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, 1 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/vfs/PathFragmentSerializationProxy.java b/src/main/java/com/google/devtools/build/lib/vfs/PathFragmentSerializationProxy.java
index 39aefd1318..4ba66be7fc 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/PathFragmentSerializationProxy.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/PathFragmentSerializationProxy.java
@@ -17,7 +17,6 @@ import java.io.Externalizable;
 import java.io.IOException;
 import java.io.ObjectOutput;
 
-
 /**
  * A helper proxy for serializing immutable {@link PathFragment} objects.
  */
@@ -44,7 +43,7 @@ public final class PathFragmentSerializationProxy implements Externalizable {
   }
 
   private Object readResolve() {
-    return PathFragment.create(pathFragmentString);
+    return PathFragment.createAlreadyNormalized(pathFragmentString);
   }
 }