Include document specific debug info (#16215)

## Summary

Related https://github.com/astral-sh/ruff-vscode/pull/692.

## Test Plan

**When there's no active text document:**

```
[Info  - 10:57:03 PM] Global:
executable = /Users/dhruv/work/astral/ruff/target/debug/ruff
version = 0.9.6
position_encoding = UTF16
workspace_root_folders = [
    "/Users/dhruv/playground/ruff",
]
indexed_configuration_files = [
    "/Users/dhruv/playground/ruff/pyproject.toml",
    "/Users/dhruv/playground/ruff/formatter/ruff.toml",
]
open_documents = 0
client_capabilities = ResolvedClientCapabilities {
    code_action_deferred_edit_resolution: true,
    apply_edit: true,
    document_changes: true,
    workspace_refresh: true,
    pull_diagnostics: true,
}

global_client_settings = ResolvedClientSettings {
    fix_all: true,
    organize_imports: true,
    lint_enable: true,
    disable_rule_comment_enable: true,
    fix_violation_enable: true,
    show_syntax_errors: true,
    editor_settings: ResolvedEditorSettings {
        configuration: None,
        lint_preview: None,
        format_preview: None,
        select: None,
        extend_select: None,
        ignore: None,
        exclude: None,
        line_length: None,
        configuration_preference: EditorFirst,
    },
}
```

**When there's an active text document that's been passed as param:**

```
[Info  - 10:53:33 PM] Global:
executable = /Users/dhruv/work/astral/ruff/target/debug/ruff
version = 0.9.6
position_encoding = UTF16
workspace_root_folders = [
    "/Users/dhruv/playground/ruff",
]
indexed_configuration_files = [
    "/Users/dhruv/playground/ruff/pyproject.toml",
    "/Users/dhruv/playground/ruff/formatter/ruff.toml",
]
open_documents = 1
client_capabilities = ResolvedClientCapabilities {
    code_action_deferred_edit_resolution: true,
    apply_edit: true,
    document_changes: true,
    workspace_refresh: true,
    pull_diagnostics: true,
}

Document:
uri = file:///Users/dhruv/playground/ruff/lsp/play.py
kind = Text
version = 1
client_settings = ResolvedClientSettings {
    fix_all: true,
    organize_imports: true,
    lint_enable: true,
    disable_rule_comment_enable: true,
    fix_violation_enable: true,
    show_syntax_errors: true,
    editor_settings: ResolvedEditorSettings {
        configuration: None,
        lint_preview: None,
        format_preview: None,
        select: None,
        extend_select: None,
        ignore: None,
        exclude: None,
        line_length: None,
        configuration_preference: EditorFirst,
    },
}
config_path = Some("/Users/dhruv/playground/ruff/pyproject.toml")

...
```

Replace `...` at the end with the output of `ruff check --show-settings
path.py`

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

@@ -1,3 +1,4 @@
+use std::fmt::Write;
 use std::str::FromStr;
 
 use crate::edit::WorkspaceEditTracker;
@@ -5,10 +6,10 @@ use crate::server::api::LSPResult;
 use crate::server::schedule::Task;
 use crate::server::{client, SupportedCommand};
 use crate::session::Session;
-use crate::DIAGNOSTIC_NAME;
 use crate::{edit::DocumentVersion, server};
+use crate::{DocumentKey, DIAGNOSTIC_NAME};
 use lsp_server::ErrorCode;
-use lsp_types::{self as types, request as req};
+use lsp_types::{self as types, request as req, TextDocumentIdentifier};
 use serde::Deserialize;
 
 pub(crate) struct ExecuteCommand;
@@ -19,6 +20,17 @@ struct Argument {
     version: DocumentVersion,
 }
 
