Sync only allowed external workspace target from project

Require external target directory within project to be listed
in directories section of project view file. Also introduces
registry key "bazel.cpp.sync.external.targets.from.directories"
which can be used to disable mentioned external targets sync.

base/src/com/google/idea/blaze/base/sync/projectview/ProjectViewTargetImportFilter.java

@@ -19,6 +19,7 @@
 import com.google.idea.blaze.base.ideinfo.Tags;
 import com.google.idea.blaze.base.ideinfo.TargetIdeInfo;
 import com.google.idea.blaze.base.model.primitives.Label;
+import com.google.idea.blaze.base.model.primitives.WorkspacePath;
 import com.google.idea.blaze.base.model.primitives.WorkspaceRoot;
 import com.google.idea.blaze.base.projectview.ProjectViewSet;
 import com.google.idea.blaze.base.projectview.section.sections.ExcludeTargetSection;
@@ -45,6 +46,10 @@ public boolean isSourceTarget(TargetIdeInfo target) {
     return importRoots.importAsSource(target.getKey().getLabel()) && !importTargetOutput(target);
   }
 
+  public boolean containsWorkspacePath(WorkspacePath workspacePath) {
+    return importRoots.containsWorkspacePath(workspacePath);
+  }
+
   private boolean importTargetOutput(TargetIdeInfo target) {
     return target.getTags().contains(Tags.TARGET_TAG_IMPORT_TARGET_OUTPUT)
         || target.getTags().contains(Tags.TARGET_TAG_IMPORT_AS_LIBRARY_LEGACY)

cpp/src/META-INF/blaze-cpp.xml

@@ -59,6 +59,7 @@
                     overrides="true"
     />
     <registryKey defaultValue="false" description="Disable absolute path trimming in debug clang builds" key="bazel.trim.absolute.path.disabled"/>
+    <registryKey defaultValue="true" description="Allow external targets from source directories be imported in" key="bazel.cpp.sync.external.targets.from.directories"/>
     <applicationService serviceInterface="com.google.idea.blaze.cpp.CompilerVersionChecker"
                         serviceImplementation="com.google.idea.blaze.cpp.CompilerVersionCheckerImpl"/>
     <applicationService serviceInterface="com.google.idea.blaze.cpp.CompilerWrapperProvider"

cpp/src/com/google/idea/blaze/cpp/BlazeConfigurationResolver.java

@@ -30,6 +30,7 @@
 import com.google.idea.blaze.base.ideinfo.TargetKey;
 import com.google.idea.blaze.base.model.BlazeProjectData;
 import com.google.idea.blaze.base.model.primitives.ExecutionRootPath;
+import com.google.idea.blaze.base.model.primitives.WorkspacePath;
 import com.google.idea.blaze.base.model.primitives.WorkspaceRoot;
 import com.google.idea.blaze.base.projectview.ProjectViewSet;
 import com.google.idea.blaze.base.scope.BlazeContext;
@@ -47,6 +48,7 @@
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.io.FileUtilRt;
+import com.intellij.openapi.util.registry.Registry;
 import java.io.IOException;
 import java.nio.file.Path;
 import java.util.Optional;
@@ -65,6 +67,8 @@
 import java.util.stream.Collectors;
 
 final class BlazeConfigurationResolver {
+  static final String SYNC_EXTERNAL_TARGETS_FROM_DIRECTORIES_KEY = "bazel.cpp.sync.external.targets.from.directories";
+
   private static final Logger logger = Logger.getInstance(BlazeConfigurationResolver.class);
 
   private final Project project;
@@ -142,20 +146,22 @@ private static ImmutableMap<String, String> getTargetToVersionMap(ImmutableMap<T
 
   private static Predicate<TargetIdeInfo> getTargetFilter(
       ProjectViewTargetImportFilter projectViewFilter,
-      Project project, WorkspacePathResolver workspacePathResolver) {
+      Project project,
+      WorkspacePathResolver workspacePathResolver) {
     return target -> {
-      boolean targetFromExternalWorkspaceInProject = isExternalWorkspaceTargetInProject(target,
-          project,
-          workspacePathResolver
-      );
+      WorkspacePath pathForExternalTarget = getWorkspacePathForExternalTarget(target, project, workspacePathResolver);
+
+      boolean allowExternalTargetSync =
+          Registry.is(SYNC_EXTERNAL_TARGETS_FROM_DIRECTORIES_KEY) && pathForExternalTarget != null;
 
