When determining the python module name, use pyproject.toml `project.…

…name` over Cargo.toml `package.name`.

I propose to change the precedence for determining the module name to consider before pyproject.toml `project.name` over Cargo.toml `package.name`. This came up in ruff (astral-sh/ruff#4397, astral-sh/ruff#4399), where the crate name is `ruff_cli` and the project name is `ruff`.

I'm not sure if there are any cases a user would like the crate name over the package name.

Changelog.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+ * When determining the python module name, use pyproject.toml `project.name` over Cargo.toml `package.name`.
+
 ## [0.15.1] - 2023-05-07
 
 * Fix finding interpreters from bundled sysconfigs in [#1598](https://github.com/PyO3/maturin/pull/1598)

src/project_layout.rs

@@ -119,17 +119,20 @@ impl ProjectResolver {
 
         // If the package name contains minuses, you must declare a module with
         // underscores as lib name
-        let module_name = cargo_toml
-            .lib
-            .as_ref()
-            .and_then(|lib| lib.name.as_ref())
+        // Precedence:
+        //  * Explicitly declared pyproject.toml `tool.maturin.module-name`
+        //  * Cargo.toml `lib.name`
+        //  * pyproject.toml `project.name`
+        //  * Cargo.toml `package.name`
+        let module_name = pyproject
+            .and_then(|x| x.module_name())
+            .or(cargo_toml.lib.as_ref().and_then(|lib| lib.name.as_deref()))
+            .or(pyproject
+                .and_then(|pyproject| pyproject.project.as_ref())
+                .map(|project| project.name.as_str()))
             .unwrap_or(crate_name)
             .to_owned();
 
-        let extension_name = pyproject
-            .and_then(|x| x.module_name())
-            .unwrap_or(&module_name);
-
         let project_root = if pyproject_file.is_file() {
             pyproject_file.parent().unwrap_or(manifest_dir)
         } else {
@@ -176,7 +179,7 @@ impl ProjectResolver {
             }
         });
         let project_layout =
-            ProjectLayout::determine(project_root, extension_name, py_root, python_packages, data)?;
+            ProjectLayout::determine(project_root, &module_name, py_root, python_packages, data)?;
         Ok(Self {
             project_layout,
             cargo_toml_path: manifest_file,