diff: support code navigation and advanced highlighting for non-local files

* disable inspections and intentions for non-local files
-- Intentions should not be available for read-only content
-- Inspections generate lots of false-positive warnings (ex: unused statement).
   Disable them until we can run only known-to-be-correct ones.

java/java-impl/src/com/intellij/codeInsight/daemon/JavaProblemHighlightFilter.java

@@ -16,7 +16,7 @@
 package com.intellij.codeInsight.daemon;
 
 import com.intellij.ide.highlighter.JavaFileType;
-import com.intellij.ide.scratch.ScratchFileType;
+import com.intellij.openapi.fileTypes.PeripheralFileType;
 import com.intellij.openapi.roots.JavaProjectRootsUtil;
 import com.intellij.openapi.roots.ProjectFileIndex;
 import com.intellij.openapi.roots.ProjectRootManager;
@@ -28,7 +28,9 @@ import org.jetbrains.annotations.NotNull;
 public class JavaProblemHighlightFilter extends ProblemHighlightFilter {
   @Override
   public boolean shouldHighlight(@NotNull PsiFile psiFile) {
-    return psiFile.getFileType() != JavaFileType.INSTANCE || !JavaProjectRootsUtil.isOutsideJavaSourceRoot(psiFile) || (psiFile.getViewProvider().getFileType() ==  ScratchFileType.INSTANCE);
+    return psiFile.getFileType() != JavaFileType.INSTANCE ||
+           !JavaProjectRootsUtil.isOutsideJavaSourceRoot(psiFile) ||
+           psiFile.getViewProvider().getFileType() instanceof PeripheralFileType;
   }
 
   @Override

platform/core-api/src/com/intellij/openapi/fileTypes/PeripheralFileType.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.openapi.fileTypes;
+
+/**
+ * Marker interface for files that should be highlighted in a project context, despite of them not being part of it.
+ * Example: content from VCS, scratch files
+ *
+ * This file cannot be referenced from the rest of a project and might depend on no longer existent files.
+ * But we still can use project context to provide highlighting and code navigation in assumption, that local references are valid
+ * and non-local references still point at the right location.
+ */
+public interface PeripheralFileType extends FileType {
+}

platform/diff-impl/diff-impl.iml

@@ -13,5 +13,6 @@
     <orderEntry type="module" module-name="platform-impl" />
     <orderEntry type="module" module-name="vcs-api-core" />
     <orderEntry type="module" module-name="vcs-api" />
+    <orderEntry type="module" module-name="lang-api" />
   </component>
 </module>

platform/diff-impl/src/com/intellij/diff/contents/DiffPsiFileType.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.diff.contents;
+
+import com.intellij.codeInsight.daemon.impl.HighlightInfo;
+import com.intellij.codeInsight.daemon.impl.HighlightInfoFilter;
+import com.intellij.codeInsight.daemon.impl.IntentionActionFilter;
+import com.intellij.codeInsight.daemon.impl.analysis.DefaultHighlightingSettingProvider;
+import com.intellij.codeInsight.daemon.impl.analysis.FileHighlightingSetting;
+import com.intellij.codeInsight.intention.IntentionAction;
+import com.intellij.icons.AllIcons;
+import com.intellij.lang.Language;
+import com.intellij.lang.annotation.HighlightSeverity;
+import com.intellij.openapi.fileTypes.*;
+import com.intellij.openapi.fileTypes.ex.FileTypeIdentifiableByVirtualFile;
+import com.intellij.openapi.project.Project;
+import com.intellij.openapi.util.Key;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.LanguageSubstitutor;
+import com.intellij.psi.PsiFile;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.swing.*;
+
+public class DiffPsiFileType extends LanguageFileType implements FileTypeIdentifiableByVirtualFile, PeripheralFileType {
+  public static final Key<FileType> ORIGINAL_FILE_TYPE_KEY = Key.create("Diff.DiffPsiFileType.OriginalFileTypeKey");
+  public static final LanguageFileType INSTANCE = new DiffPsiFileType();
+
+  DiffPsiFileType() {
+    super(PlainTextLanguage.INSTANCE);
+  }
+
+  @Override
+  public boolean isMyFileType(@NotNull VirtualFile file) {
+    return isDiffFile(file);
+  }
+
+  @NotNull
+  @Override
+  public String getName() {
+    return "Diff";
+  }
+
+  @NotNull
+  @Override
+  public String getDescription() {
+    return "Diff";
+  }
+
+  @NotNull
+  @Override
+  public String getDefaultExtension() {
+    return "";
+  }
+
+  @Nullable
+  @Override
+  public Icon getIcon() {
+    return AllIcons.Diff.Diff;
+  }
+
+  @Override
+  public boolean isReadOnly() {
+    return true;
+  }
+
+  @Nullable
+  @Override
+  public String getCharset(@NotNull VirtualFile file, @NotNull byte[] content) {
+    return null;
+  }
+
+
+  public static class TypeFactory extends FileTypeFactory {
+    @Override
+    public void createFileTypes(@NotNull FileTypeConsumer consumer) {
+      consumer.consume(INSTANCE);
+    }
+  }
+
+  public static class Substitutor extends LanguageSubstitutor {
+    @Nullable
+    @Override
+    public Language getLanguage(@NotNull VirtualFile file, @NotNull Project project) {
+      FileType originalType = getOriginalFileType(file);
+      if (originalType instanceof LanguageFileType) {
+        return ((LanguageFileType)originalType).getLanguage();
+      }
+      return null;
+    }
+  }
+
+  public static class HighlightFilter implements HighlightInfoFilter {
+    @Override
+    public boolean accept(@NotNull HighlightInfo info, @Nullable PsiFile file) {
+      if (!isDiffFile(file)) return true;
+      if (info.getSeverity() == HighlightSeverity.ERROR) return false;
+      return true;
+    }
+  }
+
+  public static class IntentionFilter implements IntentionActionFilter {
+    @Override
+    public boolean accept(@NotNull IntentionAction intentionAction, @Nullable PsiFile file) {
+      return !isDiffFile(file);
+    }
+  }
+
+  public static class HighlightingSettingProvider extends DefaultHighlightingSettingProvider {
+    @Nullable
+    @Override
+    public FileHighlightingSetting getDefaultSetting(@NotNull Project project, @NotNull VirtualFile file) {
+      if (!isDiffFile(file)) return null;
+      return FileHighlightingSetting.SKIP_INSPECTION;
+    }
+  }
+
+
+  private static boolean isDiffFile(@Nullable PsiFile file) {
+    return file != null && isDiffFile(file.getVirtualFile());
+  }
+
+  private static boolean isDiffFile(@Nullable VirtualFile file) {
+    return file != null && getOriginalFileType(file) != null;
+  }
+
+  @Nullable
+  private static FileType getOriginalFileType(@NotNull VirtualFile file) {
+    FileType fileType = file.getUserData(ORIGINAL_FILE_TYPE_KEY);
+    return fileType instanceof DiffPsiFileType ? null : fileType;
+  }
+}

