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, 38 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/vfs/FileSystemUtils.java b/src/main/java/com/google/devtools/build/lib/vfs/FileSystemUtils.java
index adeb9c847c..b7fd8d2a43 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/FileSystemUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/FileSystemUtils.java
@@ -25,7 +25,6 @@ import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.io.PrintStream;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -90,25 +89,13 @@ public class FileSystemUtils {
 
     return a;
   }
-  /**
-   * Returns a path fragment from a given from-dir to a given to-path. May be
-   * either a short relative path "foo/bar", an up'n'over relative path
-   * "../../foo/bar" or an absolute path.
-   */
-  public static PathFragment relativePath(Path fromDir, Path to) {
-    if (to.getFileSystem() != fromDir.getFileSystem()) {
-      throw new IllegalArgumentException("fromDir and to must be on the same FileSystem");
-    }
-
-    return relativePath(fromDir.asFragment(), to.asFragment());
-  }
 
   /**
    * Returns a path fragment from a given from-dir to a given to-path.
    */
   public static PathFragment relativePath(PathFragment fromDir, PathFragment to) {
     if (to.equals(fromDir)) {
-      return PathFragment.create(".");  // same dir, just return '.'
+      return PathFragment.EMPTY_FRAGMENT;
     }
     if (to.startsWith(fromDir)) {
       return to.relativeTo(fromDir);  // easy case--it's a descendant
@@ -883,30 +870,6 @@ public class FileSystemUtils {
   }
 
   /**
-   * Dumps diagnostic information about the specified filesystem to {@code out}.
-   * This is the implementation of the filesystem part of the 'blaze dump'
-   * command. It lives here, rather than in DumpCommand, because it requires
-   * privileged access to members of this package.
-   *
-   * <p>Its results are unspecified and MUST NOT be interpreted programmatically.
-   */
-  public static void dump(FileSystem fs, final PrintStream out) {
-    // Unfortunately there's no "letrec" for anonymous functions so we have to
-    // (a) name the function, (b) put it in a box and (c) use List not array
-    // because of the generic type.  *sigh*.
-    final List<Predicate<Path>> dumpFunction = new ArrayList<>();
-    dumpFunction.add(
-        child -> {
-          Path path = child;
-          out.println("  " + path + " (" + path.toDebugString() + ")");
-          path.applyToChildren(dumpFunction.get(0));
-          return false;
-        });
-
-    fs.getRootDirectory().applyToChildren(dumpFunction.get(0));
-  }
-
-  /**
    * Returns the type of the file system path belongs to.
    */
   public static String getFileSystem(Path path) {