Introduce PackageErrorMessageValue

This CL introduces a new intermediate SkyValue type,
PackageErrorMessageValue, to be used by RecursivePkgFunction.
RecursivePkgValue will now have a direct dep on
PackageErrorMessageValue rather than PackageValue.

RELNOTES: None
PiperOrigin-RevId: 193549158

1 files changed, 159 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageErrorMessageValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageErrorMessageValue.java
new file mode 100644
index 0000000000..9cd9d7961b
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageErrorMessageValue.java
@@ -0,0 +1,159 @@
+// Copyright 2018 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.skyframe;
+
+import com.google.common.collect.Interner;
+import com.google.devtools.build.lib.cmdline.PackageIdentifier;
+import com.google.devtools.build.lib.concurrent.BlazeInterners;
+import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
+import com.google.devtools.build.skyframe.AbstractSkyKey;
+import com.google.devtools.build.skyframe.SkyFunctionName;
+import com.google.devtools.build.skyframe.SkyKey;
+import com.google.devtools.build.skyframe.SkyValue;
+
+/**
+ * Encapsulates the errors, if any, encountered when loading a specific package.
+ *
+ * <p>This is a change-pruning-friendly convenience {@link SkyValue} for use cases where {@link
+ * Result} is sufficient.
+ */
+public abstract class PackageErrorMessageValue implements SkyValue {
+  /** Tri-state result of loading the package. */
+  enum Result {
+    /**
+     * There was no error loading the package and {@link
+     * com.google.devtools.build.lib.packages.Package#containsErrors} returned {@code false}.
+     */
+    NO_ERROR,
+
+    /**
+     * There was no error loading the package and {@link
+     * com.google.devtools.build.lib.packages.Package#containsErrors} returned {@code true}.
+     */
+    ERROR,
+
+    /**
+     * There was a {@link com.google.devtools.build.lib.packages.NoSuchPackageException} loading the
+     * package.
+     */
+    NO_SUCH_PACKAGE_EXCEPTION,
+  }
+
+  /** Returns the {@link Result} from loading the package. */
+  abstract Result getResult();
+
+  /**
+   * If {@code getResult().equals(NO_SUCH_PACKAGE_EXCEPTION)}, returns the error message from the
+   * {@link com.google.devtools.build.lib.packages.NoSuchPackageException} encountered.
+   */
+  abstract String getNoSuchPackageExceptionMessage();
+
+  static PackageErrorMessageValue ofPackageWithNoErrors() {
+    return NO_ERROR_VALUE;
+  }
+
+  static PackageErrorMessageValue ofPackageWithErrors() {
+    return ERROR_VALUE;
+  }
+
+  static PackageErrorMessageValue ofNoSuchPackageException(String errorMessage) {
+    return new NoSuchPackageExceptionValue(errorMessage);
+  }
+
+  static SkyKey key(PackageIdentifier pkgId) {
+    return Key.create(pkgId);
+  }
+
+  @AutoCodec.VisibleForSerialization
+  @AutoCodec
+  static class Key extends AbstractSkyKey<PackageIdentifier> {
+    private static final Interner<Key> interner = BlazeInterners.newWeakInterner();
+
+    private Key(PackageIdentifier arg) {
+      super(arg);
+    }
+
+    @AutoCodec.VisibleForSerialization
+    @AutoCodec.Instantiator
+    static Key create(PackageIdentifier arg) {
+      return interner.intern(new Key(arg));
+    }
+
+    @Override
+    public SkyFunctionName functionName() {
+      return SkyFunctions.PACKAGE_ERROR_MESSAGE;
+    }
+  }
+
+  @AutoCodec
+  static final PackageErrorMessageValue NO_ERROR_VALUE =
+      new PackageErrorMessageValue() {
+        @Override
+        Result getResult() {
+          return Result.NO_ERROR;
+        }
+
+        @Override
+        String getNoSuchPackageExceptionMessage() {
+          throw new IllegalStateException();
+        }
+      };
+
+  @AutoCodec
+  static final PackageErrorMessageValue ERROR_VALUE =
+      new PackageErrorMessageValue() {
+        @Override
+        Result getResult() {
+          return Result.ERROR;
+        }
+
+        @Override
+        String getNoSuchPackageExceptionMessage() {
+          throw new IllegalStateException();
+        }
+      };
+
+  @AutoCodec
+  static class NoSuchPackageExceptionValue extends PackageErrorMessageValue {
+    private final String errorMessage;
+
+    public NoSuchPackageExceptionValue(String errorMessage) {
+      this.errorMessage = errorMessage;
+    }
+
+    @Override
+    Result getResult() {
+      return Result.NO_SUCH_PACKAGE_EXCEPTION;
+    }
+
+    @Override
+    String getNoSuchPackageExceptionMessage() {
+      return errorMessage;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (!(obj instanceof NoSuchPackageExceptionValue)) {
+        return false;
+      }
+      NoSuchPackageExceptionValue other = (NoSuchPackageExceptionValue) obj;
+      return errorMessage.equals(other.errorMessage);
+    }
+
+    @Override
+    public int hashCode() {
+      return errorMessage.hashCode();
+    }
+  }
+}