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, 2 insertions, 3 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
index 783899ab45..f54522f8f1 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/TreeArtifactValue.java
@@ -182,8 +182,7 @@ class TreeArtifactValue implements SkyValue {
       PathFragment pathToExplode, ImmutableSet.Builder<PathFragment> valuesBuilder)
       throws IOException {
     for (Path subpath : treeArtifact.getPath().getRelative(pathToExplode).getDirectoryEntries()) {
-      PathFragment canonicalSubpathFragment =
-          pathToExplode.getChild(subpath.getBaseName()).normalize();
+      PathFragment canonicalSubpathFragment = pathToExplode.getChild(subpath.getBaseName());
       if (subpath.isDirectory()) {
         explodeDirectory(treeArtifact,
             pathToExplode.getChild(subpath.getBaseName()), valuesBuilder);
@@ -202,7 +201,7 @@ class TreeArtifactValue implements SkyValue {
         // TreeArtifact into a/b/outside_dir.
         PathFragment intermediatePath = canonicalSubpathFragment.getParentDirectory();
         for (String pathSegment : linkTarget.getSegments()) {
-          intermediatePath = intermediatePath.getRelative(pathSegment).normalize();
+          intermediatePath = intermediatePath.getRelative(pathSegment);
           if (intermediatePath.containsUplevelReferences()) {
             String errorMessage = String.format(
                 "A TreeArtifact may not contain relative symlinks whose target paths traverse "