Re-export __all__ in __init__.py for pure Rust project

Changelog.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+* Re-export `__all__` for pure Rust projects in [#886](https://github.com/PyO3/maturin/pull/886)
+
 ## [0.12.14] - 2022-04-25
 
 * Fix PyPy pep517 build when abi3 feature is enabled in [#883](https://github.com/PyO3/maturin/pull/883)

guide/src/project_layout.md

@@ -22,7 +22,9 @@ wheel. For convenience, this file includes the following:
 ```python
 from .my_project import *
 
-__doc__ = .my_project.__doc__
+__doc__ = my_project.__doc__
+if hasattr(my_project, "__all__"):
+    __all__ = my_project.__all__
 ```
 
 such that the module functions may be called directly with:

src/module_writer.rs

@@ -656,7 +656,11 @@ pub fn write_bindings_module(
             writer.add_bytes(
                 &module.join("__init__.py"),
                 format!(
-                    "from .{module_name} import *\n\n__doc__ = {module_name}.__doc__\n",
+                    r#"from .{module_name} import *
+
+__doc__ = {module_name}.__doc__
+if hasattr({module_name}, "__all__"):
+    __all__ = {module_name}.__all__"#,
                     module_name = module_name
                 )
                 .as_bytes(),

src/templates/__init__.py.j2

@@ -2,3 +2,5 @@ from .{{ crate_name }} import *
 
 
 __doc__ = {{ crate_name }}.__doc__
+if hasattr({{ crate_name }}, "__all__"):
+	__all__ = {{ crate_name }}.__all__