Add custom command to return LSP internal state

lib/ruby_lsp/base_server.rb

@@ -90,7 +90,8 @@ def start
         # The following requests need to be executed in the main thread directly to avoid concurrency issues. Everything
         # else is pushed into the incoming queue
         case method
-        when "initialize", "initialized", "textDocument/didOpen", "textDocument/didClose", "textDocument/didChange"
+        when "initialize", "initialized", "textDocument/didOpen", "textDocument/didClose", "textDocument/didChange",
+          "rubyLsp/diagnoseState"
           process_message(message)
         when "shutdown"
           @global_state.synchronize do

lib/ruby_lsp/server.rb

@@ -108,6 +108,8 @@ def process_message(message)
         )
       when "rubyLsp/composeBundle"
         compose_bundle(message)
+      when "rubyLsp/diagnoseState"
+        diagnose_state(message)
       when "$/cancelRequest"
         @global_state.synchronize { @cancelled_requests << message[:params][:id] }
       when nil
@@ -1368,5 +1370,24 @@ def compose_bundle(message)
         end
       end
     end
+
+    # Returns internal state information for debugging purposes
+    sig { params(message: T::Hash[Symbol, T.untyped]).void }
+    def diagnose_state(message)
+      documents = {}
+      @store.each { |uri, document| documents[uri] = document.source }
+
+      send_message(
+        Result.new(
+          id: message[:id],
+          response: {
+            workerAlive: @worker.alive?,
+            backtrace: @worker.backtrace,
+            documents: documents,
+            incomingQueueSize: @incoming_queue.length,
+          },
+        ),
+      )
+    end
   end
 end

test/server_test.rb

@@ -1371,6 +1371,31 @@ class Foo
     end
   end
 
+  def test_diagnose_state
+    @server.process_message({
+      method: "textDocument/didOpen",
+      params: {
+        textDocument: {
+          uri: URI::Generic.from_path(path: "/foo.rb"),
+          text: "class Foo\nend",
+          version: 1,
+          languageId: "ruby",
+        },
+      },
+    })
+    @server.process_message({ id: 1, method: "rubyLsp/diagnoseState", params: {} })
+    result = find_message(RubyLsp::Result, id: 1)
+
+    assert(result.response[:workerAlive])
+    assert_equal({ "file:///foo.rb" => "class Foo\nend" }, result.response[:documents])
+
+    first, second = result.response[:backtrace]
+    assert_match(/<internal:thread_sync>.*Thread::Queue#pop/, first)
+    assert_match(/base_server\.rb.*RubyLsp::BaseServer#new_worker/, second)
+
+    assert_equal(0, result.response[:incomingQueueSize])
+  end
+
   private
 
   def with_uninstalled_rubocop(&block)