make relative path computation between two runfiles-root relative paths instead of main-repo-root relative paths

Author: rickeylev

python/private/py_executable_bazel.bzl

@@ -323,7 +323,7 @@ def _create_executable(
 
 def _create_zip_main(ctx, *, stage2_bootstrap, runtime_details, venv):
     python_binary = _runfiles_root_path(ctx, venv.interpreter.short_path)
-    python_binary_actual = _runfiles_root_path(ctx, venv.interpreter_actual_path)
+    python_binary_actual = venv.interpreter_actual_path
 
     # The location of this file doesn't really matter. It's added to
     # the zip file as the top-level __main__.py file and not included
@@ -344,7 +344,6 @@ def _create_zip_main(ctx, *, stage2_bootstrap, runtime_details, venv):
     )
     return output
 
-
 # Return a relative path from one path to another, where both paths are each
 # relative paths from a common root.
 def relative_path(from_, to):
@@ -366,8 +365,7 @@ def relative_path(from_, to):
         fail("cannot compute relative path from '%s' to '%s'", from_, to)
 
     parts = ([".."] * len(from_parts)) + to_parts
-    return "/".join(parts)
-
+    return paths.join(*parts)
 
 # Create a venv the executable can use.
 # For venv details and the venv startup process, see:
@@ -393,9 +391,15 @@ def _create_venv(ctx, output_prefix, imports, runtime_details):
         # in runfiles is always a symlink. An RBE implementation, for example,
         # may choose to write what symlink() points to instead.
         interpreter = ctx.actions.declare_symlink("{}/bin/{}".format(venv, py_exe_basename))
-        interpreter_actual_path = runtime.interpreter.short_path
-        venv_bin_dir = paths.dirname(interpreter.short_path)
-        rel_path = relative_path(from_=venv_bin_dir, to=interpreter_actual_path)
+
+        interpreter_actual_path = _runfiles_root_path(ctx, runtime.interpreter.short_path)
+        rel_path = relative_path(
+            # dirname is necessary because a relative symlink is relative to
+            # the directory the symlink resides within.
+            from_ = paths.dirname(_runfiles_root_path(ctx, interpreter.short_path)),
+            to = interpreter_actual_path,
+        )
+
         ctx.actions.symlink(output = interpreter, target_path = rel_path)
     else:
         py_exe_basename = paths.basename(runtime.interpreter_path)
@@ -437,7 +441,7 @@ def _create_venv(ctx, output_prefix, imports, runtime_details):
 
     return struct(
         interpreter = interpreter,
-        # Runfiles-relative path or absolute path
+        # Runfiles root relative path or absolute path
         interpreter_actual_path = interpreter_actual_path,
         files_without_interpreter = [pyvenv_cfg, pth, site_init],
     )
@@ -487,12 +491,22 @@ def _create_stage2_bootstrap(
     )
     return output
 
-def _runfiles_root_path(ctx, path):
-    # The ../ comes from short_path for files in other repos.
-    if path.startswith("../"):
-        return path[3:]
+def _runfiles_root_path(ctx, short_path):
+    """Compute a runfiles-root relative path from `File.short_path`
+
+    Args:
+        ctx: current target ctx
+        short_path: str, a main-repo relative path from `File.short_path`
+
+    Returns:
+        {type}`str`, a runflies-root relative path
+    """
+
+    # The ../ comes from short_path is for files in other repos.
+    if short_path.startswith("../"):
+        return short_path[3:]
     else:
-        return "{}/{}".format(ctx.workspace_name, path)
+        return "{}/{}".format(ctx.workspace_name, short_path)
 
 def _create_stage1_bootstrap(
         ctx,
@@ -512,7 +526,7 @@ def _create_stage1_bootstrap(
         python_binary_path = runtime_details.executable_interpreter_path
 
     if is_for_zip and venv:
-        python_binary_actual = _runfiles_root_path(ctx, venv.interpreter_actual_path)
+        python_binary_actual = venv.interpreter_actual_path
     else:
         python_binary_actual = ""
 

python/private/stage1_bootstrap_template.sh

@@ -135,6 +135,7 @@ fi
 if [[ ! -x "$python_exe" ]]; then
   if [[ ! -e "$python_exe" ]]; then
     echo >&2 "ERROR: Python interpreter not found: $python_exe"
+    ls -l $python_exe >&2
     exit 1
   elif [[ ! -x "$python_exe" ]]; then
     echo >&2 "ERROR: Python interpreter not executable: $python_exe"