Windows, Android BusyBox: create JunctionCreator

Introduce the JunctionCreator classes that the
Android BusyBox can use to work around path length
limitations on Windows.

See https://github.com/bazelbuild/bazel/issues/3264

Change-Id: Ia5ee39f0635dcc2690ffb1755dc56d21e7bc7536
PiperOrigin-RevId: 161378422

5 files changed, 206 insertions, 0 deletions

diff --git a/src/tools/android/java/com/google/devtools/build/android/BUILD b/src/tools/android/java/com/google/devtools/build/android/BUILD
index d3bc605e3e..5f1de9dbc3 100644
--- a/src/tools/android/java/com/google/devtools/build/android/BUILD
+++ b/src/tools/android/java/com/google/devtools/build/android/BUILD
@@ -9,6 +9,7 @@ filegroup(
         "classes_deploy.jar",
         "//src/tools/android/java/com/google/devtools/build/android/desugar:embedded_tools",
         "//src/tools/android/java/com/google/devtools/build/android/incrementaldeployment:embedded_tools",
+        "//src/tools/android/java/com/google/devtools/build/android/junctions:embedded_tools",
         "//src/tools/android/java/com/google/devtools/build/android/proto:srcs",
     ],
 )
@@ -38,6 +39,7 @@ java_library(
         "//src/main/java/com/google/devtools/common/options",
         "//src/main/protobuf:option_filters_java_proto",
         "//src/main/protobuf:package_manifest_java_proto",
+        "//src/tools/android/java/com/google/devtools/build/android/junctions",
         "//src/tools/android/java/com/google/devtools/build/android/proto:serialize_format_java_pb",
         "//src/tools/android/java/com/google/devtools/build/android/resources",
         "//third_party:android_common_25_0_0",
@@ -58,6 +60,7 @@ filegroup(
         "//src/tools/android/java/com/google/devtools/build/android/ideinfo:srcs",
         "//src/tools/android/java/com/google/devtools/build/android/idlclass:srcs",
         "//src/tools/android/java/com/google/devtools/build/android/incrementaldeployment:srcs",
+        "//src/tools/android/java/com/google/devtools/build/android/junctions:srcs",
         "//src/tools/android/java/com/google/devtools/build/android/proto:srcs",
         "//src/tools/android/java/com/google/devtools/build/android/resources:srcs",
         "//src/tools/android/java/com/google/devtools/build/android/ziputils:srcs",
diff --git a/src/tools/android/java/com/google/devtools/build/android/junctions/BUILD b/src/tools/android/java/com/google/devtools/build/android/junctions/BUILD
new file mode 100644
index 0000000000..d54aecd406
--- /dev/null
+++ b/src/tools/android/java/com/google/devtools/build/android/junctions/BUILD
@@ -0,0 +1,47 @@
+package(default_visibility = ["//visibility:private"])
+
+package_group(
+    name = "android-prod",
+    packages = [
+        "//src/tools/android/java/com/google/devtools/build/android",
+    ],
+)
+
+package_group(
+    name = "android-tests",
+    packages = [
+        "//src/test/java/com/google/devtools/build/android/...",
+    ],
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+    visibility = [":android-prod"],
+)
+
+filegroup(
+    name = "embedded_tools",
+    srcs = glob(["*.java"]),
+    visibility = [":android-prod"],
+)
+
+java_library(
+    name = "junctions",
+    srcs = glob(["*.java"]),
+    data = select({
+        "//src:windows": ["//src/main/native/windows:windows_jni"],
+        "//src:windows_msvc": ["//src/main/native/windows:windows_jni"],
+        "//src:windows_msys": ["//src/main/native/windows:windows_jni"],
+        "//conditions:default": [],
+    }),
+    visibility = [
+        ":android-prod",
+        ":android-tests",
+    ],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib/windows/jni:file",
+        "//third_party:guava",
+        "//third_party:jsr305",
+    ],
+)
diff --git a/src/tools/android/java/com/google/devtools/build/android/junctions/JunctionCreator.java b/src/tools/android/java/com/google/devtools/build/android/junctions/JunctionCreator.java
new file mode 100644
index 0000000000..fe82e34180
--- /dev/null
+++ b/src/tools/android/java/com/google/devtools/build/android/junctions/JunctionCreator.java
@@ -0,0 +1,46 @@
+// Copyright 2017 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.android.junctions;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.nio.file.Path;
+import javax.annotation.Nullable;
+
+/**
+ * Interface to create junctions (directory symlinks).
+ *
+ * <p>Junctions are directory symlinks on NTFS filesystems. They are useful on Windows, because
+ * creating them doesn't require any privileges, as opposed to the creation of file symlinks which
+ * does.
