Revert "Files REST endpoint: Don't parse non-existing files"

This reverts commit 0520e08cb6. It broke
display of diffs for deleted files.

Also add a test to prevent it breaking again.

Bug: Issue 4450
Change-Id: Ib7546ed88c9cf7a5a0e16fc1eeff5a224feb4f25

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/revision/RevisionIT.java

@@ -52,7 +52,6 @@ import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.ETagView;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
-import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.reviewdb.client.Patch;
 import com.google.gerrit.server.change.GetRevisionActions;
@@ -567,16 +566,19 @@ public class RevisionIT extends AbstractDaemonTest {
   }
 
   @Test
-  public void diffNonExistingFile() throws Exception {
-    PushOneCommit.Result r = createChange();
-
-    exception.expect(ResourceNotFoundException.class);
-    exception.expectMessage("non-existing");
-    gApi.changes()
+  public void diffDeletedFile() throws Exception {
+    pushFactory.create(db, admin.getIdent(), testRepo)
+        .to("refs/heads/master");
+    PushOneCommit.Result r =
+        pushFactory.create(db, admin.getIdent(), testRepo)
+        .rm("refs/for/master");
+    DiffInfo diff = gApi.changes()
         .id(r.getChangeId())
         .revision(r.getCommit().name())
-        .file("non-existing")
+        .file(FILE_NAME)
         .diff();
+    assertThat(diff.metaA.lines).isEqualTo(1);
+    assertThat(diff.metaB).isNull();
   }
 
   @Test

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RevisionApi.java

@@ -47,7 +47,7 @@ public interface RevisionApi {
   Map<String, FileInfo> files() throws RestApiException;
   Map<String, FileInfo> files(String base) throws RestApiException;
   Map<String, FileInfo> files(int parentNum) throws RestApiException;
-  FileApi file(String path) throws RestApiException;
+  FileApi file(String path);
   MergeableInfo mergeable() throws RestApiException;
   MergeableInfo mergeableOtherBranches() throws RestApiException;
 

gerrit-server/src/main/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java

@@ -321,13 +321,9 @@ class RevisionApiImpl implements RevisionApi {
   }
 
   @Override
-  public FileApi file(String path) throws RestApiException {
-    try {
+  public FileApi file(String path) {
     return fileApi.create(files.parse(revision,
         IdString.fromDecoded(path)));
-    } catch (IOException e) {
-      throw new RestApiException("Cannot retrieve file", e);
-    }
   }
 
   @Override

gerrit-server/src/main/java/com/google/gerrit/server/change/Files.java

@@ -49,7 +49,6 @@ import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
-import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.filter.PathFilterGroup;
@@ -69,15 +68,11 @@ import java.util.concurrent.TimeUnit;
 public class Files implements ChildCollection<RevisionResource, FileResource> {
   private final DynamicMap<RestView<FileResource>> views;
   private final Provider<ListFiles> list;
-  private final GitRepositoryManager repoManager;
 
   @Inject
-  Files(DynamicMap<RestView<FileResource>> views,
-      Provider<ListFiles> list,
-      GitRepositoryManager repoManager) {
+  Files(DynamicMap<RestView<FileResource>> views, Provider<ListFiles> list) {
     this.views = views;
     this.list = list;
-    this.repoManager = repoManager;
   }
 
   @Override
@@ -91,21 +86,9 @@ public class Files implements ChildCollection<RevisionResource, FileResource> {
   }
 
   @Override
-  public FileResource parse(RevisionResource rev, IdString id)
-      throws ResourceNotFoundException, IOException {
-    if (Patch.COMMIT_MSG.equals(id.get())) {
+  public FileResource parse(RevisionResource rev, IdString id) {
     return new FileResource(rev, id.get());
   }
-    try (Repository repo = repoManager.openRepository(rev.getProject());
-        RevWalk rw = new RevWalk(repo)) {
-      RevTree tree = rw.parseTree(
-          ObjectId.fromString(rev.getPatchSet().getRevision().get()));
-      if (TreeWalk.forPath(repo, id.get(), tree) != null) {
-        return new FileResource(rev, id.get());
-      }
-    }
-    throw new ResourceNotFoundException(id);
-  }
 
   public static final class ListFiles implements RestReadView<RevisionResource> {
     private static final Logger log = LoggerFactory.getLogger(ListFiles.class);