Pass in runfiles directory

tools/python/runfiles/runfiles.py

@@ -66,11 +66,22 @@
 from ._runfiles_constants import MAIN_REPOSITORY_RUNFILES_DIRECTORY
 
 def CreateManifestBased(manifest_path):
-  return _Runfiles(_ManifestBased(manifest_path))
+  # Based on
+  # https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/bazel/rules/python/python_stub_template.txt;l=134-144
+  runfiles_dir_path = os.environ.get('RUNFILES_DIR', None)
+  if not runfiles_dir_path:
+    if (manifest_path.endswith('.runfiles_manifest') or
+        manifest_path.endswith('.runfiles/MANIFEST')):
+      runfiles_dir_path = manifest_path[:-9]
+    else:
+      raise ValueError(
+          "failed to find runfiles directory for manifest '%s'" % manifest_path)
+
+  return _Runfiles(_ManifestBased(manifest_path), runfiles_dir_path)
 
 
 def CreateDirectoryBased(runfiles_dir_path):
-  return _Runfiles(_DirectoryBased(runfiles_dir_path))
+  return _Runfiles(_DirectoryBased(runfiles_dir_path), runfiles_dir_path)
 
 
 def Create(env=None):
@@ -109,15 +120,17 @@ def Create(env=None):
   return None
 
 
+_UNC_PREFIX = "\\\\?\\"
+
 class _Runfiles(object):
   """Returns the runtime location of runfiles.
 
   Runfiles are data-dependencies of Bazel-built binaries and tests.
   """
 
-  def __init__(self, strategy):
+  def __init__(self, strategy, runfiles_dir_path):
     self._strategy = strategy
-    self._python_runfiles_root = _FindPythonRunfilesRoot()
+    self._runfiles_dir_path = runfiles_dir_path
 
   def Rlocation(self, path):
     """Returns the runtime path of a runfile.
@@ -198,9 +211,11 @@ def CurrentRepository(self, frame = 1):
       caller_path = inspect.getfile(sys._getframe(frame))
     except ValueError:
       raise ValueError("failed to determine caller's file path")
-    caller_runfiles_path = os.path.relpath(caller_path, self._python_runfiles_root)
+    if caller_path.startswith(_UNC_PREFIX):
+      caller_path = caller_path[len(_UNC_PREFIX):]
+    caller_runfiles_path = os.path.relpath(caller_path, self._runfiles_dir_path)
     if caller_runfiles_path.startswith(".." + os.path.sep):
-      raise ValueError('{} does not lie under the runfiles root {}'.format(caller_path, self._python_runfiles_root))
+      raise ValueError("{} does not lie under the runfiles root {}".format(caller_path, self._runfiles_dir_path))
 
     caller_runfiles_directory = caller_runfiles_path[:caller_runfiles_path.find(os.path.sep)]
     if caller_runfiles_directory == MAIN_REPOSITORY_RUNFILES_DIRECTORY:
@@ -211,16 +226,6 @@ def CurrentRepository(self, frame = 1):
     # canonical name.
     return caller_runfiles_directory
 
-def _FindPythonRunfilesRoot():
-  root = __file__
-  # Walk up our own runfiles path to the root of the runfiles tree from which
-  # the current file is being run. This path coincides with what the Bazel
-  # Python stub sets up as sys.path[0]. Since that entry can be changed at
-  # runtime, we rederive it here.
-  for _ in range("bazel_tools/tools/python/runfiles/runfiles.py".count("/") + 1):
-    root = os.path.dirname(root)
-  return root
-
 
 class _ManifestBased(object):
   """`Runfiles` strategy that parses a runfiles-manifest to look up runfiles."""