From 6adf8509afda865fea16366d80b2545ce2cef981 Mon Sep 17 00:00:00 2001
From: Aleksey Pivovarov <ampivovarov@gmail.com>
Date: Wed, 14 Dec 2016 12:48:12 +0300
Subject: [PATCH] merge: abort patch applying in read-only documents

---
 .../src/com/intellij/diff/tools/util/SimpleDiffPanel.java  | 6 +++++-
 .../openapi/vcs/changes/patch/tool/ApplyPatchViewer.java   | 7 ++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/platform/diff-impl/src/com/intellij/diff/tools/util/SimpleDiffPanel.java b/platform/diff-impl/src/com/intellij/diff/tools/util/SimpleDiffPanel.java
index d2be844f7e66..14316f037f57 100644
--- a/platform/diff-impl/src/com/intellij/diff/tools/util/SimpleDiffPanel.java
+++ b/platform/diff-impl/src/com/intellij/diff/tools/util/SimpleDiffPanel.java
@@ -35,7 +35,6 @@ public class SimpleDiffPanel extends DiffPanelBase {
     JPanel centerPanel = JBUI.Panels.simplePanel(editorPanel).addToTop(myNotificationsPanel);
 
     myContentPanel.add(centerPanel, GOOD_CONTENT);
-    myContentPanel.add(DiffUtil.createMessagePanel("Error"), ERROR_CONTENT);
 
     setCurrentCard(GOOD_CONTENT, false);
   }
@@ -49,6 +48,11 @@ public class SimpleDiffPanel extends DiffPanelBase {
   }
 
   public void setErrorContent() {
+    setErrorContent("Error");
+  }
+
+  public void setErrorContent(@NotNull String message) {
+    myContentPanel.add(DiffUtil.createMessagePanel(message), ERROR_CONTENT);
     setCurrentCard(ERROR_CONTENT);
   }
 
diff --git a/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/tool/ApplyPatchViewer.java b/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/tool/ApplyPatchViewer.java
index 45c04c14ccaf..d678ccec14ee 100644
--- a/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/tool/ApplyPatchViewer.java
+++ b/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/tool/ApplyPatchViewer.java
@@ -49,6 +49,7 @@ import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.BooleanGetter;
 import com.intellij.openapi.util.Disposer;
 import com.intellij.openapi.util.Pair;
+import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.openapi.vcs.changes.patch.AppliedTextPatch;
 import com.intellij.util.containers.ContainerUtil;
 import gnu.trove.TIntArrayList;
@@ -285,10 +286,14 @@ class ApplyPatchViewer implements DataProvider, Disposable {
 
   protected void initPatchViewer() {
     final Document outputDocument = myResultEditor.getDocument();
-    DiffUtil.executeWriteCommand(outputDocument, myProject, "Init merge content", () -> {
+    boolean success = DiffUtil.executeWriteCommand(outputDocument, myProject, "Init merge content", () -> {
       outputDocument.setText(myPatchRequest.getLocalContent());
       if (!isReadOnly()) DiffUtil.putNonundoableOperation(myProject, outputDocument);
     });
+    if (!success && !StringUtil.equals(outputDocument.getText(), myPatchRequest.getLocalContent())) {
+      myPanel.setErrorContent("Failed to display patch applier - local content was modified");
+      return;
+    }
 
 
     PatchChangeBuilder builder = new PatchChangeBuilder();