Replace path implementation.

Path and PathFragment have been replaced with String-based implementations. They are pretty similar, but each method is dissimilar enough that I did not feel sharing code was appropriate.

A summary of changes:

PATH
====

* Subsumes LocalPath (deleted, its tests repurposed)
* Use a simple string to back Path
* Path instances are no longer interned; Reference equality will no longer work
* Always normalized (same as before)
* Some operations will now be slower, like instance compares (which were previously just a reference check)
* Multiple identical paths will now consume more memory since they are not interned

PATH FRAGMENT
=============

* Use a simple string to back PathFragment
* No more segment arrays with interned strings
* Always normalized
* Remove isNormalized
* Replace some isNormalizied uses with containsUpLevelReferences() to check if path fragments try to escape their scope
* To check if user input is normalized, supply static methods on PathFragment to validate the string before constructing a PathFragment
* Because PathFragments are always normalized, we have to replace checks for literal "." from PathFragment#getPathString to PathFragment#getSafePathString. The latter returns "." for the empty string.
* The previous implementation supported efficient segment semantics (segment count, iterating over segments). This is now expensive since we do longer have a segment array.

ARTIFACT
========

* Remove Path instance. It is instead dynamically constructed on request. This is necessary to avoid this CL becoming a memory regression.

RELNOTES: None
PiperOrigin-RevId: 185062932

1 files changed, 141 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java b/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java
new file mode 100644
index 0000000000..7494683391
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/vfs/PathAbstractTest.java
@@ -0,0 +1,141 @@
+// 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.lib.vfs;
+
+import static com.google.common.truth.Truth.assertThat;
+import static java.util.stream.Collectors.toList;
+
+import com.google.common.collect.Lists;
+import com.google.common.testing.EqualsTester;
+import com.google.devtools.build.lib.clock.BlazeClock;
+import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.util.Collections;
+import java.util.List;
+import org.junit.Before;
+import org.junit.Test;
+
+/** Tests for {@link Path}. */
+public abstract class PathAbstractTest {
+
+  private FileSystem fileSystem;
+  private boolean isCaseSensitive;
+
+  @Before
+  public void setup() {
+    fileSystem = new InMemoryFileSystem(BlazeClock.instance());
+    isCaseSensitive = OsPathPolicy.getFilePathOs().isCaseSensitive();
+  }
+
+  @Test
+  public void testStripsTrailingSlash() {
+    // compare string forms
+    assertThat(create("/foo/bar/").getPathString()).isEqualTo("/foo/bar");
+    // compare fragment forms
+    assertThat(create("/foo/bar/")).isEqualTo(create("/foo/bar"));
+  }
+
+  @Test
+  public void testBasename() throws Exception {
+    assertThat(create("/foo/bar").getBaseName()).isEqualTo("bar");
+    assertThat(create("/foo/").getBaseName()).isEqualTo("foo");
+    assertThat(create("/foo").getBaseName()).isEqualTo("foo");
+    assertThat(create("/").getBaseName()).isEmpty();
+  }
+
+  @Test
+  public void testNormalStringsDoNotAllocate() {
+    String normal1 = "/a/b/hello.txt";
+    assertThat(create(normal1).getPathString()).isSameAs(normal1);
+
+    // Sanity check our testing strategy
+    String notNormal = "/a/../b";
+    assertThat(create(notNormal).getPathString()).isNotSameAs(notNormal);
+  }
+
+  @Test
+  public void testComparableSortOrder() {
+    List<Path> list =
+        Lists.newArrayList(
+            create("/zzz"),
+            create("/ZZZ"),
+            create("/ABC"),
+            create("/aBc"),
+            create("/AbC"),
+            create("/abc"));
+    Collections.sort(list);
+    List<String> result = list.stream().map(Path::getPathString).collect(toList());
+
+    if (isCaseSensitive) {
+      assertThat(result).containsExactly("/ABC", "/AbC", "/ZZZ", "/aBc", "/abc", "/zzz").inOrder();
+    } else {
+      // Partial ordering among case-insensitive items guaranteed by Collections.sort stability
+      assertThat(result).containsExactly("/ABC", "/aBc", "/AbC", "/abc", "/zzz", "/ZZZ").inOrder();
+    }
+  }
+
+  @Test
+  public void testSerialization() throws Exception {
+    FileSystem oldFileSystem = Path.getFileSystemForSerialization();
+    try {
+      Path.setFileSystemForSerialization(fileSystem);
+      Path root = fileSystem.getPath("/");
+      Path p1 = fileSystem.getPath("/foo");
+      Path p2 = fileSystem.getPath("/foo/bar");
+
+      ByteArrayOutputStream bos = new ByteArrayOutputStream();
+      ObjectOutputStream oos = new ObjectOutputStream(bos);
+
+      oos.writeObject(root);
+      oos.writeObject(p1);
+      oos.writeObject(p2);
+
+      ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
+      ObjectInputStream ois = new ObjectInputStream(bis);
+
+      Path dsRoot = (Path) ois.readObject();
+      Path dsP1 = (Path) ois.readObject();
+      Path dsP2 = (Path) ois.readObject();
+
+      new EqualsTester()
+          .addEqualityGroup(root, dsRoot)
+          .addEqualityGroup(p1, dsP1)
+          .addEqualityGroup(p2, dsP2)
+          .testEquals();
+
+      assertThat(p2.startsWith(p1)).isTrue();
+      assertThat(p2.startsWith(dsP1)).isTrue();
+      assertThat(dsP2.startsWith(p1)).isTrue();
+      assertThat(dsP2.startsWith(dsP1)).isTrue();
+
+      // Regression test for a very specific bug in compareTo involving our incorrect usage of
+      // reference equality rather than logical equality.
+      String relativePathStringA = "child/grandchildA";
+      String relativePathStringB = "child/grandchildB";
+      assertThat(
+              p1.getRelative(relativePathStringA).compareTo(dsP1.getRelative(relativePathStringB)))
+          .isEqualTo(
+              p1.getRelative(relativePathStringA).compareTo(p1.getRelative(relativePathStringB)));
+    } finally {
+      Path.setFileSystemForSerialization(oldFileSystem);
+    }
+  }
+
+  protected Path create(String path) {
+    return Path.create(path, fileSystem);
+  }
+}