platform/diff-impl/src/com/intellij/diff/contents/FileAwareDocumentContent.java

@@ -4,6 +4,7 @@ import com.intellij.diff.tools.util.DiffNotifications;
 import com.intellij.diff.util.DiffUserDataKeysEx;
 import com.intellij.diff.util.DiffUtil;
 import com.intellij.diff.util.LineCol;
+import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.EditorFactory;
 import com.intellij.openapi.fileEditor.FileDocumentManager;
@@ -12,11 +13,14 @@ import com.intellij.openapi.fileTypes.FileType;
 import com.intellij.openapi.fileTypes.FileTypes;
 import com.intellij.openapi.fileTypes.PlainTextFileType;
 import com.intellij.openapi.project.Project;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.openapi.vcs.FilePath;
 import com.intellij.openapi.vfs.CharsetToolkit;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.pom.Navigatable;
+import com.intellij.psi.PsiDocumentManager;
+import com.intellij.testFramework.LightVirtualFile;
 import com.intellij.ui.LightColors;
 import com.intellij.util.LineSeparator;
 import com.intellij.util.diff.Diff;
@@ -107,7 +111,27 @@ public class FileAwareDocumentContent extends DocumentContentImpl {
     @NotNull
     private Builder create(@NotNull String content) {
       mySeparator = StringUtil.detectSeparators(content);
-      myDocument = EditorFactory.getInstance().createDocument(StringUtil.convertLineSeparators(content));
+      String correctedContent = StringUtil.convertLineSeparators(content);
+
+      if (myProject != null && Registry.is("diff.enable.psi.highlighting")) {
+        ApplicationManager.getApplication().runReadAction(() -> {
+          LightVirtualFile file = new LightVirtualFile(myFileName, DiffPsiFileType.INSTANCE, correctedContent);
+          file.setWritable(false);
+
+          file.putUserData(DiffPsiFileType.ORIGINAL_FILE_TYPE_KEY, myFileType);
+
+          myDocument = FileDocumentManager.getInstance().getDocument(file);
+          if (myDocument == null) {
+            myDocument = EditorFactory.getInstance().createDocument(correctedContent);
+          }
+
+          PsiDocumentManager.getInstance(myProject).getPsiFile(myDocument);
+        });
+      }
+      else {
+        myDocument = EditorFactory.getInstance().createDocument(correctedContent);
+      }
+
       myDocument.setReadOnly(true);
       return this;
     }

platform/diff-impl/src/com/intellij/diff/tools/util/side/TwosideTextDiffViewer.java

