Java tutorial
// 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 com.google.common.base.Function; import com.google.common.base.Predicate; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableSet; import com.google.common.collect.Iterables; import com.google.common.collect.Sets; 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.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.util.Preconditions; 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.Map.Entry; import java.util.Set; import java.util.TreeMap; /** SkyFunction for {@link FilesetEntryValue}. */ public final class FilesetEntryFunction implements SkyFunction { private static final class MissingDepException extends Exception { } private static final class FilesetEntryFunctionException extends SkyFunctionException { FilesetEntryFunctionException(RecursiveFilesystemTraversalException e) { super(e, Transience.PERSISTENT); } } @Override public SkyValue compute(SkyKey key, Environment env) throws FilesetEntryFunctionException, InterruptedException { FilesetTraversalParams t = (FilesetTraversalParams) key.argument(); Preconditions.checkState(t.getNestedTraversal().isPresent() != t.getDirectTraversal().isPresent(), "Exactly one of the nested and direct traversals must be specified: %s", t); // Create the set of excluded files. Only top-level files can be excluded, i.e. ones that are // directly under the root if the root is a directory. Set<String> exclusions = createExclusionSet(t.getExcludedFiles()); // The map of output symlinks. Each key is the path of a 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<>(); if (t.getNestedTraversal().isPresent()) { // The "nested" traversal parameters are present if and only if FilesetEntry.srcdir specifies // another Fileset (a "nested" one). FilesetEntryValue nested = (FilesetEntryValue) env .getValue(FilesetEntryValue.key(t.getNestedTraversal().get())); if (env.valuesMissing()) { return null; } for (FilesetOutputSymlink s : nested.getSymlinks()) { if (!exclusions.contains(s.name.getPathString())) { maybeStoreSymlink(s, t.getDestPath(), outputSymlinks); } } } else { // The "nested" traversal params are absent if and only if 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 childen. // (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 = t.getDirectTraversal().get(); RecursiveFilesystemTraversalValue rftv; try { // Traverse the filesystem to establish skyframe dependencies. rftv = traverse(env, createErrorInfo(t), direct); } catch (MissingDepException e) { return null; } // The root can only be absent for the EMPTY rftv instance. if (!rftv.getResolvedRoot().isPresent()) { return FilesetEntryValue.EMPTY; } ResolvedFile resolvedRoot = rftv.getResolvedRoot().get(); // Handle dangling symlinks gracefully be returning empty results. if (!resolvedRoot.getType().exists()) { return FilesetEntryValue.EMPTY; } // 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 = null; 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 : rftv.getTransitiveFiles().toCollection()) { PathFragment path = f.getNameInSymlinkTree().relativeTo(prefixToRemove); if (path.segmentCount() > 0) { path = t.getDestPath().getRelative(path); DirectoryTree dir = root; for (int i = 0; i < path.segmentCount() - 1; ++i) { dir = dir.addOrGetSubdir(path.getSegment(i)); } 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); } // 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. if (exclusions.contains(linkName.getPathString())) { continue; } PathFragment targetName; try { targetName = f.getTargetInSymlinkTree(direct.isFollowingSymlinks()); } catch (DanglingSymlinkException e) { throw new FilesetEntryFunctionException(e); } // Metadata field must be present. It can only be absent when stripped by tests. String metadata = Integer.toHexString(f.getMetadataHash()); maybeStoreSymlink(linkName, targetName, metadata, t.getDestPath(), outputSymlinks); } } return FilesetEntryValue.of(ImmutableSet.copyOf(outputSymlinks.values())); } /** Stores an output symlink unless it would overwrite an existing one. */ private static void maybeStoreSymlink(FilesetOutputSymlink nestedLink, PathFragment destPath, Map<PathFragment, FilesetOutputSymlink> result) { maybeStoreSymlink(nestedLink.name, nestedLink.target, nestedLink.metadata, destPath, result); } /** Stores an output symlink unless it would overwrite an existing one. */ private static void maybeStoreSymlink(PathFragment linkName, PathFragment linkTarget, String metadata, PathFragment destPath, Map<PathFragment, FilesetOutputSymlink> result) { linkName = destPath.getRelative(linkName); if (!result.containsKey(linkName)) { result.put(linkName, new FilesetOutputSymlink(linkName, linkTarget, metadata)); } } private static Set<String> createExclusionSet(Set<String> input) { return Sets.filter(input, new Predicate<String>() { @Override public boolean apply(String e) { // Keep the top-level exclusions only. Do not look for "/" but count the path segments // instead, in anticipation of future Windows support. return new PathFragment(e).segmentCount() == 1; } }); } @Override public String extractTag(SkyKey skyKey) { return null; } private static RecursiveFilesystemTraversalValue traverse(Environment env, String errorInfo, DirectTraversal traversal) throws MissingDepException, InterruptedException { SkyKey depKey = RecursiveFilesystemTraversalValue .key(new RecursiveFilesystemTraversalValue.TraversalRequest(traversal.getRoot().asRootedPath(), traversal.isGenerated(), traversal.getPackageBoundaryMode(), traversal.isPackage(), errorInfo, /*pattern=*/null)); RecursiveFilesystemTraversalValue v = (RecursiveFilesystemTraversalValue) env.getValue(depKey); if (env.valuesMissing()) { throw new MissingDepException(); } return v; } private static String createErrorInfo(FilesetTraversalParams t) { if (t.getDirectTraversal().isPresent()) { DirectTraversal direct = t.getDirectTraversal().get(); return String.format("Fileset '%s' traversing %s '%s'", t.getOwnerLabelForErrorMessages(), direct.isPackage() ? "package" : "file (or directory)", direct.getRoot().getRelativePart().getPathString()); } else { return String.format("Fileset '%s' traversing another Fileset", t.getOwnerLabelForErrorMessages()); } } /** * 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(), new Predicate<Map.Entry<String, DirectoryTree>>() { @Override public boolean apply(Map.Entry<String, DirectoryTree> input) { return !fileNames.contains(input.getKey()); } }); // 2. Extract the iterables of the true subdirectories. Iterable<Iterable<ResolvedFile>> subdirIters = Iterables.transform(noDirSymlinkes, new Function<Map.Entry<String, DirectoryTree>, Iterable<ResolvedFile>>() { @Override public Iterable<ResolvedFile> apply(Entry<String, DirectoryTree> input) { return 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); } } }