n.messages"), settings::isCollapseI18nMessages, settings::setCollapseI18nMessages);
 
     checkBox(ApplicationBundle.message("checkbox.collapse.suppress.warnings"), settings::isCollapseSuppressWarnings, settings::setCollapseSuppressWarnings);

java/java-psi-api/src/com/intellij/codeInsight/folding/JavaCodeFoldingSettings.java

@@ -65,4 +65,7 @@ public abstract class JavaCodeFoldingSettings {
 
   public abstract boolean isCollapseEndOfLineComments();
   public abstract void setCollapseEndOfLineComments(boolean value);
+
+  public abstract boolean isReplaceVarWithInferredType();
+  public abstract void setReplaceVarWithInferredType(boolean value);
 }

java/java-psi-impl/src/com/intellij/codeInsight/folding/impl/JavaCodeFoldingSettingsBase.java

@@ -29,6 +29,7 @@ public class JavaCodeFoldingSettingsBase extends JavaCodeFoldingSettings {
   private boolean COLLAPSE_I18N_MESSAGES = true;
   private boolean COLLAPSE_SUPPRESS_WARNINGS = true;
   private boolean COLLAPSE_END_OF_LINE_COMMENTS;
+  private boolean REPLACE_VAR_WITH_INFERRED_TYPE = false;
 
   @Override
   public boolean isCollapseImports() {
@@ -168,4 +169,14 @@ public class JavaCodeFoldingSettingsBase extends JavaCodeFoldingSettings {
   public void setCollapseEndOfLineComments(boolean value) {
     COLLAPSE_END_OF_LINE_COMMENTS = value;
   }
+
+  @Override
+  public boolean isReplaceVarWithInferredType() {
+    return REPLACE_VAR_WITH_INFERRED_TYPE;
+  }
+
+  @Override
+  public void setReplaceVarWithInferredType(boolean value) {
+    REPLACE_VAR_WITH_INFERRED_TYPE = value;
+  }
 }

java/java-psi-impl/src/com/intellij/codeInsight/folding/impl/JavaFoldingBuilderBase.java

@@ -269,6 +269,17 @@ public abstract class JavaFoldingBuilderBase extends CustomFoldingBuilder implem
     addTypeParametersFolding(list, document, parameterList, 3, quick);
   }
 
+  private static void addLocalVariableTypeFolding(@NotNull List<? super FoldingDescriptor> list,
+                                                  @NotNull PsiVariable expression,
+                                                  boolean quick) {
+    if (quick) return; // presentable text may require resolve
+    PsiTypeElement typeElement = expression.getTypeElement();
+    if (typeElement == null) return;
+    if (!typeElement.isInferredType()) return;
+    String presentableText = expression.getType().getPresentableText();
+    list.add(new NamedFoldingDescriptor(typeElement.getNode(), typeElement.getTextRange(), null, presentableText, true, Collections.emptySet()));
+  }
+
   private static boolean resolvesCorrectly(@NotNull PsiReferenceExpression expression) {
     for (final JavaResolveResult result : expression.multiResolve(true)) {
   if (!result.isValidResult()) {
@@ -550,7 +561,7 @@ public abstract class JavaFoldingBuilderBase extends CustomFoldingBuilder implem
     }
 
     PsiCodeBlock body = method.getBody();
-    if (body != null && !oneLiner) {
+    if (body != null) {
       addCodeBlockFolds(list, body, processedComments, document, quick);
     }
   }
@@ -678,6 +689,15 @@ public abstract class JavaFoldingBuilderBase extends CustomFoldingBuilder implem
         }
       }
 
+      @Override
+      public void visitLocalVariable(PsiLocalVariable variable) {
+        if (!dumb && JavaCodeFoldingSettings.getInstance().isReplaceVarWithInferredType()) {
+          addLocalVariableTypeFolding(list, variable, quick);
+        }
+
+        super.visitLocalVariable(variable);
+      }
+
       @Override
       public void visitMethodCallExpression(PsiMethodCallExpression expression) {
         if (!dumb) {

java/java-tests/testSrc/com/intellij/java/codeInsight/folding/JavaFolding10Test.kt

@@ -0,0 +1,25 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.java.codeInsight.folding
+
+import com.intellij.testFramework.LightProjectDescriptor
+import org.assertj.core.api.Assertions.assertThat
+
+class JavaFolding10Test : JavaFoldingTestCase() {
+  override fun getProjectDescriptor(): LightProjectDescriptor = JAVA_10
+
+  fun testLocalVariable() {
+    val text = """
+        class A {
+          void test() {
+            var x = "FOO";
+          }
+        }""".trimIndent()
+    configure(text)
+
+    val regions = myFixture.editor.foldingModel.allFoldRegions
+    assertThat(regions).hasSize(3)
+
+    val region = regions[1]
+    assertThat(region.placeholderText).isEqualTo("String")
+  }
+}

platform/platform-resources-en/src/messages/ApplicationBundle.properties

@@ -398,6 +398,7 @@ checkbox.collapse.data.uri=Data URIs
 checkbox.collapse.anonymous.classes=<html>Anonymous classes</html>
 checkbox.collapse.closures=<html>"Closures" (anonymous classes implementing one method, before Java 8)</html>
 checkbox.collapse.generic.constructor.parameters=<html>Generic constructor and method parameters</html>
+checkbox.collapse.inferred.type=<html>Replace 'var' with inferred type</html>
 checkbox.collapse.i18n.messages=<html>I18n strings</html>
 checkbox.collapse.annotations=<html>Annotations</html>
 checkbox.collapse.inner.classes=Inner classes