ruby: Add support for "rubocop" language server (#14661)

Hi, this pull request adds support for `rubocop` language server. I
noticed that `ruby-lsp` LS is becoming more popular but it still lacks
diagnostics support in Zed. To cover that missing feature, it could be
good to use `rubocop` LS to show diagnostics alongside with the running
Ruby LSP.

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

extensions/ruby/extension.toml

@@ -14,6 +14,10 @@ language = "Ruby"
 name = "Ruby LSP"
 language = "Ruby"
 
+[language_servers.rubocop]
+name = "Rubocop"
+language = "Ruby"
+
 [grammars.ruby]
 repository = "https://github.com/tree-sitter/tree-sitter-ruby"
 commit = "dc2d7d6b50f9975bc3c35bbec0ba11b2617b736b"

extensions/ruby/src/language_servers.rs

@@ -1,5 +1,7 @@
+mod rubocop;
 mod ruby_lsp;
 mod solargraph;
 
+pub use rubocop::*;
 pub use ruby_lsp::*;
 pub use solargraph::*;

extensions/ruby/src/language_servers/rubocop.rs

@@ -0,0 +1,19 @@
+use zed_extension_api::{self as zed, Result};
+
+pub struct Rubocop {}
+
+impl Rubocop {
+    pub const LANGUAGE_SERVER_ID: &'static str = "rubocop";
+
+    pub fn new() -> Self {
+        Self {}
+    }
+
+    pub fn server_script_path(&mut self, worktree: &zed::Worktree) -> Result<String> {
+        let path = worktree.which("rubocop").ok_or_else(|| {
+            "rubocop must be installed manually. Install it with `gem install rubocop` or specify the 'binary' path to it via local settings.".to_string()
+        })?;
+
+        Ok(path)
+    }
+}

extensions/ruby/src/ruby.rs

@@ -5,11 +5,12 @@ use zed::settings::LspSettings;
 use zed::{serde_json, CodeLabel, LanguageServerId};
 use zed_extension_api::{self as zed, Result};
 
-use crate::language_servers::{RubyLsp, Solargraph};
+use crate::language_servers::{Rubocop, RubyLsp, Solargraph};
 
 struct RubyExtension {
     solargraph: Option<Solargraph>,
     ruby_lsp: Option<RubyLsp>,
+    rubocop: Option<Rubocop>,
 }
 
 impl zed::Extension for RubyExtension {
@@ -17,6 +18,7 @@ impl zed::Extension for RubyExtension {
         Self {
             solargraph: None,
             ruby_lsp: None,
+            rubocop: None,
         }
     }
 
@@ -44,6 +46,15 @@ impl zed::Extension for RubyExtension {
                     env: worktree.shell_env(),
                 })
             }
+            Rubocop::LANGUAGE_SERVER_ID => {
+                let rubocop = self.rubocop.get_or_insert_with(|| Rubocop::new());
+
+                Ok(zed::Command {
+                    command: rubocop.server_script_path(worktree)?,
+                    args: vec!["--lsp".into()],
+                    env: worktree.shell_env(),
+                })
+            }
             language_server_id => Err(format!("unknown language server: {language_server_id}")),
         }
     }