Sort entries by segment when building a parent node to prevent unorde…

…red directory structures.

When building a parent node from action inputs, the paths to the files are
sorted. These paths are then broken down into segments and a tree structure
is created from the segments.

Problem is, the segments at each level of the tree structure are not sorted
before they are added to the parent node. This can result in an unordered
directory tree.

For example, the sort order of this list of files
/foo/bar-client/bar-client_ijar.jar
/foo/bar/bar_ijar.jar

is maintained when it becomes a tree structure
foo ->
    bar-client ->
        bar-client_ijar.jar
    bar
        bar_ijar.jar

which is out of order.

Resolves: bazelbuild#5109

src/main/java/com/google/devtools/build/lib/remote/TreeNodeRepository.java

@@ -42,6 +42,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
@@ -123,6 +124,8 @@ public boolean equals(Object o) {
       public int hashCode() {
         return Objects.hash(segment, child);
       }
+
+      public static Comparator<ChildEntry> segmentOrder = Comparator.comparing(ChildEntry::getSegment);
     }
 
     // Should only be called by the TreeNodeRepository.
@@ -344,6 +347,7 @@ private TreeNode buildParentNode(
         }
       }
     }
+    Collections.sort(entries, TreeNode.ChildEntry.segmentOrder);
     return interner.intern(new TreeNode(entries, null));
   }
 

src/test/java/com/google/devtools/build/lib/remote/TreeNodeRepositoryTest.java

@@ -151,13 +151,20 @@ public void testDirectoryInput() throws Exception {
     ActionInput fooH = ActionInputHelper.fromPath("/exec/root/a/foo/foo.h");
     scratch.file("/exec/root/a/foo/foo.cc", "2");
     ActionInput fooCc = ActionInputHelper.fromPath("/exec/root/a/foo/foo.cc");
+
     Artifact bar = new Artifact(scratch.file("/exec/root/a/bar.txt"), rootDir);
     TreeNodeRepository repo = createTestTreeNodeRepository();
 
-    TreeNode root = buildFromActionInputs(repo, foo, bar);
+    Artifact aClient = new Artifact(scratch.dir("/exec/root/a-client"), rootDir);
+    scratch.file("/exec/root/a-client/baz.txt", "3");
+    ActionInput baz = ActionInputHelper.fromPath("/exec/root/a-client/baz.txt");
+
+    TreeNode root = buildFromActionInputs(repo, foo, aClient, bar);
     TreeNode aNode = root.getChildEntries().get(0).getChild();
     TreeNode fooNode = aNode.getChildEntries().get(1).getChild(); // foo > bar in sort order!
     TreeNode barNode = aNode.getChildEntries().get(0).getChild();
+    TreeNode aClientNode = root.getChildEntries().get(1).getChild(); // a-client > a in sort order
+    TreeNode bazNode = aClientNode.getChildEntries().get(0).getChild();
 
     TreeNode fooHNode =
         fooNode.getChildEntries().get(1).getChild(); // foo.h > foo.cc in sort order!
@@ -170,18 +177,30 @@ public void testDirectoryInput() throws Exception {
     Digest fooDigest = repo.getMerkleDigest(fooNode);
     Digest fooHDigest = repo.getMerkleDigest(fooHNode);
     Digest fooCcDigest = repo.getMerkleDigest(fooCcNode);
+    Digest aClientDigest = repo.getMerkleDigest(aClientNode);
+    Digest bazDigest = repo.getMerkleDigest(bazNode);
     Digest barDigest = repo.getMerkleDigest(barNode);
     assertThat(digests)
-        .containsExactly(rootDigest, aDigest, barDigest, fooDigest, fooHDigest, fooCcDigest);
+        .containsExactly(
+          rootDigest,
+          aDigest,
+          barDigest,
+          fooDigest,
+          fooCcDigest,
+          fooHDigest,
+          aClientDigest,
+          bazDigest);
 
     ArrayList<Directory> directories = new ArrayList<>();
     ArrayList<ActionInput> actionInputs = new ArrayList<>();
     repo.getDataFromDigests(digests, actionInputs, directories);
-    assertThat(actionInputs).containsExactly(bar, fooH, fooCc);
-    assertThat(directories).hasSize(3); // root, root/a and root/a/foo
+    assertThat(actionInputs).containsExactly(bar, fooH, fooCc, baz);
+    assertThat(directories).hasSize(4); // root, root/a, root/a/foo, and root/a-client
     Directory rootDirectory = directories.get(0);
     assertThat(rootDirectory.getDirectories(0).getName()).isEqualTo("a");
     assertThat(rootDirectory.getDirectories(0).getDigest()).isEqualTo(aDigest);
+    assertThat(rootDirectory.getDirectories(1).getName()).isEqualTo("a-client");
+    assertThat(rootDirectory.getDirectories(1).getDigest()).isEqualTo(aClientDigest);
     Directory aDirectory = directories.get(1);
     assertThat(aDirectory.getFiles(0).getName()).isEqualTo("bar.txt");
     assertThat(aDirectory.getFiles(0).getDigest()).isEqualTo(barDigest);
@@ -192,5 +211,8 @@ public void testDirectoryInput() throws Exception {
     assertThat(fooDirectory.getFiles(0).getDigest()).isEqualTo(fooCcDigest);
     assertThat(fooDirectory.getFiles(1).getName()).isEqualTo("foo.h");
     assertThat(fooDirectory.getFiles(1).getDigest()).isEqualTo(fooHDigest);
+    Directory aClientDirectory = directories.get(3);
+    assertThat(aClientDirectory.getFiles(0).getName()).isEqualTo("baz.txt");
+    assertThat(aClientDirectory.getFiles(0).getDigest()).isEqualTo(bazDigest);
   }
 }