feat: Add signature help

crates/roughly/src/index.rs

@@ -245,11 +245,18 @@ fn index_function(
             "fn({})",
             parameters
                 .children_by_field_name("parameter", &mut parameters.walk())
-                .map(|parameter| match parameter.child(0) {
-                    Some(name) => {
-                        rope.byte_slice(name.byte_range()).to_string()
+                .map(|parameter| {
+                    let name = match parameter.child(0) {
+                        Some(name) => rope.byte_slice(name.byte_range()).to_string(),
+                        None => "Unknown".into(),
+                    };
+                    match parameter.child_by_field_name("default") {
+                        Some(default) => {
+                            let default = rope.byte_slice(default.byte_range()).to_string();
+                            format!("{name} = {default}")
+                        }
+                        None => name,
                     }
-                    None => "Unknown".into(),
                 })
                 .collect::<Vec<String>>()
                 .join(", ")

crates/roughly/src/lib.rs

@@ -8,6 +8,7 @@ pub mod index;
 pub mod references;
 pub mod rename;
 pub mod server;
+pub mod signature_help;
 pub mod symbols;
 pub mod tree;
 pub mod utils;

crates/roughly/src/server.rs

@@ -13,12 +13,13 @@ use {
             GlobPattern, InitializeParams, InitializeResult, InitializedParams, Location,
             MessageType, OneOf, Position, PublishDiagnosticsParams, Range, ReferenceParams,
             Registration, RegistrationParams, RelativePattern, RenameParams, SaveOptions,
-            ServerCapabilities, ServerInfo, ShowMessageParams, TextDocumentSyncCapability,
-            TextDocumentSyncKind, TextDocumentSyncOptions, TextDocumentSyncSaveOptions, TextEdit,
-            Url, WorkspaceEdit, WorkspaceSymbolParams, WorkspaceSymbolResponse,
+            ServerCapabilities, ServerInfo, ShowMessageParams, SignatureHelpOptions,
+            SignatureHelpParams, TextDocumentSyncCapability, TextDocumentSyncKind,
+            TextDocumentSyncOptions, TextDocumentSyncSaveOptions, TextEdit, Url, WorkspaceEdit,
+            WorkspaceSymbolParams, WorkspaceSymbolResponse,
             notification::{DidChangeWatchedFiles, Notification},
         },
-        references, rename, symbols, tree, utils,
+        references, rename, signature_help, symbols, tree, utils,
     },
     async_lsp::{
         ClientSocket, ErrorCode, LanguageClient, LanguageServer, ResponseError,
@@ -149,6 +150,11 @@ impl LanguageServer for ServerState {
                     trigger_characters: Some(vec!["$".into(), "@".into(), ":".into()]),
                     ..Default::default()
                 }),
+                signature_help_provider: Some(SignatureHelpOptions {
+                    trigger_characters: Some(vec!["(".into(), ",".into()]),
+                    retrigger_characters: Some(vec![",".into()]),
+                    ..Default::default()
+                }),
                 definition_provider: Some(OneOf::Left(true)),
                 document_formatting_provider: Some(OneOf::Left(true)),
                 document_range_formatting_provider: Some(OneOf::Left(
@@ -425,6 +431,35 @@ impl LanguageServer for ServerState {
         ControlFlow::Continue(())
     }
 
+    //
+    // SIGNATURE HELP
+    //
+
+    fn signature_help(
+        &mut self,
+        params: SignatureHelpParams,
+    ) -> BoxFuture<'static, Result<Option<crate::lsp_types::SignatureHelp>, ResponseError>> {
+        let uri = params.text_document_position_params.text_document.uri;
+        let path = uri.to_file_path().unwrap();
+        let position = params.text_document_position_params.position;
+
+        tracing::debug!(?path, "signature help");
+
+        let Some(document) = self.document_map.get(&path) else {
+            tracing::error!(?path, "document not found");
+            return box_future(Err(path_not_found_error(&path)));
+        };
+
+        let result = signature_help::get(
+            position,
+            &document.rope,
+            &document.tree,
+            &self.workspace_items,
+        );
+
+        box_future(Ok(result))
+    }
+
     //
     // COMPLETION
     //