fix(system_python): write import paths to generated file instead of using PYTHONPATH

python/private/py_executable.bzl

@@ -332,9 +332,10 @@ def _create_executable(
     # BuiltinPyRuntimeInfo providers, which is likely to come from
     # @bazel_tools//tools/python:autodetecting_toolchain, the toolchain used
     # for workspace builds when no rules_python toolchain is configured.
-    if (BootstrapImplFlag.get_value(ctx) == BootstrapImplFlag.SCRIPT and
+    if (
         runtime_details.effective_runtime and
-        hasattr(runtime_details.effective_runtime, "stage2_bootstrap_template")):
+        hasattr(runtime_details.effective_runtime, "stage2_bootstrap_template")
+    ):
         venv = _create_venv(
             ctx,
             output_prefix = base_executable_name,
@@ -351,7 +352,11 @@ def _create_executable(
             runtime_details = runtime_details,
             venv = venv,
         )
-        extra_runfiles = ctx.runfiles([stage2_bootstrap] + venv.files_without_interpreter)
+        extra_runfiles = ctx.runfiles(
+            [stage2_bootstrap] + (
+                venv.files_without_interpreter if venv else []
+            ),
+        )
         zip_main = _create_zip_main(
             ctx,
             stage2_bootstrap = stage2_bootstrap,
@@ -469,7 +474,10 @@ def _create_executable(
     )
 
 def _create_zip_main(ctx, *, stage2_bootstrap, runtime_details, venv):
-    python_binary = runfiles_root_path(ctx, venv.interpreter.short_path)
+    if venv.interpreter:
+        python_binary = runfiles_root_path(ctx, venv.interpreter.short_path)
+    else:
+        python_binary = ""
     python_binary_actual = venv.interpreter_actual_path
 
     # The location of this file doesn't really matter. It's added to
@@ -529,62 +537,66 @@ def relative_path(from_, to):
 # * https://github.com/python/cpython/blob/main/Modules/getpath.py
 # * https://github.com/python/cpython/blob/main/Lib/site.py
 def _create_venv(ctx, output_prefix, imports, runtime_details):
+    create_full_venv = BootstrapImplFlag.get_value(ctx) == BootstrapImplFlag.SCRIPT
     venv = "_{}.venv".format(output_prefix.lstrip("_"))
 
-    # The pyvenv.cfg file must be present to trigger the venv site hooks.
-    # Because it's paths are expected to be absolute paths, we can't reliably
-    # put much in it. See https://github.com/python/cpython/issues/83650
-    pyvenv_cfg = ctx.actions.declare_file("{}/pyvenv.cfg".format(venv))
-    ctx.actions.write(pyvenv_cfg, "")
+    if create_full_venv:
+        # The pyvenv.cfg file must be present to trigger the venv site hooks.
+        # Because it's paths are expected to be absolute paths, we can't reliably
+        # put much in it. See https://github.com/python/cpython/issues/83650
+        pyvenv_cfg = ctx.actions.declare_file("{}/pyvenv.cfg".format(venv))
+        ctx.actions.write(pyvenv_cfg, "")
+    else:
+        pyvenv_cfg = None
 
     runtime = runtime_details.effective_runtime
 
     venvs_use_declare_symlink_enabled = (
         VenvsUseDeclareSymlinkFlag.get_value(ctx) == VenvsUseDeclareSymlinkFlag.YES
     )
     recreate_venv_at_runtime = False
-    bin_dir = "{}/bin".format(venv)
-
-    if not venvs_use_declare_symlink_enabled or not runtime.supports_build_time_venv:
-        recreate_venv_at_runtime = True
-        if runtime.interpreter:
-            interpreter_actual_path = runfiles_root_path(ctx, runtime.interpreter.short_path)
-        else:
-            interpreter_actual_path = runtime.interpreter_path
 
