Refactor StubInfoBuilder to reduce dependence on PyProject

To support generating stubs without a pyproject.toml file, it needs to be possible to build a StubInfo without one. The StubInfo only uses it to find the python root, so that value can be determined earlier in the process and passed along instead of the PyProject.

StubInfoBuilder is not exported, so its ::new() can be renamed without causing backwards incompatibility.

pyo3-stub-gen/src/generate/stub_info.rs

@@ -5,27 +5,22 @@ use std::{collections::BTreeMap, fs, io::Write, path::*};
 #[derive(Debug, Clone, PartialEq)]
 pub struct StubInfo {
     pub modules: BTreeMap<String, Module>,
-    pub pyproject: PyProject,
+    pub python_root: PathBuf,
 }
 
 impl StubInfo {
     pub fn from_pyproject_toml(path: impl AsRef<Path>) -> Result<Self> {
         let pyproject = PyProject::parse_toml(path)?;
-        Ok(StubInfoBuilder::new(pyproject).build())
+        Ok(StubInfoBuilder::from_pyproject_toml(pyproject).build())
     }
 
     pub fn generate(&self) -> Result<()> {
-        let python_root = self
-            .pyproject
-            .python_source()
-            .unwrap_or(PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap()));
-
         for (name, module) in self.modules.iter() {
             let path = name.replace(".", "/");
             let dest = if module.submodules.is_empty() {
-                python_root.join(format!("{path}.pyi"))
+                self.python_root.join(format!("{path}.pyi"))
             } else {
-                python_root.join(path).join("__init__.pyi")
+                self.python_root.join(path).join("__init__.pyi")
             };
 
             let dir = dest.parent().context("Cannot get parent directory")?;
@@ -47,15 +42,17 @@ impl StubInfo {
 struct StubInfoBuilder {
     modules: BTreeMap<String, Module>,
     default_module_name: String,
-    pyproject: PyProject,
+    python_root: PathBuf,
 }
 
 impl StubInfoBuilder {
-    fn new(pyproject: PyProject) -> Self {
+    fn from_pyproject_toml(pyproject: PyProject) -> Self {
         Self {
             modules: BTreeMap::new(),
             default_module_name: pyproject.module_name().to_string(),
-            pyproject,
+            python_root: pyproject
+                .python_source()
+                .unwrap_or(PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap())),
         }
     }
 
@@ -158,7 +155,7 @@ impl StubInfoBuilder {
         self.register_submodules();
         StubInfo {
             modules: self.modules,
-            pyproject: self.pyproject,
+            python_root: self.python_root,
         }
     }
 }