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// Copyright 2015 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 static com.google.common.base.Preconditions.checkState;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.actions.FilesetOutputSymlink;
import com.google.devtools.build.lib.actions.FilesetTraversalParams;
import com.google.devtools.build.lib.actions.FilesetTraversalParams.DirectTraversal;
import com.google.devtools.build.lib.actions.HasDigest;
import com.google.devtools.build.lib.skyframe.RecursiveFilesystemTraversalFunction.DanglingSymlinkException;
import com.google.devtools.build.lib.skyframe.RecursiveFilesystemTraversalFunction.RecursiveFilesystemTraversalException;
import com.google.devtools.build.lib.skyframe.RecursiveFilesystemTraversalValue.ResolvedFile;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyFunctionException;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.function.Function;
import javax.annotation.Nullable;
/** SkyFunction for {@link FilesetEntryValue}. */
public final class FilesetEntryFunction implements SkyFunction {
private static final class FilesetEntryFunctionException extends SkyFunctionException {
FilesetEntryFunctionException(RecursiveFilesystemTraversalException e) {
super(e, Transience.PERSISTENT);
}
}
private final Function<String, Path> getExecRoot;
public FilesetEntryFunction(Function<String, Path> getExecRoot) {
this.getExecRoot = getExecRoot;
}
@Override
@Nullable
public SkyValue compute(SkyKey key, Environment env)
throws FilesetEntryFunctionException, InterruptedException {
WorkspaceNameValue workspaceNameValue =
(WorkspaceNameValue) env.getValue(WorkspaceNameValue.key());
if (workspaceNameValue == null) {
return null;
}
FilesetTraversalParams params = checkParams((FilesetEntryKey) key);
RecursiveFilesystemTraversalValue traversalValue =
(RecursiveFilesystemTraversalValue) env.getValue(FilesetTraversalRequest.create(params));
if (traversalValue == null) {
return null;
}
// The root can only be absent for the EMPTY RecursiveFilesystemTraversalValue instance.
if (traversalValue.getResolvedRoot().isEmpty()) {
return FilesetEntryValue.EMPTY;
}
ResolvedFile resolvedRoot = traversalValue.getResolvedRoot().get();
// Handle dangling symlinks gracefully be returning empty results.
if (!resolvedRoot.getType().exists()) {
return FilesetEntryValue.EMPTY;
}
// The "direct" traversal params are present, which is the case when the FilesetEntry
// specifies a package's BUILD file, a directory or a list of files.
// The root of the direct traversal is defined as follows.
//
// If FilesetEntry.files is specified, then a TraversalRequest is created for each entry, the
// root being the respective entry itself. These are all traversed for they may be
// directories or symlinks to directories, and we need to establish Skyframe dependencies on
// their contents for incremental correctness. If an entry is indeed a directory (but not when
// it's a symlink to one) then we have to create symlinks to each of their children.
// (NB: there seems to be no good reason for this, it's just how legacy Fileset works. We may
// want to consider creating a symlink just for the directory and not for its child elements.)
//
// If FilesetEntry.files is not specified, then srcdir refers to either a BUILD file or a
// directory. For the former, the root will be the parent of the BUILD file. For the latter,
// the root will be srcdir itself.
DirectTraversal direct = params.getDirectTraversal();
// The prefix to remove is the entire path of the root. This is OK:
// - when the root is a file, this removes the entire path, but the traversal's destination
// path is actually the name of the output symlink, so this works out correctly
// - when the root is a directory or a symlink to one then we need to strip off the
// directory's path from every result (this is how the output symlinks must be created)
// before making them relative to the destination path
PathFragment prefixToRemove = direct.getRoot().getRelativePart();
Iterable<ResolvedFile> results;
if (direct.isRecursive()
|| (resolvedRoot.getType().isDirectory() && !resolvedRoot.getType().isSymlink())) {
// The traversal is recursive (requested for an entire FilesetEntry.srcdir) or it was
// requested for a FilesetEntry.files entry which turned out to be a directory. We need to
// create an output symlink for every file in it and all of its subdirectories. Only
// exception is when the subdirectory is really a symlink to a directory -- no output
// shall be created for the contents of those.
// Now we create Dir objects to model the filesystem tree. The object employs a trick to
// find directory symlinks: directory symlinks have corresponding ResolvedFile entries and
// are added as files too, while their children, also added as files, contain the path of
// the parent. Finding and discarding the children is easy if we traverse the tree from
// root to leaf.
DirectoryTree root = new DirectoryTree();
for (ResolvedFile f : traversalValue.getTransitiveFiles().toList()) {
PathFragment path = f.getNameInSymlinkTree().relativeTo(prefixToRemove);
if (!path.isEmpty()) {
path = params.getDestPath().getRelative(path);
DirectoryTree dir = root;
for (String segment : path.getParentDirectory().segments()) {
dir = dir.addOrGetSubdir(segment);
}
dir.maybeAddFile(f);
}
}
// Here's where the magic happens. The returned iterable will yield all files in the
// directory that are not under symlinked directories, as well as all directory symlinks.
results = root.iterateFiles();
} else {
// If we're on this branch then the traversal was done for just one entry in
// FilesetEntry.files (which was not a directory, so it was either a file, a symlink to one
// or a symlink to a directory), meaning we'll have only one output symlink.
results = ImmutableList.of(resolvedRoot);
}
// The map of output symlinks. Each key is the path of an output symlink that the Fileset must
// create, relative to the Fileset.out directory, and each value specifies extra information
// about the link (its target, associated metadata, and again its name).
