1 files changed, 249 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java
new file mode 100644
index 0000000000..c877d38263
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+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupValue.java
@@ -0,0 +1,249 @@
+// 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.skyframe;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.packages.PackageIdentifier;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import com.google.devtools.build.skyframe.SkyKey;
+import com.google.devtools.build.skyframe.SkyValue;
+
+/**
+ * A value that represents a package lookup result.
+ *
+ * <p>Package lookups will always produce a value. On success, the {@code #getRoot} returns the
+ * package path root under which the package resides and the package's BUILD file is guaranteed to
+ * exist; on failure, {@code #getErrorReason} and {@code #getErrorMsg} describe why the package
+ * doesn't exist.
+ *
+ * <p>Implementation detail: we use inheritance here to optimize for memory usage.
+ */
+abstract class PackageLookupValue implements SkyValue {
+
+  enum ErrorReason {
+    // There is no BUILD file.
+    NO_BUILD_FILE,
+
+    // The package name is invalid.
+    INVALID_PACKAGE_NAME,
+
+    // The package is considered deleted because of --deleted_packages.
+    DELETED_PACKAGE,
+
+    // The //external package could not be loaded, either because the WORKSPACE file could not be
+    // parsed or the packages it references cannot be loaded.
+    NO_EXTERNAL_PACKAGE
+  }
+
+  protected PackageLookupValue() {
+  }
+
+  public static PackageLookupValue success(Path root) {
+    return new SuccessfulPackageLookupValue(root);
+  }
+
+  public static PackageLookupValue noBuildFile() {
+    return NoBuildFilePackageLookupValue.INSTANCE;
+  }
+
+  public static PackageLookupValue noExternalPackage() {
+    return NoExternalPackageLookupValue.INSTANCE;
+  }
+
+  public static PackageLookupValue invalidPackageName(String errorMsg) {
+    return new InvalidNamePackageLookupValue(errorMsg);
+  }
+
+  public static PackageLookupValue deletedPackage() {
+    return DeletedPackageLookupValue.INSTANCE;
+  }
+
+  /**
+   * For a successful package lookup, returns the root (package path entry) that the package
+   * resides in.
+   */
+  public abstract Path getRoot();
+
+  /**
+   * Returns whether the package lookup was successful.
+   */
+  public abstract boolean packageExists();
+
+  /**
+   * For an unsuccessful package lookup, gets the reason why {@link #packageExists} returns
+   * {@code false}.
+   */
+  abstract ErrorReason getErrorReason();
+
+  /**
+   * For an unsuccessful package lookup, gets a detailed error message for {@link #getErrorReason}
+   * that is suitable for reporting to a user.
+   */
+  abstract String getErrorMsg();
+
+  static SkyKey key(PathFragment directory) {
+    Preconditions.checkArgument(!directory.isAbsolute(), directory);
+    return key(PackageIdentifier.createInDefaultRepo(directory));
+  }
+
+  static SkyKey key(PackageIdentifier pkgIdentifier) {
+    return new SkyKey(SkyFunctions.PACKAGE_LOOKUP, pkgIdentifier);
+  }
+
+  private static class SuccessfulPackageLookupValue extends PackageLookupValue {
+
+    private final Path root;
+
+    private SuccessfulPackageLookupValue(Path root) {
+      this.root = root;
+    }
+
+    @Override
+    public boolean packageExists() {
+      return true;
+    }
+
+    @Override
+    public Path getRoot() {
+      return root;
+    }
+
+    @Override
+    ErrorReason getErrorReason() {
+      throw new IllegalStateException();
+    }
+
+    @Override
+    String getErrorMsg() {
+      throw new IllegalStateException();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (!(obj instanceof SuccessfulPackageLookupValue)) {
+        return false;
+      }
+      SuccessfulPackageLookupValue other = (SuccessfulPackageLookupValue) obj;
+      return root.equals(other.root);
+    }
+
+    @Override
+    public int hashCode() {
+      return root.hashCode();
+    }
+  }
+
+  private abstract static class UnsuccessfulPackageLookupValue extends PackageLookupValue {
+
+    @Override
+    public boolean packageExists() {
+      return false;
+    }
+
+    @Override
+    public Path getRoot() {
+      throw new IllegalStateException();
+    }
+  }
+
+  private static class NoBuildFilePackageLookupValue extends UnsuccessfulPackageLookupValue {
+
+    public static final NoBuildFilePackageLookupValue INSTANCE =
+        new NoBuildFilePackageLookupValue();
+
+    private NoBuildFilePackageLookupValue() {
+    }
+
+    @Override
+    ErrorReason getErrorReason() {
+      return ErrorReason.NO_BUILD_FILE;
+    }
+
+    @Override
+    String getErrorMsg() {
+      return "BUILD file not found on package path";
+    }
+  }
+
+  private static class NoExternalPackageLookupValue extends UnsuccessfulPackageLookupValue {
+
+    public static final NoExternalPackageLookupValue INSTANCE =
+        new NoExternalPackageLookupValue();
+
+    private NoExternalPackageLookupValue() {
+    }
+
+    @Override
+    ErrorReason getErrorReason() {
+      return ErrorReason.NO_EXTERNAL_PACKAGE;
+    }
+
+    @Override
+    String getErrorMsg() {
+      return "Error loading the //external package";
+    }
+  }
+
+  private static class InvalidNamePackageLookupValue extends UnsuccessfulPackageLookupValue {
+
+    private final String errorMsg;
+
+    private InvalidNamePackageLookupValue(String errorMsg) {
+      this.errorMsg = errorMsg;
+    }
+
+    @Override
+    ErrorReason getErrorReason() {
+      return ErrorReason.INVALID_PACKAGE_NAME;
+    }
+
+    @Override
+    String getErrorMsg() {
+      return errorMsg;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (!(obj instanceof InvalidNamePackageLookupValue)) {
+        return false;
+      }
+      InvalidNamePackageLookupValue other = (InvalidNamePackageLookupValue) obj;
+      return errorMsg.equals(other.errorMsg);
+    }
+
+    @Override
+    public int hashCode() {
+      return errorMsg.hashCode();
+    }
+  }
+
+  private static class DeletedPackageLookupValue extends UnsuccessfulPackageLookupValue {
+
+    public static final DeletedPackageLookupValue INSTANCE = new DeletedPackageLookupValue();
+
+    private DeletedPackageLookupValue() {
+    }
+
+    @Override
+    ErrorReason getErrorReason() {
+      return ErrorReason.DELETED_PACKAGE;
+    }
+
+    @Override
+    String getErrorMsg() {
+      return "Package is considered deleted due to --deleted_packages";
+    }
+  }
+}