Fixed NPE in StagingView if no repository is selected

This is a follow up on https://git.eclipse.org/r/54672.

If Staging view was opened without selecting any repository, changing
any preference in any of the Git preference pages caused NPE in
IndexDiffCache.getIndexDiffCacheEntry(Repository).

Marked currentRepository field as Nullable and fixed all other possible
NPE places. 

Enabled org.eclipse.jdt.core.compiler.problem.nullUncheckedConversion to
show warnings if a value with unknown nullness is used where a NonNull
value is required.

Change-Id: Iab52940a67fe0205e16fa6bc5027948a4d819ff2
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

3 files changed, 28 insertions, 14 deletions

diff --git a/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/indexdiff/IndexDiffCache.java b/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/indexdiff/IndexDiffCache.java
index 98cd5319f2..5fa3fe8629 100644
--- a/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/indexdiff/IndexDiffCache.java
+++ b/org.eclipse.egit.core/src/org/eclipse/egit/core/internal/indexdiff/IndexDiffCache.java
@@ -16,6 +16,7 @@ import java.util.Set;
 import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.egit.core.Activator;
 import org.eclipse.egit.core.JobFamilies;
+import org.eclipse.jdt.annotation.NonNull;
 import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.jgit.lib.IndexDiff;
 import org.eclipse.jgit.lib.Repository;
@@ -44,7 +45,7 @@ public class IndexDiffCache {
 	 * @return cache entry
 	 */
 	@Nullable
-	public IndexDiffCacheEntry getIndexDiffCacheEntry(Repository repository) {
+	public IndexDiffCacheEntry getIndexDiffCacheEntry(@NonNull Repository repository) {
 		IndexDiffCacheEntry entry;
 		synchronized (entries) {
 			entry = entries.get(repository);
diff --git a/org.eclipse.egit.ui/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.egit.ui/.settings/org.eclipse.jdt.core.prefs
index 2b21a346ed..5939995770 100644
--- a/org.eclipse.egit.ui/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.egit.ui/.settings/org.eclipse.jdt.core.prefs
@@ -67,7 +67,7 @@ org.eclipse.jdt.core.compiler.problem.nonnullParameterAnnotationDropped=warning
 org.eclipse.jdt.core.compiler.problem.nullAnnotationInferenceConflict=error
 org.eclipse.jdt.core.compiler.problem.nullReference=error
 org.eclipse.jdt.core.compiler.problem.nullSpecViolation=error
-org.eclipse.jdt.core.compiler.problem.nullUncheckedConversion=ignore
+org.eclipse.jdt.core.compiler.problem.nullUncheckedConversion=warning
 org.eclipse.jdt.core.compiler.problem.overridingPackageDefaultMethod=warning
 org.eclipse.jdt.core.compiler.problem.parameterAssignment=ignore
 org.eclipse.jdt.core.compiler.problem.possibleAccidentalBooleanAssignment=error
diff --git a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/staging/StagingView.java b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/staging/StagingView.java
index 5b7b001c0e..43e954bea0 100644
--- a/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/staging/StagingView.java
+++ b/org.eclipse.egit.ui/src/org/eclipse/egit/ui/internal/staging/StagingView.java
@@ -85,6 +85,7 @@ import org.eclipse.egit.ui.internal.dialogs.SpellcheckableMessageArea;
 import org.eclipse.egit.ui.internal.operations.DeletePathsOperationUI;
 import org.eclipse.egit.ui.internal.operations.IgnoreOperationUI;
 import org.eclipse.egit.ui.internal.repository.tree.RepositoryTreeNode;
+import org.eclipse.jdt.annotation.NonNull;
 import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.jface.action.Action;
 import org.eclipse.jface.action.ControlContribution;
@@ -277,6 +278,7 @@ public class StagingView extends ViewPart implements IShowInSource {
 
 	private Action compareModeAction;
 
+	@Nullable
 	private Repository currentRepository;
 
 	private Presentation presentation = Presentation.LIST;
@@ -1114,8 +1116,11 @@ public class StagingView extends ViewPart implements IShowInSource {
 	}
 
 	private boolean commitAndPushEnabled(boolean commitEnabled) {
-		return commitEnabled
-				&& !currentRepository.getRepositoryState().isRebasing();
+		Repository repo = currentRepository;
+		if (repo == null) {
+			return false;
+		}
+		return commitEnabled && !repo.getRepositoryState().isRebasing();
 	}
 
 	private void updateIgnoreErrorsButtonVisibility() {
@@ -1146,7 +1151,12 @@ public class StagingView extends ViewPart implements IShowInSource {
 		if (cacheEntry != null) {
 			indexDiff = cacheEntry.getIndexDiff();
 		} else {
-			indexDiff = doReload(currentRepository);
+			Repository repo = currentRepository;
+			if (repo == null) {
+				indexDiff = null;
+			} else {
+				indexDiff = doReload(repo);
+			}
 		}
 		boolean indexDiffAvailable = indexDiffAvailable(indexDiff);
 		boolean noConflicts = noConflicts(indexDiff);
@@ -1473,12 +1483,13 @@ public class StagingView extends ViewPart implements IShowInSource {
 	}
 
 	private void enableAuthorText(boolean enabled) {
-		if (currentRepository != null
-				&& currentRepository.getRepositoryState().equals(
-				RepositoryState.CHERRY_PICKING_RESOLVED))
+		Repository repo = currentRepository;
+		if (repo != null && repo.getRepositoryState()
+				.equals(RepositoryState.CHERRY_PICKING_RESOLVED)) {
 			authorText.setEnabled(false);
-		else
+		} else {
 			authorText.setEnabled(enabled);
+		}
 	}
 
 	private void updateToolbar() {
@@ -2204,14 +2215,16 @@ public class StagingView extends ViewPart implements IShowInSource {
 	}
 
 	private void openSelectionInEditor(ISelection s) {
-		if (s.isEmpty() || !(s instanceof IStructuredSelection))
+		Repository repo = currentRepository;
+		if (repo == null || s.isEmpty() || !(s instanceof IStructuredSelection)) {
 			return;
+		}
 		final IStructuredSelection iss = (IStructuredSelection) s;
 		for (Object element : iss.toList()) {
 			if (element instanceof StagingEntry) {
 				StagingEntry entry = (StagingEntry) element;
 				String relativePath = entry.getPath();
-				String path = new Path(currentRepository.getWorkTree()
+				String path = new Path(repo.getWorkTree()
 						.getAbsolutePath()).append(relativePath)
 						.toOSString();
 				openFileInEditor(path);
@@ -2730,7 +2743,7 @@ public class StagingView extends ViewPart implements IShowInSource {
 						: false;
 	}
 
-	private IndexDiffData doReload(final Repository repository) {
+	private IndexDiffData doReload(@NonNull	final Repository repository) {
 		IndexDiffCacheEntry entry = org.eclipse.egit.core.Activator.getDefault()
 				.getIndexDiffCache().getIndexDiffCacheEntry(repository);
 
@@ -2893,8 +2906,8 @@ public class StagingView extends ViewPart implements IShowInSource {
 			return false;
 
 		String chIdLine = "Change-Id: I" + ObjectId.zeroId().name(); //$NON-NLS-1$
-
-		if (GerritUtil.getCreateChangeId(currentRepository.getConfig())
+		Repository repo = currentRepository;
+		if (repo != null && GerritUtil.getCreateChangeId(repo.getConfig())
 				&& commitMessageComponent.getCreateChangeId()) {
 			if (message.trim().equals(chIdLine))
 				return false;