@@ -36,6 +36,7 @@ import com.intellij.diff.util.LineCol;
 import com.intellij.diff.util.Side;
 import com.intellij.openapi.actionSystem.AnAction;
 import com.intellij.openapi.actionSystem.AnActionEvent;
+import com.intellij.openapi.actionSystem.CommonDataKeys;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.ScrollType;
@@ -43,6 +44,9 @@ import com.intellij.openapi.editor.event.DocumentEvent;
 import com.intellij.openapi.editor.event.VisibleAreaEvent;
 import com.intellij.openapi.editor.event.VisibleAreaListener;
 import com.intellij.openapi.editor.ex.EditorEx;
+import com.intellij.openapi.fileEditor.FileEditorManager;
+import com.intellij.openapi.fileEditor.OpenFileDescriptor;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.pom.Navigatable;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.CalledInAwt;
@@ -350,8 +354,23 @@ public abstract class TwosideTextDiffViewer extends TwosideDiffViewer<TextEditor
   @Nullable
   @Override
   public Object getData(@NonNls String dataId) {
+    EditorEx editor = getCurrentEditor();
+    if (myProject != null && !myProject.isDisposed() && Registry.is("diff.enable.psi.highlighting")) {
+      final Object o = FileEditorManager.getInstance(myProject).getData(dataId, editor, editor.getCaretModel().getCurrentCaret());
+      if (o != null) return o;
+    }
+
     if (DiffDataKeys.CURRENT_EDITOR.is(dataId)) {
-      return getCurrentEditor();
+      return editor;
+    }
+    else if (CommonDataKeys.EDITOR.is(dataId)) {
+      return editor;
+    }
+    else if (CommonDataKeys.VIRTUAL_FILE.is(dataId)) {
+      return editor.getVirtualFile();
+    }
+    else if (OpenFileDescriptor.NAVIGATE_IN_EDITOR.is(dataId)) {
+      return editor;
     }
     return super.getData(dataId);
   }

platform/diff-impl/src/com/intellij/diff/util/DiffUtil.java

@@ -224,7 +224,11 @@ public class DiffUtil {
   public static void configureEditor(@NotNull EditorEx editor, @NotNull DocumentContent content, @Nullable Project project) {
     setEditorHighlighter(project, editor, content);
     setEditorCodeStyle(project, editor, content.getContentType());
-    editor.reinitSettings();
+
+    VirtualFile virtualFile = FileDocumentManager.getInstance().getFile(content.getDocument());
+    if (virtualFile != null && Registry.is("diff.enable.psi.highlighting")) {
+      editor.setFile(virtualFile);
+    }
   }
 
   public static boolean isMirrored(@NotNull Editor editor) {

platform/lang-impl/src/com/intellij/ide/scratch/ScratchFileType.java

@@ -16,6 +16,7 @@
 package com.intellij.ide.scratch;
 
 import com.intellij.openapi.fileTypes.LanguageFileType;
+import com.intellij.openapi.fileTypes.PeripheralFileType;
 import com.intellij.openapi.fileTypes.PlainTextFileType;
 import com.intellij.openapi.fileTypes.PlainTextLanguage;
 import com.intellij.openapi.fileTypes.ex.FileTypeIdentifiableByVirtualFile;
@@ -28,7 +29,7 @@ import javax.swing.*;
 /**
  * @author gregsh
  */
-public class ScratchFileType extends LanguageFileType implements FileTypeIdentifiableByVirtualFile {
+public class ScratchFileType extends LanguageFileType implements FileTypeIdentifiableByVirtualFile, PeripheralFileType {
 
   public static final LanguageFileType INSTANCE = new ScratchFileType();
 

platform/platform-resources/src/META-INF/PlatformExtensions.xml

@@ -107,6 +107,13 @@
     <colorAndFontPanelFactory implementation="com.intellij.openapi.diff.impl.settings.DiffColorsPageFactory"/>
     <colorAndFontDescriptorProvider implementation="com.intellij.openapi.diff.impl.settings.DiffColorsPageFactory"/>
 
+    <fileTypeFactory implementation="com.intellij.diff.contents.DiffPsiFileType$TypeFactory"/>
+    <lang.substitutor language="TEXT" implementationClass="com.intellij.diff.contents.DiffPsiFileType$Substitutor" order="first"/>
+    <daemon.highlightInfoFilter implementation="com.intellij.diff.contents.DiffPsiFileType$HighlightFilter"/>
+    <daemon.intentionActionFilter implementation="com.intellij.diff.contents.DiffPsiFileType$IntentionFilter"/>
+    <defaultHighlightingSettingProvider id="GeneratedSourcesHighlightingSettingProvider"
+                                        implementation="com.intellij.diff.contents.DiffPsiFileType$HighlightingSettingProvider"/>
+
     <applicationService serviceInterface="com.intellij.ui.SystemNotifications"
                         serviceImplementation="com.intellij.ui.SystemNotificationsImpl"/>
     <applicationService serviceInterface="com.intellij.openapi.keymap.KeymapGroupFactory"

platform/util/resources/misc/registry.properties

@@ -491,6 +491,8 @@ diff.divider.repainting.disable.blitting=true
 diff.divider.repainting.disable.blitting.description=Fix painting glitch on scrolling in diff - disable BLIT_SCROLL_MODE to force repainting with RepaintManager
 diff.merge.resolve.conflict.action.visible=false
 diff.merge.resolve.conflict.action.visible.description=Allows to resolve some conflict in merge in one click (with a high probability of wrong result)
+diff.enable.psi.highlighting=true
+diff.enable.psi.highlighting.description=Enable advanced highlighting and code navigation in VCS content in diff viewers.
 
 search.everywhere.toolwindows=true
 search.everywhere.files=true