+ *
+ * <p>On Windows, Bazel and the Android BusyBox uses junctions to work around path length
+ * limitations of the Windows Shell and of tools like aapt.exe and the PNG cruncher. The limit is
+ * 260 characters for all paths. The filesystem supports longer paths than that, but the tools
+ * usually don't. To work around that limitation, we create junctions that have short paths but
+ * point to long paths (this is allowed).
+ *
+ * <p>On Linux/MacOS the junction creator may have a no-op implementation.
+ */
+public interface JunctionCreator extends Closeable {
+  /**
+   * Returns an equivalent path to `target`, which may or may not be the same as `target`.
+   *
+   * <p>Depending on the implementation, this method may return `target` itself, or may create a
+   * junction that points to `target` (if `target` is a directory) or the parent of it (if `target`
+   * is a file).
+   */
+  @Nullable
+  public abstract Path create(@Nullable Path target) throws IOException;
+}
diff --git a/src/tools/android/java/com/google/devtools/build/android/junctions/NoopJunctionCreator.java b/src/tools/android/java/com/google/devtools/build/android/junctions/NoopJunctionCreator.java
new file mode 100644
index 0000000000..5b061f3fbd
--- /dev/null
+++ b/src/tools/android/java/com/google/devtools/build/android/junctions/NoopJunctionCreator.java
@@ -0,0 +1,30 @@
+// Copyright 2017 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.android.junctions;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import javax.annotation.Nullable;
+
+/** A no-op JunctionCreator implementation that just returns the input path. */
+public final class NoopJunctionCreator implements JunctionCreator {
+  @Nullable
+  @Override
+  public Path create(@Nullable Path path) throws IOException {
+    return path;
+  }
+
+  @Override
+  public void close() throws IOException {}
+}
diff --git a/src/tools/android/java/com/google/devtools/build/android/junctions/WindowsJunctionCreator.java b/src/tools/android/java/com/google/devtools/build/android/junctions/WindowsJunctionCreator.java
new file mode 100644
index 0000000000..278b55d34c
--- /dev/null
+++ b/src/tools/android/java/com/google/devtools/build/android/junctions/WindowsJunctionCreator.java
@@ -0,0 +1,80 @@
+// Copyright 2017 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.android.junctions;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.windows.jni.WindowsFileOperations;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * Junction creator implementation for Windows.
+ *
+ * <p>Creates a junction (or uses a cached one) for a path. If the path is a directory, the junction
+ * points to it, and the returned path is the junction's path. If the path is a file, the junction
+ * points to its parent, and the returned path is the file's path through the junction.
+ *
+ * <p>The `close` method deletes all junctions that this object created, along with the `dir`
+ * directory where the junctions are created. The purpose of this is to avoid other methods (such as
+ * ScopedTemporaryDirectory.close) to traverse these junctions believing they are regular
+ * directories and deleting files in them that are actually outside of the directory tree.
+ */
+public final class WindowsJunctionCreator implements JunctionCreator {
+  private final Path dir;
+  private Map<Path, Path> paths; // allocated lazily, but semantically final
+  private int junctionIndex = 0;
+
+  public WindowsJunctionCreator(Path dir) {
+    this.dir = Preconditions.checkNotNull(dir);
+  }
+
+  @Nullable
+  public Path create(@Nullable Path path) throws IOException {
+    if (path == null) {
+      return null;
+    }
+
+    if (paths == null) {
+      paths = new HashMap<>();
+    }
+    path = path.toAbsolutePath();
+    if (path.toFile().isDirectory()) {
+      Path link = paths.get(path);
+      if (link == null) {
+        link = dir.resolve(Integer.toString(junctionIndex++));
+        WindowsFileOperations.createJunction(link.toString(), path.toString());
+        paths.put(path, link);
+      }
+      return link;
+    }
+
+    Path parent = path.getParent();
+    return (parent == null) ? path : create(parent).resolve(path.getFileName());
+  }
+
+  @Override
+  public void close() throws IOException {
+    // Delete all junctions, otherwise the temp directory deleter would follow them and delete files
+    // from directories they point to.
+    if (paths != null) {
+      for (Path link : paths.values()) {
+        link.toFile().delete();
+      }
+    }
+    dir.toFile().delete();
+  }
+}