Add support for extensionless Python files for server (#13326)

## Summary

Closes: #12539 

## Test Plan

https://github.com/user-attachments/assets/e49b2669-6f12-4684-9e45-a3321b19b659

crates/ruff_server/src/edit.rs

@@ -11,8 +11,8 @@ use lsp_types::{PositionEncodingKind, Url};
 pub use notebook::NotebookDocument;
 pub(crate) use range::{NotebookRange, RangeExt, ToRangeExt};
 pub(crate) use replacement::Replacement;
-pub(crate) use text_document::DocumentVersion;
 pub use text_document::TextDocument;
+pub(crate) use text_document::{DocumentVersion, LanguageId};
 
 use crate::{fix::Fixes, session::ResolvedClientCapabilities};
 

crates/ruff_server/src/edit/text_document.rs

@@ -20,6 +20,23 @@ pub struct TextDocument {
     /// The latest version of the document, set by the LSP client. The server will panic in
     /// debug mode if we attempt to update the document with an 'older' version.
     version: DocumentVersion,
+    /// The language ID of the document as provided by the client.
+    language_id: Option<LanguageId>,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum LanguageId {
+    Python,
+    Other,
+}
+
+impl From<&str> for LanguageId {
+    fn from(language_id: &str) -> Self {
+        match language_id {
+            "python" => Self::Python,
+            _ => Self::Other,
+        }
+    }
 }
 
 impl TextDocument {
@@ -29,9 +46,16 @@ impl TextDocument {
             contents,
             index,
             version,
+            language_id: None,
         }
     }
 
+    #[must_use]
+    pub fn with_language_id(mut self, language_id: &str) -> Self {
+        self.language_id = Some(LanguageId::from(language_id));
+        self
+    }
+
     pub fn into_contents(self) -> String {
         self.contents
     }
@@ -48,6 +72,10 @@ impl TextDocument {
         self.version
     }
 
+    pub fn language_id(&self) -> Option<LanguageId> {
+        self.language_id
+    }
+
     pub fn apply_changes(
         &mut self,
         changes: Vec<lsp_types::TextDocumentContentChangeEvent>,

crates/ruff_server/src/fix.rs

@@ -38,6 +38,7 @@ pub(crate) fn fix_all(
             file_resolver_settings,
             Some(linter_settings),
             None,
+            query.text_document_language_id(),
         ) {
             return Ok(Fixes::default());
         }

crates/ruff_server/src/lint.rs

@@ -77,6 +77,7 @@ pub(crate) fn check(
             file_resolver_settings,
             Some(linter_settings),
             None,
+            query.text_document_language_id(),
         ) {
             return DiagnosticsMap::default();
         }

crates/ruff_server/src/resolve.rs

@@ -4,6 +4,8 @@ use ruff_linter::settings::LinterSettings;
 use ruff_workspace::resolver::{match_any_exclusion, match_any_inclusion};
 use ruff_workspace::{FileResolverSettings, FormatterSettings};
 
+use crate::edit::LanguageId;
+
 /// Return `true` if the document at the given [`Path`] should be excluded.
 ///
 /// The tool-specific settings should be provided if the request for the document is specific to
@@ -19,6 +21,7 @@ pub(crate) fn is_document_excluded(
     resolver_settings: &FileResolverSettings,
     linter_settings: Option<&LinterSettings>,
     formatter_settings: Option<&FormatterSettings>,
+    language_id: Option<LanguageId>,
 ) -> bool {
     if let Some(exclusion) = match_any_exclusion(
         path,
@@ -38,8 +41,14 @@ pub(crate) fn is_document_excluded(
     ) {
         tracing::debug!("Included path via `{}`: {}", inclusion, path.display());
         false
+    } else if let Some(LanguageId::Python) = language_id {
+        tracing::debug!("Included path via Python language ID: {}", path.display());
+        false
     } else {
-        // Path is excluded by not being in the inclusion set.
+        tracing::debug!(
+            "Ignored path as it's not in the inclusion set: {}",
+            path.display()
+        );
         true
     }
 }

crates/ruff_server/src/server/api/notifications/did_open.rs

@@ -21,11 +21,14 @@ impl super::SyncNotificationHandler for DidOpen {
         types::DidOpenTextDocumentParams {
             text_document:
                 types::TextDocumentItem {
-                    uri, text, version, ..
+                    uri,
+                    text,
+                    version,
+                    language_id,
                 },
         }: types::DidOpenTextDocumentParams,
     ) -> Result<()> {
-        let document = TextDocument::new(text, version);
+        let document = TextDocument::new(text, version).with_language_id(&language_id);
 
         session.open_text_document(uri.clone(), document);
 

crates/ruff_server/src/server/api/requests/format.rs

@@ -90,6 +90,7 @@ fn format_text_document(
             file_resolver_settings,
             None,
             Some(formatter_settings),
+            text_document.language_id(),
         ) {
             return Ok(None);
         }

crates/ruff_server/src/server/api/requests/format_range.rs

@@ -54,6 +54,7 @@ fn format_text_document_range(
             file_resolver_settings,
             None,
             Some(formatter_settings),
+            text_document.language_id(),
         ) {
             return Ok(None);
         }

crates/ruff_server/src/session/index.rs

@@ -9,6 +9,7 @@ use rustc_hash::FxHashMap;
 
 pub(crate) use ruff_settings::RuffSettings;
 
+use crate::edit::LanguageId;
 use crate::{
     edit::{DocumentKey, DocumentVersion, NotebookDocument},
     PositionEncoding, TextDocument,
@@ -603,4 +604,12 @@ impl DocumentQuery {
                 .and_then(|cell_uri| notebook.cell_document_by_uri(cell_uri)),
         }
     }
+
+    pub(crate) fn text_document_language_id(&self) -> Option<LanguageId> {
+        if let DocumentQuery::Text { document, .. } = self {
+            document.language_id()
+        } else {
+            None
+        }
+    }
 }