Disable diagnostics on large files

lib/ruby_lsp/document.rb

@@ -16,6 +16,10 @@ class LanguageId < T::Enum
     extend T::Generic
 
     ParseResultType = type_member
+
+    # This maximum number of characters for providing expensive features, like semantic highlighting and diagnostics.
+    # This is the same number used by the TypeScript extension in VS Code
+    MAXIMUM_CHARACTERS_FOR_EXPENSIVE_FEATURES = 100_000
     EMPTY_CACHE = T.let(Object.new.freeze, Object)
 
     abstract!
@@ -113,6 +117,11 @@ def create_scanner
       Scanner.new(@source, @encoding)
     end
 
+    sig { returns(T::Boolean) }
+    def past_expensive_limit?
+      @source.length > MAXIMUM_CHARACTERS_FOR_EXPENSIVE_FEATURES
+    end
+
     class Scanner
       extend T::Sig
 

lib/ruby_lsp/requests/diagnostics.rb

@@ -46,7 +46,9 @@ def perform
         diagnostics.concat(syntax_error_diagnostics, syntax_warning_diagnostics)
 
         # Running RuboCop is slow, so to avoid excessive runs we only do so if the file is syntactically valid
-        return diagnostics if @document.syntax_error? || @active_linters.empty?
+        if @document.syntax_error? || @active_linters.empty? || @document.past_expensive_limit?
+          return diagnostics
+        end
 
         @active_linters.each do |linter|
           linter_diagnostics = linter.run_diagnostic(@uri, @document)

lib/ruby_lsp/requests/semantic_highlighting.rb

@@ -33,10 +33,6 @@ module Requests
     class SemanticHighlighting < Request
       extend T::Sig
 
-      # This maximum number of characters for providing highlighting is the same limit imposed by the VS Code TypeScript
-      # extension. Even with delta requests, anything above this number lags the editor significantly
-      MAXIMUM_CHARACTERS_FOR_HIGHLIGHT = 100_000
-
       class << self
         extend T::Sig
 

lib/ruby_lsp/server.rb

@@ -315,13 +315,14 @@ def text_document_did_open(message)
           language_id: language_id,
         )
 
-        if document.source.length > Requests::SemanticHighlighting::MAXIMUM_CHARACTERS_FOR_HIGHLIGHT
+        if document.past_expensive_limit?
           send_message(
             Notification.new(
               method: "window/showMessage",
               params: Interface::ShowMessageParams.new(
                 type: Constant::MessageType::WARNING,
-                message: "This file is too long. For performance reasons, semantic highlighting will be disabled",
+                message: "This file is too long. For performance reasons, semantic highlighting and " \
+                  "diagnostics will be disabled",
               ),
             ),
           )
@@ -427,7 +428,7 @@ def run_combined_requests(message)
     def text_document_semantic_tokens_full(message)
       document = @store.get(message.dig(:params, :textDocument, :uri))
 
-      if document.source.length > Requests::SemanticHighlighting::MAXIMUM_CHARACTERS_FOR_HIGHLIGHT
+      if document.past_expensive_limit?
         send_empty_response(message[:id])
         return
       end
@@ -448,7 +449,7 @@ def text_document_semantic_tokens_full(message)
     def text_document_semantic_tokens_delta(message)
       document = @store.get(message.dig(:params, :textDocument, :uri))
 
-      if document.source.length > Requests::SemanticHighlighting::MAXIMUM_CHARACTERS_FOR_HIGHLIGHT
+      if document.past_expensive_limit?
         send_empty_response(message[:id])
         return
       end
@@ -476,7 +477,7 @@ def text_document_semantic_tokens_range(message)
       uri = params.dig(:textDocument, :uri)
       document = @store.get(uri)
 
-      if document.source.length > Requests::SemanticHighlighting::MAXIMUM_CHARACTERS_FOR_HIGHLIGHT
+      if document.past_expensive_limit?
         send_empty_response(message[:id])
         return
       end