feat: add support for expanding PROJECT_ROOT in requirement files

Signed-off-by: Amaury Pouly <[email protected]>

Author: pamaury

python/private/pypi/extension.bzl

@@ -241,6 +241,7 @@ def _create_whl_repos(
             group_deps = group_deps,
             group_name = group_name,
             pip_data_exclude = pip_attr.pip_data_exclude,
+            project_root = pip_attr.project_root,
             python_interpreter = pip_attr.python_interpreter,
             python_interpreter_target = python_interpreter_target,
             whl_patches = {
@@ -732,6 +733,9 @@ find in case extra indexes are specified.
 """,
             default = True,
         ),
+        "project_root": attr.label(
+            doc = "Label of the file defining the project root. If present, this label will be passed to all `whl_library` created from the requirement file. It will then expanded to a path and its parent directory will be made available in the PROJECT_ROOT environment variable when building the wheel.",
+        ),
         "python_version": attr.string(
             mandatory = True,
             doc = """

python/private/pypi/whl_library.bzl

@@ -192,6 +192,9 @@ def _whl_library_impl(rctx):
 
     # Manually construct the PYTHONPATH since we cannot use the toolchain here
     environment = _create_repository_execution_environment(rctx, python_interpreter, logger = logger)
+    # Add a PROJECT_ROOT environment variable
+    if rctx.attr.project_root:
+        environment["PROJECT_ROOT"] = str(rctx.path(rctx.attr.project_root).dirname)
 
     whl_path = None
     if rctx.attr.whl_file:
@@ -404,6 +407,9 @@ and the target that we need respectively.
     "group_name": attr.string(
         doc = "Name of the group, if any.",
     ),
+    "project_root": attr.label(
+        doc = "Label of the file defining the project root. If present, this label will be expanded to a path and its parent directory will be made available in the PROJECT_ROOT environment variable when building the wheel.",
+    ),
     "repo": attr.string(
         mandatory = True,
         doc = "Pointer to parent repo name. Used to make these rules rerun if the parent repo changes.",