Add path option for Python source

Changelog.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+* Add path option for Python source in [#584](https://github.com/PyO3/maturin/pull/584)
+
 ## [0.11.2] - 2021-07-20
 
 * Use UTF-8 encoding when reading `pyproject.toml` by domdfcoding in [#588](https://github.com/PyO3/maturin/pull/588)

Readme.md

@@ -98,6 +98,30 @@ my-project
 ├── my_project
 │   ├── __init__.py
 │   └── bar.py
+├── pyproject.toml
+├── Readme.md
+└── src
+    └── lib.rs
+```
+
+You can specify a different python source directory in `Cargo.toml` by setting `package.metadata.maturin.python-source`, for example
+
+```toml
+[package.metadata.maturin]
+python-source = "python"
+```
+
+then the project structure would look like this:
+
+```
+my-project
+├── Cargo.toml
+├── python
+│   ├── my_project
+│   │   ├── __init__.py
+│   │   ├── __init__.py
+│   │   └── bar.py
+│   └── pyproject.toml
 ├── Readme.md
 └── src
     └── lib.rs

src/build_context.rs

@@ -14,6 +14,7 @@ use crate::Target;
 use anyhow::{anyhow, bail, Context, Result};
 use cargo_metadata::Metadata;
 use fs_err as fs;
+use std::borrow::Cow;
 use std::path::{Path, PathBuf};
 
 /// The way the rust code is used in the wheel
@@ -73,22 +74,29 @@ pub enum ProjectLayout {
 
 impl ProjectLayout {
     /// Checks whether a python module exists besides Cargo.toml with the right name
-    pub fn determine(project_root: impl AsRef<Path>, module_name: &str) -> Result<ProjectLayout> {
+    pub fn determine(
+        project_root: impl AsRef<Path>,
+        module_name: &str,
+        py_src: Option<impl AsRef<Path>>,
+    ) -> Result<ProjectLayout> {
         // A dot in the module name means the extension module goes into the module folder specified by the path
         let parts: Vec<&str> = module_name.split('.').collect();
         let project_root = project_root.as_ref();
+        let python_root = py_src.map_or(Cow::Borrowed(project_root), |py_src| {
+            Cow::Owned(project_root.join(py_src))
+        });
         let (python_module, rust_module, extension_name) = if parts.len() > 1 {
             let mut rust_module = project_root.to_path_buf();
             rust_module.extend(&parts[0..parts.len() - 1]);
             (
-                project_root.join(parts[0]),
+                python_root.join(parts[0]),
                 rust_module,
                 parts[parts.len() - 1].to_string(),
             )
         } else {
             (
-                project_root.join(module_name),
-                project_root.join(module_name),
+                python_root.join(module_name),
+                python_root.join(module_name),
                 module_name.to_string(),
             )
         };

src/build_options.rs

@@ -152,7 +152,11 @@ impl BuildOptions {
             .filter(|name| name.contains('.'))
             .unwrap_or(&module_name);
 
-        let project_layout = ProjectLayout::determine(manifest_dir, extension_name)?;
+        let project_layout = ProjectLayout::determine(
+            manifest_dir,
+            extension_name,
+            extra_metadata.python_source.as_deref(),
+        )?;
 
         let mut cargo_extra_args = split_extra_args(&self.cargo_extra_args)?;
         if let Some(ref target) = self.target {

src/cargo_toml.rs

@@ -123,6 +123,7 @@ pub struct RemainingCoreMetadata {
     pub project_url: Option<HashMap<String, String>>,
     pub provides_extra: Option<Vec<String>>,
     pub description_content_type: Option<String>,
+    pub python_source: Option<String>,
 }
 
 #[cfg(test)]

src/metadata.rs

@@ -3,6 +3,7 @@ use anyhow::{bail, Context, Result};
 use fs_err as fs;
 use regex::Regex;
 use serde::{Deserialize, Serialize};
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 use std::str;
@@ -356,7 +357,14 @@ impl Metadata21 {
             gui_scripts: HashMap::new(),
             entry_points: HashMap::new(),
         };
-        metadata.merge_pyproject_toml(manifest_path)?;
+
+        let manifest_path = manifest_path.as_ref();
+        let py_src = extra_metadata
+            .python_source
+            .map_or(Cow::Borrowed(manifest_path), |src| {
+                Cow::Owned(manifest_path.join(src))
+            });
+        metadata.merge_pyproject_toml(&*py_src)?;
         Ok(metadata)
     }
 
@@ -776,4 +784,20 @@ mod test {
         let pkginfo: Result<python_pkginfo::Metadata, _> = content.parse();
         assert!(pkginfo.is_ok());
     }
+
+    #[test]
+    fn test_merge_metadata_from_pyproject_toml_with_customized_python_source_dir() {
+        let cargo_toml_str =
+            fs_err::read_to_string("test-crates/pyo3-mixed-py-subdir/Cargo.toml").unwrap();
+        let cargo_toml: CargoToml = toml::from_str(&cargo_toml_str).unwrap();
+        let metadata =
+            Metadata21::from_cargo_toml(&cargo_toml, "test-crates/pyo3-mixed-py-subdir").unwrap();
+        // defined in Cargo.toml
+        assert_eq!(
+            metadata.summary,
+            Some("Implements a dummy function combining rust and python".to_string())
+        );
+        // defined in pyproject.toml
+        assert_eq!(metadata.scripts["get_42"], "pyo3_mixed_py_subdir:get_42");
+    }
 }