+/// The argument schema for the `ruff.printDebugInformation` command.
+#[derive(Default, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct DebugCommandArgument {
+    /// The URI of the document to print debug information for.
+    ///
+    /// When provided, both document-specific debug information and global information are printed.
+    /// If not provided ([None]), only global debug information is printed.
+    text_document: Option<TextDocumentIdentifier>,
+}
+
 impl super::RequestHandler for ExecuteCommand {
     type RequestType = req::ExecuteCommand;
 }
@@ -34,7 +46,12 @@ impl super::SyncRequestHandler for ExecuteCommand {
             .with_failure_code(ErrorCode::InvalidParams)?;
 
         if command == SupportedCommand::Debug {
-            let output = debug_information(session);
+            let argument: DebugCommandArgument = params.arguments.into_iter().next().map_or_else(
+                || Ok(DebugCommandArgument::default()),
+                |value| serde_json::from_value(value).with_failure_code(ErrorCode::InvalidParams),
+            )?;
+            let output = debug_information(session, argument.text_document)
+                .with_failure_code(ErrorCode::InternalError)?;
             notifier
                 .notify::<types::notification::LogMessage>(types::LogMessageParams {
                     message: output.clone(),
@@ -134,23 +151,71 @@ fn apply_edit(
     )
 }
 
-fn debug_information(session: &Session) -> String {
+/// Returns a string with debug information about the session and the document at the given URI.
+fn debug_information(
+    session: &Session,
+    text_document: Option<TextDocumentIdentifier>,
+) -> crate::Result<String> {
     let executable = std::env::current_exe()
         .map(|path| format!("{}", path.display()))
         .unwrap_or_else(|_| "<unavailable>".to_string());
-    format!(
+
-        "executable = {executable}
+    let mut buffer = String::new();
+
+    writeln!(
+        buffer,
+        "Global:
+executable = {executable}
 version = {version}
-encoding = {encoding:?}
+position_encoding = {encoding:?}
-open_document_count = {doc_count}
+workspace_root_folders = {workspace_folders:#?}
-active_workspace_count = {workspace_count}
+indexed_configuration_files = {config_files:#?}
-configuration_files = {config_files:?}
+open_documents_len = {open_documents_len}
-{client_capabilities}",
+client_capabilities = {client_capabilities:#?}
+",
         version = crate::version(),
         encoding = session.encoding(),
+        workspace_folders = session.workspace_root_folders().collect::<Vec<_>>(),
+        config_files = session.config_file_paths().collect::<Vec<_>>(),
+        open_documents_len = session.open_documents_len(),
         client_capabilities = session.resolved_client_capabilities(),
-        doc_count = session.num_documents(),
+    )?;
-        workspace_count = session.num_workspaces(),
+
-        config_files = session.list_config_files()
+    if let Some(TextDocumentIdentifier { uri }) = text_document {
-    )
+        let Some(snapshot) = session.take_snapshot(uri.clone()) else {
+            writeln!(buffer, "Unable to take a snapshot of the document at {uri}")?;
+            return Ok(buffer);
+        };
+        let query = snapshot.query();
+
+        writeln!(
+            buffer,
+            "Open document:
+uri = {uri}
+kind = {kind}
+version = {version}
+client_settings = {client_settings:#?}
+config_path = {config_path:?}
+{settings}
+            ",
+            uri = uri.clone(),
+            kind = match session.key_from_url(uri) {
+                DocumentKey::Notebook(_) => "Notebook",
+                DocumentKey::NotebookCell(_) => "NotebookCell",
+                DocumentKey::Text(_) => "Text",
+            },
+            version = query.version(),
+            client_settings = snapshot.client_settings(),
+            config_path = query.settings().path(),
+            settings = query.settings(),
+        )?;
+    } else {
+        writeln!(
+            buffer,
+            "global_client_settings = {:#?}",
+            session.global_client_settings()
+        )?;
+    }
+
+    Ok(buffer)
 }

crates/ruff_server/src/session.rs

@@ -1,8 +1,10 @@
 //! Data model, state management, and configuration resolution.
 
+use std::path::Path;
 use std::sync::Arc;
 
 use lsp_types::{ClientCapabilities, FileEvent, NotebookDocumentCellChange, Url};
+use settings::ResolvedClientSettings;
 
 use crate::edit::{DocumentKey, DocumentVersion, NotebookDocument};
 use crate::server::Workspaces;
@@ -147,18 +149,6 @@ impl Session {
         Ok(())
     }
 
