Implement a Language Server for Technique (#79)

Introduce a new top-level command _technique language_ to run a server
for the Language Server Protocol (LSP). This works by consuming JSON-RPC
messages sent over stdin from an editor or IDE and then handling various
methods being invoked. This implementation currently handles reporting
compiler errors and re-formatting the document.

This gave us reason to extend the ranges shown in error messages to more
accurately convey the location of the problematic code. Both the carets
shown in textual errors in _technique check_ and the red squiggle shown
under erroneous code in an IDE benefit from this.

Finally, we've added `-` as a valid filename, indicating that input to
be checked or formatted is to be taken from standard input.

Author: istathar

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "technique"
-version = "0.4.2"
+version = "0.4.3"
 edition = "2021"
 description = "A domain specific language for procedures."
 authors = [ "Andrew Cowie" ]
@@ -9,10 +9,14 @@ license = "MIT"
 
 [dependencies]
 clap = { version = "4.5.16", features = [ "wrap_help" ] }
+lsp-server = "0.7.9"
+lsp-types = "0.95"
 owo-colors = "4"
 regex = "1.11.1"
 serde = { version = "1.0.209", features = [ "derive" ] }
+serde_json = "1.0"
 tinytemplate = "1.2.1"
+
 tracing = "0.1.40"
 tracing-subscriber = { version = "0.3.18", features = [ "env-filter" ] }
 

Cargo.toml

@@ -0,0 +1,37 @@
+use lsp_server::Connection;
+use lsp_types::{
+    InitializeParams, OneOf, ServerCapabilities, TextDocumentSyncCapability, TextDocumentSyncKind,
+};
+use tracing::{debug, info};
+
+mod server;
+
+pub(crate) fn run_language_server() {
+    debug!("Starting Technique Language Server");
+
+    let (connection, threads) = Connection::stdio();
+
+    let capabilities = serde_json::to_value(ServerCapabilities {
+        text_document_sync: Some(TextDocumentSyncCapability::Kind(TextDocumentSyncKind::FULL)),
+        document_formatting_provider: Some(OneOf::Left(true)),
+        ..Default::default()
+    })
+    .unwrap();
+
+    // extract any initialization parameters passed from the editor.
+    if let Ok(params) = connection.initialize(capabilities) {
+        let _params = serde_json::from_value::<InitializeParams>(params).unwrap();
+
+        info!("Technique Language Server starting on stdin");
+
+        let server = server::TechniqueLanguageServer::new();
+
+        if let Err(e) = server.run(connection) {
+            eprintln!("Server error: {}", e);
+        }
+    }
+
+    threads
+        .join()
+        .unwrap();
+}