test: add Mac Xcode locator coverage (#429)

Adds focused direct coverage for the Mac Xcode locator while continuing
the #389 coverage work.

- Adds deterministic tests for Xcode path matching, locator metadata,
and non-macOS rejection.
- Corrects MacXCode supported categories to report MacXCode.
- Narrows Xcode path classification to Xcode*.app Python executables
under the expected usr/bin or framework layouts.

Validation:
- cargo fmt --all
- wsl bash -lc 'cd /mnt/c/GIT/projects/python-environment-tools && cargo
test -p pet-mac-xcode'
- wsl bash -lc 'cd /mnt/c/GIT/projects/python-environment-tools && cargo
clippy --all -- -D warnings'

Refs #389

Author: karthiknadig

crates/pet-mac-xcode/src/lib.rs

@@ -31,7 +31,7 @@ impl Locator for MacXCode {
         LocatorKind::MacXCode
     }
     fn supported_categories(&self) -> Vec<PythonEnvironmentKind> {
-        vec![PythonEnvironmentKind::MacCommandLineTools]
+        vec![PythonEnvironmentKind::MacXCode]
     }
 
     fn try_from(&self, env: &PythonEnv) -> Option<PythonEnvironment> {
@@ -49,8 +49,7 @@ impl Locator for MacXCode {
 
         // Support for /Applications/Xcode.app/Contents/Developer/usr/bin/python3
         // /Applications/Xcode_15.0.1.app/Contents/Developer/usr/bin/python3 (such paths are on CI, see here https://github.com/microsoft/python-environment-tools/issues/38)
-        if !exe_str.starts_with("/Applications") && !exe_str.contains("Contents/Developer/usr/bin")
-        {
+        if !is_xcode_python_path(&exe_str) {
             return None;
         }
 
@@ -231,3 +230,230 @@ impl Locator for MacXCode {
         // }
     }
 }
+
+fn is_xcode_python_path(executable: &str) -> bool {
+    let Some(rest) = executable.strip_prefix("/Applications/") else {
+        return false;
+    };
+
+    let Some(app_bundle) = rest.split('/').next() else {
+        return false;
+    };
+
+    if !app_bundle.starts_with("Xcode") || !app_bundle.ends_with(".app") {
+        return false;
+    }
+
+    let app_relative_path = &rest[app_bundle.len()..];
+    if let Some(usr_bin_entry) = app_relative_path.strip_prefix("/Contents/Developer/usr/bin/") {
+        return is_macos_python_executable_name(usr_bin_entry) && !usr_bin_entry.contains('/');
+    }
+
+    let Some(framework_entry) = app_relative_path
+        .strip_prefix("/Contents/Developer/Library/Frameworks/Python3.framework/Versions/")
+    else {
+        return false;
+    };
+
+    let mut framework_parts = framework_entry.split('/');
+    framework_parts
+        .next()
+        .is_some_and(is_macos_framework_version_dir)
+        && framework_parts.next() == Some("bin")
+        && framework_parts
+            .next()
+            .is_some_and(is_macos_python_executable_name)
+        && framework_parts.next().is_none()
+}
+
+fn is_macos_python_executable_name(executable: &str) -> bool {
+    if executable == "python" || executable == "python3" {
+        return true;
+    }
+
+    let Some(minor) = executable.strip_prefix("python3.") else {
+        return false;
+    };
+
+    !minor.is_empty() && minor.chars().all(|ch| ch.is_ascii_digit())
+}
+
+fn is_macos_framework_version_dir(version: &str) -> bool {
+    if version == "Current" {
+        return true;
+    }
+
+    let mut parts = version.split('.');
+    parts
+        .next()
+        .is_some_and(|major| !major.is_empty() && major.chars().all(|ch| ch.is_ascii_digit()))
+        && parts
+            .next()
+            .is_some_and(|minor| !minor.is_empty() && minor.chars().all(|ch| ch.is_ascii_digit()))
+        && parts.next().is_none()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pet_core::Locator;
+
+    #[test]
+    fn locator_metadata_matches_xcode_kind() {
+        let locator = MacXCode::new();
+
+        assert_eq!(locator.get_kind(), LocatorKind::MacXCode);
+        assert_eq!(
+            locator.supported_categories(),
+            vec![PythonEnvironmentKind::MacXCode]
+        );
+    }
+
+    #[test]
+    fn xcode_path_accepts_default_xcode_usr_bin_python() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_accepts_versioned_xcode_usr_bin_python() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode_15.0.1.app/Contents/Developer/usr/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_accepts_default_xcode_usr_bin_python_without_version() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/python"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_accepts_default_xcode_usr_bin_versioned_python() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/python3.12"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_accepts_framework_python_executable() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/bin/python3.9"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_accepts_framework_python_executable_in_current_version_dir() {
+        assert!(is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/Current/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_non_python_framework_path() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/Resources/Info.plist"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_python_config_script() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/python-config"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_versioned_python_config_script() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/bin/python3.9-config"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_framework_python_executable_in_invalid_version_dir() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/Foo/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_framework_python_executable_in_patch_version_dir() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9.0/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_multi_dot_python_executable_name() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9/bin/python3.9.0"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_compact_python_version_name() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/python312"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_python_prefixed_tool() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/pythonfoo"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_unrelated_application_python() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Other.app/Contents/MacOS/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_other_application_developer_python() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Other.app/Contents/Developer/usr/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_developer_path_outside_applications() {
+        assert!(!is_xcode_python_path(
+            "/tmp/Xcode.app/Contents/Developer/usr/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_nested_developer_layout() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Nested.app/Contents/Developer/usr/bin/python3"
+        ));
+    }
+
+    #[test]
+    fn xcode_path_rejects_nested_usr_bin_entry() {
+        assert!(!is_xcode_python_path(
+            "/Applications/Xcode.app/Contents/Developer/usr/bin/nested/python3"
+        ));
+    }
+
+    #[cfg(not(target_os = "macos"))]
+    #[test]
+    fn try_from_rejects_xcode_path_off_macos() {
+        let locator = MacXCode::new();
+        let env = PythonEnv::new(
+            PathBuf::from("/Applications/Xcode.app/Contents/Developer/usr/bin/python3"),
+            Some(PathBuf::from(
+                "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.9",
+            )),
+            Some("3.9.6".to_string()),
+        );
+
+        assert!(locator.try_from(&env).is_none());
+    }
+}