1 files changed, 177 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java
new file mode 100644
index 0000000000..6dcc224ed7
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+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java
@@ -0,0 +1,177 @@
+// 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.devtools.build.lib.packages.CachingPackageLocator;
+import com.google.devtools.build.lib.packages.RuleClassProvider;
+import com.google.devtools.build.lib.pkgcache.PathPackageLocator;
+import com.google.devtools.build.lib.syntax.BuildFileAST;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import com.google.devtools.build.lib.vfs.RootedPath;
+import com.google.devtools.build.skyframe.SkyFunction;
+import com.google.devtools.build.skyframe.SkyFunctionException;
+import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
+import com.google.devtools.build.skyframe.SkyKey;
+import com.google.devtools.build.skyframe.SkyValue;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicReference;
+
+import javax.annotation.Nullable;
+
+/**
+ * A SkyFunction for {@link ASTFileLookupValue}s. Tries to locate a file and load it as a
+ * syntax tree and cache the resulting {@link BuildFileAST}. If the file doesn't exist
+ * the function doesn't fail but returns a specific NO_FILE ASTLookupValue.
+ */
+public class ASTFileLookupFunction implements SkyFunction {
+
+  private abstract static class FileLookupResult {
+    /** Returns whether the file lookup was successful. */
+    public abstract boolean lookupSuccessful();
+
+    /** If {@code lookupSuccessful()}, returns the {@link RootedPath} to the file. */
+    public abstract RootedPath rootedPath();
+
+    static FileLookupResult noFile() {
+      return UnsuccessfulFileResult.INSTANCE;
+    }
+
+    static FileLookupResult file(RootedPath rootedPath) {
+      return new SuccessfulFileResult(rootedPath);
+    }
+
+    private static class SuccessfulFileResult extends FileLookupResult {
+      private final RootedPath rootedPath;
+
+      private SuccessfulFileResult(RootedPath rootedPath) {
+        this.rootedPath = rootedPath;
+      }
+
+      @Override
+      public boolean lookupSuccessful() {
+        return true;
+      }
+
+      @Override
+      public RootedPath rootedPath() {
+        return rootedPath;
+      }
+    }
+
+    private static class UnsuccessfulFileResult extends FileLookupResult {
+      private static final UnsuccessfulFileResult INSTANCE = new UnsuccessfulFileResult();
+      private UnsuccessfulFileResult() {
+      }
+
+      @Override
+      public boolean lookupSuccessful() {
+        return false;
+      }
+
+      @Override
+      public RootedPath rootedPath() {
+        throw new IllegalStateException("unsucessful lookup");
+      }
+    }
+  }
+
+  private final AtomicReference<PathPackageLocator> pkgLocator;
+  private final RuleClassProvider ruleClassProvider;
+  private final CachingPackageLocator packageManager;
+
+  public ASTFileLookupFunction(AtomicReference<PathPackageLocator> pkgLocator,
+      CachingPackageLocator packageManager,
+      RuleClassProvider ruleClassProvider) {
+    this.pkgLocator = pkgLocator;
+    this.packageManager = packageManager;
+    this.ruleClassProvider = ruleClassProvider;
+  }
+
+  @Override
+  public SkyValue compute(SkyKey skyKey, Environment env) throws SkyFunctionException,
+      InterruptedException {
+    PathFragment astFilePathFragment = (PathFragment) skyKey.argument();
+    FileLookupResult lookupResult = getASTFile(env, astFilePathFragment);
+    if (lookupResult == null) {
+      return null;
+    }
+
+    BuildFileAST ast = null;
+    if (!lookupResult.lookupSuccessful()) {
+      // Return the specific NO_FILE ASTLookupValue instance if no file was found.
+      return ASTFileLookupValue.NO_FILE;
+    } else {
+      Path path = lookupResult.rootedPath().asPath();
+      // Skylark files end with bzl.
+      boolean parseAsSkylark = astFilePathFragment.getPathString().endsWith(".bzl");
+      try {
+        ast = parseAsSkylark
+            ? BuildFileAST.parseSkylarkFile(path, env.getListener(),
+                packageManager, ruleClassProvider.getSkylarkValidationEnvironment().clone())
+            : BuildFileAST.parseBuildFile(path, env.getListener(),
+                packageManager, false);
+      } catch (IOException e) {
+        throw new ASTLookupFunctionException(new ErrorReadingSkylarkExtensionException(
+            e.getMessage()), Transience.TRANSIENT);
+      }
+    }
+
+    return new ASTFileLookupValue(ast);
+  }
+
+  private FileLookupResult getASTFile(Environment env, PathFragment astFilePathFragment)
+      throws ASTLookupFunctionException {
+    for (Path packagePathEntry : pkgLocator.get().getPathEntries()) {
+      RootedPath rootedPath = RootedPath.toRootedPath(packagePathEntry, astFilePathFragment);
+      SkyKey fileSkyKey = FileValue.key(rootedPath);
+      FileValue fileValue = null;
+      try {
+        fileValue = (FileValue) env.getValueOrThrow(fileSkyKey, IOException.class,
+            FileSymlinkCycleException.class, InconsistentFilesystemException.class);
+      } catch (IOException | FileSymlinkCycleException e) {
+        throw new ASTLookupFunctionException(new ErrorReadingSkylarkExtensionException(
+            e.getMessage()), Transience.PERSISTENT);
+      } catch (InconsistentFilesystemException e) {
+        throw new ASTLookupFunctionException(e, Transience.PERSISTENT);
+      }
+      if (fileValue == null) {
+        return null;
+      }
+      if (fileValue.isFile()) {
+        return FileLookupResult.file(rootedPath);
+      }
+    }
+    return FileLookupResult.noFile();
+  }
+
+  @Nullable
+  @Override
+  public String extractTag(SkyKey skyKey) {
+    return null;
+  }
+
+  private static final class ASTLookupFunctionException extends SkyFunctionException {
+    private ASTLookupFunctionException(ErrorReadingSkylarkExtensionException e,
+        Transience transience) {
+      super(e, transience);
+    }
+
+    private ASTLookupFunctionException(InconsistentFilesystemException e, Transience transience) {
+      super(e, transience);
+    }
+  }
+}