-    pub(crate) fn num_documents(&self) -> usize {
-        self.index.num_documents()
-    }
-
-    pub(crate) fn num_workspaces(&self) -> usize {
-        self.index.num_workspaces()
-    }
-
-    pub(crate) fn list_config_files(&self) -> Vec<&std::path::Path> {
-        self.index.list_config_files()
-    }
-
     pub(crate) fn resolved_client_capabilities(&self) -> &ResolvedClientCapabilities {
         &self.resolved_client_capabilities
     }
@@ -166,6 +156,26 @@ impl Session {
     pub(crate) fn encoding(&self) -> PositionEncoding {
         self.position_encoding
     }
+
+    /// Returns an iterator over the paths to the configuration files in the index.
+    pub(crate) fn config_file_paths(&self) -> impl Iterator<Item = &Path> {
+        self.index.config_file_paths()
+    }
+
+    /// Returns the resolved global client settings.
+    pub(crate) fn global_client_settings(&self) -> ResolvedClientSettings {
+        ResolvedClientSettings::global(&self.global_settings)
+    }
+
+    /// Returns the number of open documents in the session.
+    pub(crate) fn open_documents_len(&self) -> usize {
+        self.index.open_documents_len()
+    }
+
+    /// Returns an iterator over the workspace root folders in the session.
+    pub(crate) fn workspace_root_folders(&self) -> impl Iterator<Item = &Path> {
+        self.index.workspace_root_folders()
+    }
 }
 
 impl DocumentSnapshot {

crates/ruff_server/src/session/index.rs

@@ -177,21 +177,6 @@ impl Index {
             .register_workspace(&Workspace::new(url), global_settings)
     }
 
-    pub(super) fn num_documents(&self) -> usize {
-        self.documents.len()
-    }
-
-    pub(super) fn num_workspaces(&self) -> usize {
-        self.settings.len()
-    }
-
-    pub(super) fn list_config_files(&self) -> Vec<&Path> {
-        self.settings
-            .values()
-            .flat_map(|WorkspaceSettings { ruff_settings, .. }| ruff_settings.list_files())
-            .collect()
-    }
-
     pub(super) fn close_workspace_folder(&mut self, workspace_url: &Url) -> crate::Result<()> {
         let workspace_path = workspace_url.to_file_path().map_err(|()| {
             anyhow!("Failed to convert workspace URL to file path: {workspace_url}")
@@ -404,6 +389,23 @@ impl Index {
             .next_back()
             .map(|(_, settings)| settings)
     }
+
+    /// Returns an iterator over the workspace root folders contained in this index.
+    pub(super) fn workspace_root_folders(&self) -> impl Iterator<Item = &Path> {
+        self.settings.keys().map(PathBuf::as_path)
+    }
+
+    /// Returns the number of open documents.
+    pub(super) fn open_documents_len(&self) -> usize {
+        self.documents.len()
+    }
+
+    /// Returns an iterator over the paths to the configuration files in the index.
+    pub(super) fn config_file_paths(&self) -> impl Iterator<Item = &Path> {
+        self.settings
+            .values()
+            .flat_map(|WorkspaceSettings { ruff_settings, .. }| ruff_settings.config_file_paths())
+    }
 }
 
 /// Maps a workspace folder root to its settings.

crates/ruff_server/src/session/index/ruff_settings.rs

@@ -20,6 +20,7 @@ use ruff_workspace::{
 
 use crate::session::settings::{ConfigurationPreference, ResolvedEditorSettings};
 
+#[derive(Debug)]
 pub struct RuffSettings {
     /// The path to this configuration file, used for debugging.
     /// The default fallback configuration does not have a file path.
@@ -28,6 +29,12 @@ pub struct RuffSettings {
     settings: Settings,
 }
 
+impl RuffSettings {
+    pub(crate) fn path(&self) -> Option<&Path> {
+        self.path.as_deref()
+    }
+}
+
 impl Deref for RuffSettings {
     type Target = Settings;
 
@@ -298,15 +305,16 @@ impl RuffSettingsIndex {
             .clone()
     }
 
-    pub(crate) fn list_files(&self) -> impl Iterator<Item = &Path> {
+    pub(super) fn fallback(&self) -> Arc<RuffSettings> {
+        self.fallback.clone()
+    }
+
+    /// Returns an iterator over the paths to the configuration files in the index.
+    pub(crate) fn config_file_paths(&self) -> impl Iterator<Item = &Path> {
         self.index
             .values()
             .filter_map(|settings| settings.path.as_deref())
     }
-
-    pub(super) fn fallback(&self) -> Arc<RuffSettings> {
-        self.fallback.clone()
-    }
 }
 
 struct EditorConfigurationTransformer<'a>(&'a ResolvedEditorSettings, &'a Path);