-        py_exe_basename = paths.basename(interpreter_actual_path)
+    if runtime.interpreter:
+        interpreter_actual_path = runfiles_root_path(ctx, runtime.interpreter.short_path)
+    else:
+        interpreter_actual_path = runtime.interpreter_path
 
-        # When the venv symlinks are disabled, the $venv/bin/python3 file isn't
-        # needed or used at runtime. However, the zip code uses the interpreter
-        # File object to figure out some paths.
-        interpreter = ctx.actions.declare_file("{}/{}".format(bin_dir, py_exe_basename))
-        ctx.actions.write(interpreter, "actual:{}".format(interpreter_actual_path))
+    bin_dir = "{}/bin".format(venv)
 
-    elif runtime.interpreter:
+    if create_full_venv:
         # Some wrappers around the interpreter (e.g. pyenv) use the program
         # name to decide what to do, so preserve the name.
-        py_exe_basename = paths.basename(runtime.interpreter.short_path)
+        py_exe_basename = paths.basename(interpreter_actual_path)
 
-        # Even though ctx.actions.symlink() is used, using
-        # declare_symlink() is required to ensure that the resulting file
-        # 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("{}/{}".format(bin_dir, py_exe_basename))
+        if not venvs_use_declare_symlink_enabled or not runtime.supports_build_time_venv:
+            recreate_venv_at_runtime = True
 
-        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,
-        )
+            # When the venv symlinks are disabled, the $venv/bin/python3 file isn't
+            # needed or used at runtime. However, the zip code uses the interpreter
+            # File object to figure out some paths.
+            interpreter = ctx.actions.declare_file("{}/{}".format(bin_dir, py_exe_basename))
+            ctx.actions.write(interpreter, "actual:{}".format(interpreter_actual_path))
+
+        elif runtime.interpreter:
+            # Even though ctx.actions.symlink() is used, using
+            # declare_symlink() is required to ensure that the resulting file
+            # 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("{}/{}".format(bin_dir, py_exe_basename))
+
+            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)
+            ctx.actions.symlink(output = interpreter, target_path = rel_path)
+        else:
+            interpreter = ctx.actions.declare_symlink("{}/{}".format(bin_dir, py_exe_basename))
+            ctx.actions.symlink(output = interpreter, target_path = runtime.interpreter_path)
     else:
-        py_exe_basename = paths.basename(runtime.interpreter_path)
-        interpreter = ctx.actions.declare_symlink("{}/{}".format(bin_dir, py_exe_basename))
-        ctx.actions.symlink(output = interpreter, target_path = runtime.interpreter_path)
-        interpreter_actual_path = runtime.interpreter_path
+        interpreter = None
 
     if runtime.interpreter_version_info:
         version = "{}.{}".format(
@@ -626,12 +638,19 @@ def _create_venv(ctx, output_prefix, imports, runtime_details):
     }
     venv_symlinks = _create_venv_symlinks(ctx, venv_dir_map)
 
+    files_without_interpreter = [pth, site_init] + venv_symlinks
+    if pyvenv_cfg:
+        files_without_interpreter.append(pyvenv_cfg)
+
     return struct(
+        # File or None; the `bin/python3` executable in the venv.
+        # None if a full venv isn't created.
         interpreter = interpreter,
+        # bool; True if the venv should be recreated at runtime
         recreate_venv_at_runtime = recreate_venv_at_runtime,
         # Runfiles root relative path or absolute path
         interpreter_actual_path = interpreter_actual_path,
-        files_without_interpreter = [pyvenv_cfg, pth, site_init] + venv_symlinks,
+        files_without_interpreter = files_without_interpreter,
         # string; venv-relative path to the site-packages directory.
         venv_site_packages = venv_site_packages,
     )
@@ -758,7 +777,7 @@ def _create_stage2_bootstrap(
     template = runtime.stage2_bootstrap_template
 
     if main_py:
-        main_py_path = "{}/{}".format(ctx.workspace_name, main_py.short_path)
+        main_py_path = runfiles_root_path(ctx, main_py.short_path)
     else:
         main_py_path = ""