--watchfs for OSX: use kFSEventStreamCreateFlagNoDefer to receive event as soon as they arrives

See https://developer.apple.com/reference/coreservices/1455376-fseventstreamcreateflags/kfseventstreamcreateflagnodefer?language=objc

Also added the integration test now it is no more flaky.
Tested with `bazel test src/test/java/com/google/devtools/build/lib/skyframe:SkyframeTests --runs_per_test 10 --test_filter=com.google.devtools.build.lib.skyframe.MacOSXFsEventsDiffAwarenessTest --nocache_test_results`

Fixes #1362.

--
Change-Id: I42ceebd8c5a2e0156653b140ca049af45d2e1e80
Reviewed-on: https://bazel-review.googlesource.com/6613
MOS_MIGRATED_REVID=136078777

src/test/java/com/google/devtools/build/lib/skyframe/BUILD

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/BUILD b/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
index 04438e1..ff94116 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
@@ -41,9 +41,14 @@
 
 java_test(
     name = "SkyframeTests",
-    srcs = glob([
-        "*.java",
-    ]),
+    srcs = select({
+        "//src:darwin": glob(["*.java"]),
+        "//src:darwin_x86_64": glob(["*.java"]),
+        "//conditions:default": glob(
+            ["*.java"],
+            exclude = ["MacOSXFsEventsDiffAwarenessTest.java"],
+        ),
+    }),
     tags = ["skyframe"],
     test_class = "com.google.devtools.build.lib.AllTests",
     deps = [

src/test/java/com/google/devtools/build/lib/skyframe/MacOSXFsEventsDiffAwarenessTest.java

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/MacOSXFsEventsDiffAwarenessTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/MacOSXFsEventsDiffAwarenessTest.java
new file mode 100644
index 0000000..490c002
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/MacOSXFsEventsDiffAwarenessTest.java
@@ -0,0 +1,115 @@
+// Copyright 2016 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.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.devtools.build.lib.skyframe.DiffAwareness.View;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link MacOSXFsEventsDiffAwareness} */
+@RunWith(JUnit4.class)
+public class MacOSXFsEventsDiffAwarenessTest {
+
+  private static void rmdirs(Path directory) throws IOException {
+    Files.walkFileTree(
+        directory,
+        new SimpleFileVisitor<Path>() {
+          @Override
+          public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
+              throws IOException {
+            Files.delete(file);
+            return FileVisitResult.CONTINUE;
+          }
+
+          @Override
+          public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+            Files.delete(dir);
+            return FileVisitResult.CONTINUE;
+          }
+        });
+  }
+
+  private MacOSXFsEventsDiffAwareness underTest;
+  private Path watchedPath;
+
+  @Before
+  public void setUp() throws Exception {
+    watchedPath = com.google.common.io.Files.createTempDir().getCanonicalFile().toPath();
+    underTest = new MacOSXFsEventsDiffAwareness(watchedPath.toString());
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    underTest.close();
+    rmdirs(watchedPath);
+  }
+
+  private void scratchFile(String path, String content) throws IOException {
+    Path p = watchedPath.resolve(path);
+    p.getParent().toFile().mkdirs();
+    com.google.common.io.Files.write(content.getBytes(StandardCharsets.UTF_8), p.toFile());
+  }
+
+  private void scratchFile(String path) throws IOException {
+    scratchFile(path, "");
+  }
+
+  private void assertDiff(View view1, View view2, Object... paths)
+      throws IncompatibleViewException, BrokenDiffAwarenessException {
+    ImmutableSet<PathFragment> modifiedSourceFiles =
+        underTest.getDiff(view1, view2).modifiedSourceFiles();
+    ImmutableSet<String> toStringSourceFiles = toString(modifiedSourceFiles);
+    assertThat(toStringSourceFiles).containsExactly(paths);
+  }
+
+  private static ImmutableSet<String> toString(ImmutableSet<PathFragment> modifiedSourceFiles) {
+    ImmutableSet.Builder<String> builder = ImmutableSet.builder();
+    for (PathFragment path : modifiedSourceFiles) {
+      if (!path.toString().isEmpty()) {
+        builder.add(path.toString());
+      }
+    }
+    return builder.build();
+  }
+
+  @Test
+  public void testSimple() throws Exception {
+    View view1 = underTest.getCurrentView();
+    scratchFile("a/b/c");
+    scratchFile("b/c/d");
+    Thread.sleep(200); // Wait until the events propagate
+    View view2 = underTest.getCurrentView();
+    assertDiff(view1, view2, "a", "a/b", "a/b/c", "b", "b/c", "b/c/d");
+    rmdirs(watchedPath.resolve("a"));
+    rmdirs(watchedPath.resolve("b"));
+    Thread.sleep(200); // Wait until the events propagate
+    View view3 = underTest.getCurrentView();
+    assertDiff(view2, view3, "a", "a/b", "a/b/c", "b", "b/c", "b/c/d");
+  }
+}