From d1cf540decc930d49d5e63c39aad35bd35cad92c Mon Sep 17 00:00:00 2001
From: Kirill Likhodedov <Kirill.Likhodedov@jetbrains.com>
Date: Fri, 18 May 2018 23:02:49 +0300
Subject: [PATCH] vcs: fix atomicity of getting patched revision content

volatile wasn't protecting from multiple getContent() invocations.
---
 .../patch/LazyPatchContentRevision.java       | 58 ++++++++++++-------
 1 file changed, 37 insertions(+), 21 deletions(-)

diff --git a/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/LazyPatchContentRevision.java b/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/LazyPatchContentRevision.java
index b8c302ee9b5e..904ff6048c90 100644
--- a/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/LazyPatchContentRevision.java
+++ b/platform/vcs-impl/src/com/intellij/openapi/vcs/changes/patch/LazyPatchContentRevision.java
@@ -20,50 +20,56 @@ import com.intellij.openapi.diff.impl.patch.TextFilePatch;
 import com.intellij.openapi.diff.impl.patch.apply.GenericPatchApplier;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.fileEditor.FileDocumentManager;
+import com.intellij.openapi.util.AtomicNotNullLazyValue;
 import com.intellij.openapi.vcs.FilePath;
 import com.intellij.openapi.vcs.changes.ContentRevision;
 import com.intellij.openapi.vcs.history.VcsRevisionNumber;
 import com.intellij.openapi.vfs.VirtualFile;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 public class LazyPatchContentRevision implements ContentRevision {
-  private volatile String myContent;
   private final VirtualFile myVf;
   private final FilePath myNewFilePath;
   private final String myRevision;
   private final TextFilePatch myPatch;
-  private volatile boolean myPatchApplyFailed;
+
+  private final AtomicNotNullLazyValue<Data> myData;
 
   public LazyPatchContentRevision(final VirtualFile vf, final FilePath newFilePath, final String revision, final TextFilePatch patch) {
     myVf = vf;
     myNewFilePath = newFilePath;
     myRevision = revision;
     myPatch = patch;
+
+    myData = AtomicNotNullLazyValue.createValue(() -> loadContent());
   }
 
-  public String getContent() {
-    if (myContent == null) {
-      final String localContext = ReadAction.compute(() -> {
-        final Document doc = FileDocumentManager.getInstance().getDocument(myVf);
-        return doc == null ? null : doc.getText();
-      });
-      if (localContext == null) {
-        myPatchApplyFailed = true;
-        return null;
-      }
-
-      GenericPatchApplier.AppliedPatch appliedPatch = GenericPatchApplier.apply(localContext, myPatch.getHunks());
-      if (appliedPatch != null) {
-        myContent = appliedPatch.patchedText;
-      } else {
-        myPatchApplyFailed = true;
-      }
+  private Data loadContent() {
+    String localContext = ReadAction.compute(() -> {
+      Document doc = FileDocumentManager.getInstance().getDocument(myVf);
+      return doc == null ? null : doc.getText();
+    });
+    if (localContext == null) {
+      return new Data(null, true);
     }
-    return myContent;
+
+    GenericPatchApplier.AppliedPatch appliedPatch = GenericPatchApplier.apply(localContext, myPatch.getHunks());
+    if (appliedPatch != null) {
+      return new Data(appliedPatch.patchedText, false);
+    }
+    else {
+      return new Data(null, true);
+    }
+  }
+
+  @Nullable
+  public String getContent() {
+    return myData.getValue().content;
   }
 
   public boolean isPatchApplyFailed() {
-    return myPatchApplyFailed;
+    return myData.getValue().patchApplyFailed;
   }
 
   @NotNull
@@ -83,4 +89,14 @@ public class LazyPatchContentRevision implements ContentRevision {
       }
     };
   }
+
+  private static class Data {
+    @Nullable public final String content;
+    public final boolean patchApplyFailed;
+
+    public Data(@Nullable String content, boolean patchApplyFailed) {
+      this.content = content;
+      this.patchApplyFailed = patchApplyFailed;
+    }
+  }
 }