Update from Google.
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MOE_MIGRATED_REVID=85702957
diff --git a/src/main/java/com/google/devtools/build/lib/packages/EnvironmentGroup.java b/src/main/java/com/google/devtools/build/lib/packages/EnvironmentGroup.java
new file mode 100644
index 0000000..07da227
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/packages/EnvironmentGroup.java
@@ -0,0 +1,241 @@
+// 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.packages;
+
+import com.google.common.base.Predicate;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Sets;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.syntax.Label;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Model for the "environment_group' rule: the piece of Bazel's rule constraint system that binds
+ * thematically related environments together and determines which environments a rule supports
+ * by default. See {@link com.google.devtools.build.lib.analysis.constraints.ConstraintSemantics}
+ * for precise semantic details of how this information is used.
+ *
+ * <p>Note that "environment_group" is implemented as a loading-time function, not a rule. This is
+ * to support proper discovery of defaults: Say rule A has no explicit constraints and depends
+ * on rule B, which is explicitly constrained to environment ":bar". Since A declares nothing
+ * explicitly, it's implicitly constrained to DEFAULTS (whatever that is). Therefore, the
+ * dependency is only allowed if DEFAULTS doesn't include environments beyond ":bar". To figure
+ * that out, we need to be able to look up the environment group for ":bar", which is what this
+ * class provides.
+ *
+ * <p>If we implemented this as a rule, we'd have to provide that lookup via rule dependencies,
+ * e.g. something like:
+ *
+ * <code>
+ * environment(
+ * name = 'bar',
+ * group = [':sample_environments'],
+ * is_default = 1
+ * )
+ * </code>
+ *
+ * <p>But this won't work. This would let us find the environment group for ":bar", but the only way
+ * to determine what other environments belong to the group is to have the group somehow reference
+ * them. That would produce circular dependencies in the build graph, which is no good.
+ */
+@Immutable
+public class EnvironmentGroup implements Target {
+ private final Label label;
+ private final Location location;
+ private final Package containingPackage;
+ private final Set<Label> environments;
+ private final Set<Label> defaults;
+
+ /**
+ * Predicate that matches labels from a different package than the initialized package.
+ */
+ private static final class DifferentPackage implements Predicate<Label> {
+ private final Package containingPackage;
+
+ private DifferentPackage(Package containingPackage) {
+ this.containingPackage = containingPackage;
+ }
+
+ @Override
+ public boolean apply(Label environment) {
+ return !environment.getPackageName().equals(containingPackage.getName());
+ }
+ }
+
+ /**
+ * Instantiates a new group without verifying the soundness of its contents. See the validation
+ * methods below for appropriate checks.
+ *
+ * @param label the build label identifying this group
+ * @param pkg the package this group belongs to
+ * @param environments the set of environments that belong to this group
+ * @param defaults the environments a rule implicitly supports unless otherwise specified
+ * @param location location in the BUILD file of this group
+ */
+ EnvironmentGroup(Label label, Package pkg, final List<Label> environments, List<Label> defaults,
+ Location location) {
+ this.label = label;
+ this.location = location;
+ this.containingPackage = pkg;
+ this.environments = ImmutableSet.copyOf(environments);
+ this.defaults = ImmutableSet.copyOf(defaults);
+ }
+
+ /**
+ * Checks that all environments declared by this group are in the same package as the group (so
+ * we can perform an environment --> environment_group lookup and know the package is available)
+ * and checks that all defaults are legitimate members of the group.
+ *
+ * <p>Does <b>not</b> check that the referenced environments exist (see
+ * {@link #checkEnvironmentsExist).
+ *
+ * @return a list of validation errors that occurred
+ */
+ List<Event> validateMembership() {
+ List<Event> events = new ArrayList<>();
+
+ // All environments should belong to the same package as this group.
+ for (Label environment :
+ Iterables.filter(environments, new DifferentPackage(containingPackage))) {
+ events.add(Event.error(location,
+ environment + " is not in the same package as group " + label));
+ }
+
+ // The defaults must be a subset of the member environments.
+ for (Label unknownDefault : Sets.difference(defaults, environments)) {
+ events.add(Event.error(location, "default " + unknownDefault + " is not a "
+ + "declared environment for group " + getLabel()));
+ }
+
+ return events;
+ }
+
+ /**
+ * Given the set of targets in this group's package, checks that all of the group's declared
+ * environments are part of that set (i.e. the group doesn't reference non-existant labels).
+ *
+ * @param pkgTargets mapping from label name to target instance for this group's package
+ * @return a list of validation errors that occurred
+ */
+ List<Event> checkEnvironmentsExist(Map<String, Target> pkgTargets) {
+ List<Event> events = new ArrayList<>();
+ for (Label envName : environments) {
+ Target env = pkgTargets.get(envName.getName());
+ if (env == null) {
+ events.add(Event.error(location, "environment " + envName + " does not exist"));
+ } else if (!env.getTargetKind().equals("environment rule")) {
+ events.add(Event.error(location, env.getLabel() + " is not a valid environment"));
+ }
+ }
+ return events;
+ }
+
+ /**
+ * Returns the environments that belong to this group.
+ */
+ public Set<Label> getEnvironments() {
+ return environments;
+ }
+
+ /**
+ * Returns the environments a rule supports by default, i.e. if it has no explicit references to
+ * environments in this group.
+ */
+ public Set<Label> getDefaults() {
+ return defaults;
+ }
+
+ /**
+ * Determines whether or not an environment is a default. Returns false if the environment
+ * doesn't belong to this group.
+ */
+ public boolean isDefault(Label environment) {
+ return defaults.contains(environment);
+ }
+
+ @Override
+ public Label getLabel() {
+ return label;
+ }
+
+ @Override
+ public String getName() {
+ return label.getName();
+ }
+
+ @Override
+ public Package getPackage() {
+ return containingPackage;
+ }
+
+ @Override
+ public String getTargetKind() {
+ return targetKind();
+ }
+
+ @Override
+ public Rule getAssociatedRule() {
+ return null;
+ }
+
+ @Override
+ public License getLicense() {
+ return License.NO_LICENSE;
+ }
+
+ @Override
+ public Location getLocation() {
+ return location;
+ }
+
+ @Override
+ public String toString() {
+ return targetKind() + " " + getLabel();
+ }
+
+ @Override
+ public Set<License.DistributionType> getDistributions() {
+ return Collections.emptySet();
+ }
+
+ @Override
+ public RuleVisibility getVisibility() {
+ return ConstantRuleVisibility.PRIVATE; // No rule should be referencing an environment_group.
+ }
+
+ public static String targetKind() {
+ return "environment group";
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ // In a distributed implementation these may not be the same object.
+ if (o == this) {
+ return true;
+ } else if (!(o instanceof EnvironmentGroup)) {
+ return false;
+ } else {
+ return ((EnvironmentGroup) o).getLabel().equals(getLabel());
+ }
+ }
+}
