On-the-fly target pattern resolution in SkyQueryEnvironment

Moves pattern resolving logic from TargetPatternFunction.Resolver to
a top level class. Adds a layer of abstraction to the Resolver
implementation enabling it to be backed by either an Environment or
a Graph, for use in SkyFunction evaluation or on-the-fly evaluation,
respectively. Finally, SkyQueryEnvironment#preloadOrThrow now checks
to see if each target pattern exists in the graph, and any that
don't will be resolved on-the-fly.

--
MOS_MIGRATED_REVID=88861201

1 files changed, 116 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java b/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java
new file mode 100644
index 0000000000..901e8775c0
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java
@@ -0,0 +1,116 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.skyframe;
+
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.packages.NoSuchPackageException;
+import com.google.devtools.build.lib.packages.NoSuchTargetException;
+import com.google.devtools.build.lib.packages.Package;
+import com.google.devtools.build.lib.packages.PackageIdentifier;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.pkgcache.RecursivePackageProvider;
+import com.google.devtools.build.lib.syntax.Label;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import com.google.devtools.build.lib.vfs.RootedPath;
+import com.google.devtools.build.skyframe.SkyFunction.Environment;
+import com.google.devtools.build.skyframe.SkyKey;
+
+/**
+ * A {@link RecursivePackageProvider} backed by an {@link Environment}. Its methods
+ * may throw {@link MissingDepException} if the package values this depends on haven't been
+ * calculated and added to its environment.
+ *
+ * <p>That exception will be caught by the compute method in {@link TargetPatternFunction}, which
+ * then returns {@code null} in accordance with the skyframe missing dependency policy.
+ */
+public final class EnvironmentBackedRecursivePackageProvider implements RecursivePackageProvider {
+
+  private final Environment env;
+
+  public EnvironmentBackedRecursivePackageProvider(Environment env) {
+    this.env = env;
+  }
+
+  @Override
+  public Package getPackage(EventHandler eventHandler, PackageIdentifier packageName)
+      throws NoSuchPackageException, MissingDepException {
+    SkyKey pkgKey = PackageValue.key(packageName);
+    Package pkg;
+    try {
+      PackageValue pkgValue =
+          (PackageValue) env.getValueOrThrow(pkgKey, NoSuchPackageException.class);
+      if (pkgValue == null) {
+        throw new MissingDepException();
+      }
+      pkg = pkgValue.getPackage();
+    } catch (NoSuchPackageException e) {
+      pkg = e.getPackage();
+      if (pkg == null) {
+        throw e;
+      }
+    }
+    return pkg;
+  }
+
+  @Override
+  public boolean isPackage(EventHandler eventHandler, String packageName)
+      throws MissingDepException {
+    SkyKey packageLookupKey = PackageLookupValue.key(new PathFragment(packageName));
+    try {
+      PackageLookupValue packageLookupValue =
+          (PackageLookupValue) env.getValueOrThrow(packageLookupKey, NoSuchPackageException.class,
+              InconsistentFilesystemException.class);
+      if (packageLookupValue == null) {
+        throw new MissingDepException();
+      }
+      return packageLookupValue.packageExists();
+    } catch (NoSuchPackageException | InconsistentFilesystemException e) {
+      eventHandler.handle(Event.error(e.getMessage()));
+      return false;
+    }
+  }
+
+  @Override
+  public Iterable<PathFragment> getPackagesUnderDirectory(RootedPath directory)
+      throws MissingDepException {
+    RecursivePkgValue lookup = (RecursivePkgValue) env.getValue(RecursivePkgValue.key(directory));
+    if (lookup == null) {
+      // Typically a null value from Environment.getValue(k) means that either the key k is missing
+      // a dependency or an exception was thrown during evaluation of k. Here, if this getValue
+      // call returns null, it can only mean a missing dependency, because
+      // RecursivePkgFunction#compute never throws.
+      throw new MissingDepException();
+    }
+    // TODO(bazel-team): Make RecursivePkgValue return NestedSet<PathFragment> so this transform is
+    // unnecessary.
+    return Iterables.transform(lookup.getPackages(), PathFragment.TO_PATH_FRAGMENT);
+  }
+
+  @Override
+  public Target getTarget(EventHandler eventHandler, Label label) throws NoSuchPackageException,
+      NoSuchTargetException, MissingDepException {
+    return getPackage(eventHandler, label.getPackageIdentifier()).getTarget(label.getName());
+  }
+
+  /**
+   * Indicates that a missing dependency is needed before target parsing can proceed. Currently
+   * used only in skyframe to notify the framework of missing dependencies. Caught by the compute
+   * method in {@link com.google.devtools.build.lib.skyframe.TargetPatternFunction}, which then
+   * returns null in accordance with the skyframe missing dependency policy.
+   */
+  class MissingDepException extends RuntimeException {
+  }
+}