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// Copyright 2014 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.base.Preconditions;
import com.google.common.collect.Interner;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.BlazeInterners;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.lib.syntax.BuildFileAST;
import com.google.devtools.build.skyframe.AbstractSkyKey;
import com.google.devtools.build.skyframe.NotComparableSkyValue;
import com.google.devtools.build.skyframe.SkyFunctionName;
/**
* A value that represents an AST file lookup result. There are two subclasses: one for the case
* where the file is found, and another for the case where the file is missing (but there are no
* other errors).
*/
// In practice, if a ASTFileLookupValue is re-computed (i.e. not changed pruned), then it will
// almost certainly be unequal to the previous value. This is because of (i) the change-pruning
// semantics of the PackageLookupValue dep and the FileValue dep; consider the latter: if the
// FileValue for the bzl file has changed, then the contents of the bzl file probably changed and
// (ii) we don't currently have skylark-semantic-equality in BuildFileAST, so two BuildFileAST
// instances representing two different contents of a bzl file will be different.
// TODO(bazel-team): Consider doing better here. As a pre-req, we would need
// skylark-semantic-equality in BuildFileAST, rather than equality naively based on the contents of
// the bzl file. For a concrete example, the contents of comment lines do not currently impact
// skylark semantics.
public abstract class ASTFileLookupValue implements NotComparableSkyValue {
public abstract boolean lookupSuccessful();
public abstract BuildFileAST getAST();
public abstract String getErrorMsg();
/** If the file is found, this class encapsulates the parsed AST. */
@AutoCodec.VisibleForSerialization
public static class ASTLookupWithFile extends ASTFileLookupValue {
private final BuildFileAST ast;
private ASTLookupWithFile(BuildFileAST ast) {
Preconditions.checkNotNull(ast);
this.ast = ast;
}
@Override
public boolean lookupSuccessful() {
return true;
}
@Override
public BuildFileAST getAST() {
return this.ast;
}
@Override
public String getErrorMsg() {
throw new IllegalStateException(
"attempted to retrieve unsuccessful lookup reason for successful lookup");
}
}
/** If the file isn't found, this class encapsulates a message with the reason. */
@AutoCodec.VisibleForSerialization
public static class ASTLookupNoFile extends ASTFileLookupValue {
private final String errorMsg;
private ASTLookupNoFile(String errorMsg) {
this.errorMsg = Preconditions.checkNotNull(errorMsg);
}
@Override
public boolean lookupSuccessful() {
return false;
}
@Override
public BuildFileAST getAST() {
throw new IllegalStateException("attempted to retrieve AST from an unsuccessful lookup");
}
@Override
public String getErrorMsg() {
return this.errorMsg;
}
}
static ASTFileLookupValue forBadPackage(Label fileLabel, String reason) {
return new ASTLookupNoFile(
String.format("Unable to load package for '%s': %s", fileLabel, reason));
}
static ASTFileLookupValue forBadFile(Label fileLabel) {
return new ASTLookupNoFile(
String.format("Unable to load file '%s': file doesn't exist or isn't a file", fileLabel));
}
public static ASTFileLookupValue withFile(BuildFileAST ast) {
return new ASTLookupWithFile(ast);
}
public static Key key(Label astFileLabel) {
return ASTFileLookupValue.Key.create(astFileLabel);
}
@AutoCodec.VisibleForSerialization
@AutoCodec
static class Key extends AbstractSkyKey<Label> {
private static final Interner<Key> interner = BlazeInterners.newWeakInterner();
private Key(Label arg) {
super(arg);
}
@AutoCodec.VisibleForSerialization
@AutoCodec.Instantiator
static Key create(Label arg) {
return interner.intern(new Key(arg));
}
@Override
public SkyFunctionName functionName() {
return SkyFunctions.AST_FILE_LOOKUP;
}
}
}
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