Add file extension property to Skylark

RELNOTES[NEW]: Files now have an "extension" property in Skylark.

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MOS_MIGRATED_REVID=136425934

1 files changed, 14 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
index 2980e2941d..c6a6ad601a 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
@@ -512,6 +512,20 @@ public final class PathFragment implements Comparable<PathFragment>, Serializabl
   }
 
   /**
+   * Returns the file extension of this path, excluding the period, or "" if there is no extension.
+   */
+  public String getFileExtension() {
+    String baseName = getBaseName();
+
+    int lastIndex = baseName.lastIndexOf('.');
+    if (lastIndex != -1) {
+      return baseName.substring(lastIndex + 1);
+    }
+
+    return "";
+  }
+
+  /**
    * Returns a relative path fragment to this path, relative to
    * {@code ancestorDirectory}.
    * <p>