1 files changed, 162 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java b/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java
new file mode 100644
index 0000000000..78a963ea8f
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+++ b/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java
@@ -0,0 +1,162 @@
+// Copyright 2016 The Bazel Authors. 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.collect.ImmutableSet;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.util.Preconditions;
+import java.util.ArrayList;
+import java.util.Objects;
+
+/**
+ * Captures the the set of providers rules and aspects can advertise.
+ * It is either of:
+ * <ul>
+ *    <li>a set of native and skylark providers</li>
+ *    <li>"can have any provider" set that alias rules have.</li>
+ * </ul>
+ *
+ * <p>
+ * Native providers should in theory only contain subclasses of
+ * {@link com.google.devtools.build.lib.analysis.TransitiveInfoProvider}, but
+ * our current dependency structure does not allow a reference to that class here.
+ * </p>
+ */
+// todo(dslomov,vladmos): support declared providers
+@Immutable
+public final class AdvertisedProviderSet {
+  private final boolean canHaveAnyProvider;
+  private final ImmutableSet<Class<?>> nativeProviders;
+  // todo(dslomov,vladmos): support declared providers
+  private final ImmutableSet<String> skylarkProviders;
+
+  private AdvertisedProviderSet(boolean canHaveAnyProvider,
+      ImmutableSet<Class<?>> nativeProviders,
+      ImmutableSet<String> skylarkProviders) {
+    this.canHaveAnyProvider = canHaveAnyProvider;
+    this.nativeProviders = nativeProviders;
+    this.skylarkProviders = skylarkProviders;
+  }
+
+  public static final AdvertisedProviderSet ANY =
+      new AdvertisedProviderSet(true,
+          ImmutableSet.<Class<?>>of(),
+          ImmutableSet.<String>of());
+  public static final AdvertisedProviderSet EMPTY =
+      new AdvertisedProviderSet(false,
+          ImmutableSet.<Class<?>>of(),
+          ImmutableSet.<String>of());
+
+  public static AdvertisedProviderSet create(
+      ImmutableSet<Class<?>> nativeProviders,
+      ImmutableSet<String> skylarkProviders) {
+    if (nativeProviders.isEmpty() && skylarkProviders.isEmpty()) {
+      return EMPTY;
+    }
+    return new AdvertisedProviderSet(false, nativeProviders, skylarkProviders);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(canHaveAnyProvider, nativeProviders, skylarkProviders);
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) {
+      return true;
+    }
+
+    if (!(obj instanceof AdvertisedProviderSet)) {
+      return false;
+    }
+
+    AdvertisedProviderSet that = (AdvertisedProviderSet) obj;
+    return Objects.equals(this.canHaveAnyProvider, that.canHaveAnyProvider)
+        && Objects.equals(this.nativeProviders, that.nativeProviders)
+        && Objects.equals(this.skylarkProviders, that.skylarkProviders);
+  }
+
+  /** Checks whether the rule can have any provider.
+   *
+   *  Used for alias rules.
+   */
+  public boolean canHaveAnyProvider() {
+    return canHaveAnyProvider;
+  }
+
+  /**
+   * Get all advertised native providers.
+   */
+  public ImmutableSet<Class<?>> getNativeProviders() {
+    return nativeProviders;
+  }
+
+  /**
+   * Get all advertised Skylark providers.
+   */
+  public ImmutableSet<String> getSkylarkProviders() {
+    return skylarkProviders;
+  }
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  /** Builder for {@link AdvertisedProviderSet} */
+  public static class Builder {
+    private boolean canHaveAnyProvider;
+    private final ArrayList<Class<?>> nativeProviders;
+    private final ArrayList<String> skylarkProviders;
+    private Builder() {
+      nativeProviders = new ArrayList<>();
+      skylarkProviders = new ArrayList<>();
+    }
+
+    /**
+     * Advertise all providers inherited from a parent rule.
+     */
+    public Builder addParent(AdvertisedProviderSet parentSet) {
+      Preconditions.checkState(!canHaveAnyProvider, "Alias rules inherit from no other rules");
+      Preconditions.checkState(!parentSet.canHaveAnyProvider(),
+          "Cannot inherit from alias rules");
+      nativeProviders.addAll(parentSet.getNativeProviders());
+      skylarkProviders.addAll(parentSet.getSkylarkProviders());
+      return this;
+    }
+
+    public Builder addNative(Class<?> nativeProvider) {
+      this.nativeProviders.add(nativeProvider);
+      return this;
+    }
+
+    public void canHaveAnyProvider() {
+      Preconditions.checkState(nativeProviders.isEmpty() && skylarkProviders.isEmpty());
+      this.canHaveAnyProvider = true;
+    }
+
+    public AdvertisedProviderSet build() {
+      if (canHaveAnyProvider) {
+        Preconditions.checkState(nativeProviders.isEmpty() && skylarkProviders.isEmpty());
+        return ANY;
+      }
+      return AdvertisedProviderSet.create(
+          ImmutableSet.copyOf(nativeProviders), ImmutableSet.copyOf(skylarkProviders));
+    }
+
+    public void addSkylark(String providerName) {
+      skylarkProviders.add(providerName);
+    }
+  }
+}