Map<PathFragment, FilesetOutputSymlink> outputSymlinks = new LinkedHashMap<>();
// Create one output symlink for each entry in the results.
for (ResolvedFile f : results) {
// The linkName has to be under the traversal's root, which is also the prefix to remove.
PathFragment linkName = f.getNameInSymlinkTree().relativeTo(prefixToRemove);
// Check whether the symlink is excluded before attempting to resolve it. It may be dangling,
// but excluding it is still fine. Only top-level files can be excluded, i.e. ones that are
// directly under the root if the root is a directory. Matching on getSegment(0) is sufficient
// to satisfy this, since any specified exclusions with multiple segments will never match.
// TODO(b/64754128): Investigate if we could have made the exclude earlier before
// unnecessarily iterating over all the files in an excluded directory.
if (!linkName.isEmpty() && params.getExcludedFiles().contains(linkName.getSegment(0))) {
continue;
}
PathFragment targetName;
try {
targetName = f.getTargetInSymlinkTree(direct.isFollowingSymlinks());
} catch (DanglingSymlinkException e) {
throw new FilesetEntryFunctionException(e);
}
maybeStoreSymlink(
linkName,
targetName,
f.getMetadata(),
params.getDestPath(),
direct.isGenerated(),
outputSymlinks,
getExecRoot.apply(workspaceNameValue.getName()));
}
return FilesetEntryValue.of(ImmutableSet.copyOf(outputSymlinks.values()));
}
/** Stores an output symlink unless it would overwrite an existing one. */
private static void maybeStoreSymlink(
PathFragment linkName,
PathFragment linkTarget,
HasDigest metadata,
PathFragment destPath,
boolean isGenerated,
Map<PathFragment, FilesetOutputSymlink> result,
Path execRoot) {
linkName = destPath.getRelative(linkName);
if (!result.containsKey(linkName)) {
result.put(
linkName,
FilesetOutputSymlink.create(
linkName, linkTarget, metadata, isGenerated, execRoot.asFragment()));
}
}
/**
* Returns the {@link TraversalRequest} node used to compute the Skyframe value for {@code
* filesetEntryKey}. Should only be called to determine which nodes need to be rewound, and only
* when {@code filesetEntryKey.isGenerated()}.
*/
public static TraversalRequest getDependencyForRewinding(FilesetEntryKey key) {
FilesetTraversalParams params = checkParams(key);
checkState(
params.getDirectTraversal().isGenerated(),
"Rewinding is only supported for outputs: %s",
params);
// Traversals in the output tree inline any recursive TraversalRequest evaluations, i.e. there
// won't be any transitively depended-on TraversalRequests.
return FilesetTraversalRequest.create(params);
}
private static FilesetTraversalParams checkParams(FilesetEntryKey key) {
FilesetTraversalParams params = key.argument();
checkState(
params.getDirectTraversal() != null && params.getNestedArtifact() == null,
"FilesetEntry does not support nested traversal: %s",
params);
return params;
}
/**
* Models a FilesetEntryFunction's portion of the symlink output tree created by a Fileset rule.
*
* <p>A Fileset rule's output is computed by zero or more {@link FilesetEntryFunction}s, resulting
* in one {@link FilesetEntryValue} for each. Each of those represents a portion of the grand
* output tree of the Fileset. These portions are later merged and written to the fileset manifest
* file, which is then consumed by a tool that ultimately creates the symlinks in the filesystem.
*
* <p>Because the Fileset doesn't process the lists in the FilesetEntryValues any further than
* merging them, they have to adhere to the conventions of the manifest file. One of these is that
* files are alphabetically ordered (enables the consumer of the manifest to work faster than
* otherwise) and another is that the contents of regular directories are listed, but contents
* of directory symlinks are not, only the symlinks are. (Other details of the manifest file are
* not relevant here.)
*
* <p>See {@link DirectoryTree#iterateFiles()} for more details.
*/
private static final class DirectoryTree {
// Use TreeMaps for the benefit of alphabetically ordered iteration.
public final Map<String, ResolvedFile> files = new TreeMap<>();
public final Map<String, DirectoryTree> dirs = new TreeMap<>();
DirectoryTree addOrGetSubdir(String name) {
DirectoryTree result = dirs.get(name);
if (result == null) {
result = new DirectoryTree();
dirs.put(name, result);
}
return result;
}
void maybeAddFile(ResolvedFile r) {
String name = r.getNameInSymlinkTree().getBaseName();
if (!files.containsKey(name)) {
files.put(name, r);
}
}
/**
* Lazily yields all files in this directory and all of its subdirectories.
*
* <p>The function first yields all the files directly under this directory, in alphabetical
* order. Then come the contents of subdirectories, processed recursively in the same fashion
* as this directory, and also in alphabetical order.
*
* <p>If a directory symlink is encountered its contents are not listed, only the symlink is.
*/
Iterable<ResolvedFile> iterateFiles() {
// 1. Filter directory symlinks. If the symlink target contains files, those were added
// as normal files so their parent directory (the symlink) would show up in the dirs map
// (as a directory) as well as in the files map (as a symlink to a directory).
final Set<String> fileNames = files.keySet();
Iterable<Map.Entry<String, DirectoryTree>> noDirSymlinkes =
Iterables.filter(dirs.entrySet(), input -> !fileNames.contains(input.getKey()));
// 2. Extract the iterables of the true subdirectories.
Iterable<Iterable<ResolvedFile>> subdirIters =
Iterables.transform(noDirSymlinkes, input -> input.getValue().iterateFiles());
// 3. Just concat all subdirectory iterations for one, seamless iteration.
Iterable<ResolvedFile> dirsIter = Iterables.concat(subdirIters);
return Iterables.concat(files.values(), dirsIter);
}
}
}