Add minimal Scala support - tree-sitter, Metals

Adds

 - Scala syntax highlighting using `tree-sitter-scala`
 - basic Metals LSP support, without automatic installation

Most of the tree-sitter queries have been picked up and repurposed from
[tree-sitter-scala](https://github.com/tree-sitter/tree-sitter-scala) and
[nvim-treesitter](https://github.com/nvim-treesitter/nvim-treesitter/tree/master/queries/scala) projects.

Author: mprihoda

Cargo.lock

@@ -303,6 +303,7 @@ tree-sitter-python = "0.20.2"
 tree-sitter-racket = { git = "https://github.com/zed-industries/tree-sitter-racket", rev = "eb010cf2c674c6fd9a6316a84e28ef90190fe51a" }
 tree-sitter-ruby = "0.20.0"
 tree-sitter-rust = "0.20.3"
+tree-sitter-scala = { git = "https://github.com/tree-sitter/tree-sitter-scala.git", rev = "45b5ba0e749a8477a8fd2666f082f352859bdc3c" }
 tree-sitter-scheme = { git = "https://github.com/6cdh/tree-sitter-scheme", rev = "af0fd1fa452cb2562dc7b5c8a8c55551c39273b9" }
 tree-sitter-svelte = { git = "https://github.com/Himujjal/tree-sitter-svelte", rev = "bd60db7d3d06f89b6ec3b287c9a6e9190b5564bd" }
 tree-sitter-toml = { git = "https://github.com/tree-sitter/tree-sitter-toml", rev = "342d9be207c2dba869b9967124c679b5e6fd0ebe" }

Cargo.toml

@@ -72,6 +72,7 @@ tree-sitter-python.workspace = true
 tree-sitter-racket.workspace = true
 tree-sitter-ruby.workspace = true
 tree-sitter-rust.workspace = true
+tree-sitter-scala.workspace = true
 tree-sitter-scheme.workspace = true
 tree-sitter-svelte.workspace = true
 tree-sitter-toml.workspace = true

crates/languages/Cargo.toml

@@ -34,6 +34,7 @@ mod purescript;
 mod python;
 mod ruby;
 mod rust;
+mod scala;
 mod svelte;
 mod tailwind;
 mod terraform;
@@ -109,6 +110,7 @@ pub fn init(
         ("racket", tree_sitter_racket::language()),
         ("ruby", tree_sitter_ruby::language()),
         ("rust", tree_sitter_rust::language()),
+        ("scala", tree_sitter_scala::language()),
         ("scheme", tree_sitter_scheme::language()),
         ("svelte", tree_sitter_svelte::language()),
         ("toml", tree_sitter_toml::language()),
@@ -359,6 +361,7 @@ pub fn init(
         ))]
     );
     language!("dart", vec![Arc::new(dart::DartLanguageServer {})]);
+    language!("scala", vec![Arc::new(scala::MetalsLspAdapter {})]);
 }
 
 #[cfg(any(test, feature = "test-support"))]

crates/languages/src/lib.rs

@@ -0,0 +1,58 @@
+use anyhow::{anyhow, Result};
+use async_trait::async_trait;
+pub use language::*;
+use lsp::LanguageServerBinary;
+use std::{any::Any, path::PathBuf};
+
+pub struct MetalsLspAdapter;
+
+#[async_trait]
+impl LspAdapter for MetalsLspAdapter {
+    fn name(&self) -> LanguageServerName {
+        LanguageServerName("metals".into())
+    }
+
+    async fn fetch_latest_server_version(
+        &self,
+        _: &dyn LspAdapterDelegate,
+    ) -> Result<Box<dyn 'static + Any + Send>> {
+        Ok(Box::new(()))
+    }
+
+    async fn fetch_server_binary(
+        &self,
+        _version: Box<dyn 'static + Send + Any>,
+        _container_dir: PathBuf,
+        _: &dyn LspAdapterDelegate,
+    ) -> Result<LanguageServerBinary> {
+        Err(anyhow!(
+            "metals must be installed and available in your $PATH"
+        ))
+    }
+
+    async fn cached_server_binary(
+        &self,
+        _: PathBuf,
+        _: &dyn LspAdapterDelegate,
+    ) -> Option<LanguageServerBinary> {
+        Some(LanguageServerBinary {
+            path: "metals".into(),
+            env: None,
+            arguments: vec![],
+        })
+    }
+
+    fn can_be_reinstalled(&self) -> bool {
+        false
+    }
+
+    async fn installation_test_binary(
+        &self,
+        _container_dir: PathBuf,
+    ) -> Option<LanguageServerBinary> {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {}

crates/languages/src/scala.rs

@@ -0,0 +1,3 @@
+("(" @open ")" @close)
+("[" @open "]" @close)
+("{" @open "}" @close)

crates/languages/src/scala/brackets.scm

@@ -0,0 +1,15 @@
+name = "Scala"
+grammar = "scala"
+path_suffixes = ["scala", "sbt", "sc"]
+line_comments = ["// "]
+autoclose_before = ";:.,=}])"
+brackets = [
+{ start = "{", end = "}", close = true, newline = true },
+{ start = "[", end = "]", close = true, newline = true },
+{ start = "(", end = ")", close = true, newline = true },
+{ start = "\"", end = "\"", close = true, newline = false, not_in = ["comment", "string"] },
+{ start = "'", end = "'", close = true, newline = false, not_in = ["comment", "string"] },
+{ start = "`", end = "`", close = true, newline = false, not_in = ["comment", "string"] },
+{ start = "/*", end = " */", close = true, newline = false, not_in = ["comment", "string"] }
+]
+collapsed_placeholder = " /* ... */ "