python: Enable subroot detection for pylsp and pyright (#27364)

This is not going to fully fix the multi-root story, as we still need to
weave venvs through. Hence, no release note just yet.

Release Notes:

- N/A

crates/languages/src/python.rs

@@ -5,12 +5,12 @@ use collections::HashMap;
 use gpui::{App, Task};
 use gpui::{AsyncApp, SharedString};
 use language::language_settings::language_settings;
-use language::LanguageName;
 use language::LanguageToolchainStore;
 use language::Toolchain;
 use language::ToolchainList;
 use language::ToolchainLister;
 use language::{ContextProvider, LspAdapter, LspAdapterDelegate};
+use language::{LanguageName, ManifestName, ManifestProvider, ManifestQuery};
 use lsp::LanguageServerBinary;
 use lsp::LanguageServerName;
 use node_runtime::NodeRuntime;
@@ -35,6 +35,32 @@ use std::{
 use task::{TaskTemplate, TaskTemplates, VariableName};
 use util::ResultExt;
 
+pub(crate) struct PyprojectTomlManifestProvider;
+
+impl ManifestProvider for PyprojectTomlManifestProvider {
+    fn name(&self) -> ManifestName {
+        SharedString::new_static("pyproject.toml").into()
+    }
+
+    fn search(
+        &self,
+        ManifestQuery {
+            path,
+            depth,
+            delegate,
+        }: ManifestQuery,
+    ) -> Option<Arc<Path>> {
+        for path in path.ancestors().take(depth) {
+            let p = path.join("pyproject.toml");
+            if delegate.exists(&p, Some(false)) {
+                return Some(path.into());
+            }
+        }
+
+        None
+    }
+}
+
 const SERVER_PATH: &str = "node_modules/pyright/langserver.index.js";
 const NODE_MODULE_RELATIVE_SERVER_PATH: &str = "pyright/langserver.index.js";
 
@@ -293,6 +319,9 @@ impl LspAdapter for PythonLspAdapter {
             user_settings
         })
     }
+    fn manifest_name(&self) -> Option<ManifestName> {
+        Some(SharedString::new_static("pyproject.toml").into())
+    }
 }
 
 async fn get_cached_server_binary(
@@ -1010,6 +1039,9 @@ impl LspAdapter for PyLspAdapter {
             user_settings
         })
     }
+    fn manifest_name(&self) -> Option<ManifestName> {
+        Some(SharedString::new_static("pyproject.toml").into())
+    }
 }
 
 #[cfg(test)]