       return target.getcIdeInfo() != null
-          && (targetFromExternalWorkspaceInProject || projectViewFilter.isSourceTarget(target))
+          && (projectViewFilter.isSourceTarget(target) ||
+            allowExternalTargetSync && projectViewFilter.containsWorkspacePath(pathForExternalTarget))
           && containsCompiledSources(target);
     };
   }
 
-  private static boolean isExternalWorkspaceTargetInProject(
+  private static WorkspacePath getWorkspacePathForExternalTarget(
       TargetIdeInfo target,
       Project project,
       WorkspacePathResolver workspacePathResolver) {
@@ -166,15 +172,13 @@ private static boolean isExternalWorkspaceTargetInProject(
       if (externalWorkspace != null) {
         try {
           Path externalWorkspaceRealPath = externalWorkspace.directory().toPath().toRealPath();
-          if (workspacePathResolver.getWorkspacePath(externalWorkspaceRealPath.toFile()) != null) {
-            return true;
-          }
+          return workspacePathResolver.getWorkspacePath(externalWorkspaceRealPath.toFile());
         } catch (IOException ioException) {
           logger.warn("Failed to resolve real external workspace location", ioException);
         }
       }
     }
-    return false;
+    return null;
   }
 
   private static boolean containsCompiledSources(TargetIdeInfo target) {

cpp/tests/unittests/com/google/idea/blaze/cpp/BlazeConfigurationResolverTest.java

@@ -66,6 +66,7 @@
 import com.intellij.openapi.extensions.impl.ExtensionPointImpl;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.progress.impl.ProgressManagerImpl;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.vfs.LocalFileSystem;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.openapi.vfs.VirtualFileManager;
@@ -116,6 +117,8 @@ protected void initTest(Container applicationServices, Container projectServices
         VirtualFileSystemProvider.class, mock(VirtualFileSystemProvider.class));
     when(VirtualFileSystemProvider.getInstance().getSystem()).thenReturn(mockFileSystem);
 
+    Registry.get(BlazeConfigurationResolver.SYNC_EXTERNAL_TARGETS_FROM_DIRECTORIES_KEY).setValue(true);
+
     ExtensionPointImpl<Kind.Provider> ep =
         registerExtensionPoint(Kind.Provider.EP_NAME, Kind.Provider.class);
     ep.registerExtension(new CppBlazeRules());
@@ -796,7 +799,10 @@ public void multipleToolchainsNoIssue() {
 
   @Test
   public void testExternalDependencyResolvedWhenIsPartOfProject() throws IOException {
-    ProjectView projectView = projectView(directories("test"), targets("//test:target"));
+    ProjectView projectView = projectView(
+        directories("test", "external_dependency"),
+        targets("//test:target"));
+
     TargetMap targetMap =
         TargetMapBuilder.builder()
             .addTarget(createCcToolchain())

cpp/tests/unittests/com/google/idea/blaze/cpp/BlazeResolveConfigurationEquivalenceTest.java

@@ -63,6 +63,7 @@
 import com.intellij.openapi.extensions.impl.ExtensionPointImpl;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.progress.impl.ProgressManagerImpl;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.vfs.LocalFileSystem;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.openapi.vfs.VirtualFileManager;
@@ -116,6 +117,8 @@ protected void initTest(Container applicationServices, Container projectServices
     projectServices.register(
         BlazeImportSettingsManager.class, new BlazeImportSettingsManager(project));
 
+    Registry.get(BlazeConfigurationResolver.SYNC_EXTERNAL_TARGETS_FROM_DIRECTORIES_KEY).setValue(true);
+
     BlazeImportSettingsManager.getInstance(getProject())
         .setImportSettings(
             new BlazeImportSettings(