1 files changed, 106 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PrerequisiteArtifacts.java b/src/main/java/com/google/devtools/build/lib/analysis/PrerequisiteArtifacts.java
new file mode 100644
index 0000000000..8932d5c67d
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+++ b/src/main/java/com/google/devtools/build/lib/analysis/PrerequisiteArtifacts.java
@@ -0,0 +1,106 @@
+// Copyright 2014 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.analysis;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Predicate;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.util.FileType;
+import com.google.devtools.build.lib.util.FileTypeSet;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+/**
+ * Contains a sequence of prerequisite artifacts and supplies methods for filtering and reporting
+ * errors on those artifacts.
+ */
+public final class PrerequisiteArtifacts {
+  private final RuleContext ruleContext;
+  private final String attributeName;
+  private final ImmutableList<Artifact> artifacts;
+
+  private PrerequisiteArtifacts(
+      RuleContext ruleContext, String attributeName, ImmutableList<Artifact> artifacts) {
+    this.ruleContext = Preconditions.checkNotNull(ruleContext);
+    this.attributeName = Preconditions.checkNotNull(attributeName);
+    this.artifacts = Preconditions.checkNotNull(artifacts);
+  }
+
+  static PrerequisiteArtifacts get(RuleContext ruleContext, String attributeName, Mode mode) {
+    Set<Artifact> result = new LinkedHashSet<>();
+    for (FileProvider target :
+        ruleContext.getPrerequisites(attributeName, mode, FileProvider.class)) {
+      Iterables.addAll(result, target.getFilesToBuild());
+    }
+    return new PrerequisiteArtifacts(ruleContext, attributeName, ImmutableList.copyOf(result));
+  }
+
+  /**
+   * Returns the artifacts this instance contains in an {@link ImmutableList}.
+   */
+  public ImmutableList<Artifact> list() {
+    return artifacts;
+  }
+
+  private PrerequisiteArtifacts filter(Predicate<String> fileType, boolean errorsForNonMatching) {
+    ImmutableList.Builder<Artifact> filtered = new ImmutableList.Builder<Artifact>();
+
+    for (Artifact artifact : artifacts) {
+      if (fileType.apply(artifact.getFilename())) {
+        filtered.add(artifact);
+      } else if (errorsForNonMatching) {
+        ruleContext.attributeError(
+            attributeName,
+            String.format("%s does not match expected type: %s", artifact, fileType));
+      }
+    }
+
+    return new PrerequisiteArtifacts(ruleContext, attributeName, filtered.build());
+  }
+
+  /**
+   * Returns an equivalent instance but only containing artifacts of the given type, reporting
+   * errors for non-matching artifacts.
+   */
+  public PrerequisiteArtifacts errorsForNonMatching(FileType fileType) {
+    return filter(fileType, /*errorsForNonMatching=*/true);
+  }
+
+  /**
+   * Returns an equivalent instance but only containing artifacts of the given types, reporting
+   * errors for non-matching artifacts.
+   */
+  public PrerequisiteArtifacts errorsForNonMatching(FileTypeSet fileTypeSet) {
+    return filter(fileTypeSet, /*errorsForNonMatching=*/true);
+  }
+
+  /**
+   * Returns an equivalent instance but only containing artifacts of the given type.
+   */
+  public PrerequisiteArtifacts filter(FileType fileType) {
+    return filter(fileType, /*errorsForNonMatching=*/false);
+  }
+
+  /**
+   * Returns an equivalent instance but only containing artifacts of the given types.
+   */
+  public PrerequisiteArtifacts filter(FileTypeSet fileTypeSet) {
+    return filter(fileTypeSet, /*errorsForNonMatching=*/false);
+  }
+}