Add cop to prevent accidental writing to stdout

.rubocop.yml

@@ -6,6 +6,7 @@ require:
   - rubocop-md
   - rubocop-minitest
   - rubocop-rake
+  - ./lib/rubocop/cop/ruby_lsp/output
   - ./lib/rubocop/cop/ruby_lsp/use_language_server_aliases
   - ./lib/rubocop/cop/ruby_lsp/use_register_with_handler_method
 
@@ -33,6 +34,10 @@ RubyLsp/UseLanguageServerAliases:
   Exclude:
     - "test/**/*.rb"
 
+RubyLsp/Output:
+  Include:
+    - "**/*.rb"
+
 Sorbet/FalseSigil:
   Enabled: false
 
@@ -60,6 +65,7 @@ Sorbet/StrictSigil:
     - "lib/ruby_indexer/lib/ruby_indexer/prefix_tree.rb"
     - "lib/ruby_lsp/load_sorbet.rb"
     - "lib/ruby_lsp/scripts/compose_bundle.rb"
+    - "lib/rubocop/cop/ruby_lsp/output.rb"
 
 Layout/ClassStructure:
   Enabled: true

lib/rubocop/cop/ruby_lsp/output.rb

@@ -0,0 +1,68 @@
+# typed: false
+# frozen_string_literal: true
+
+require "rubocop"
+require "sorbet-runtime"
+
+module RuboCop
+  module Cop
+    module RubyLsp
+      class Output < Base
+        include RangeHelp
+
+        MSG = "Do not write to stdout as it can break the LSP communication. " \
+          "Remove it, or use `Notification.window_log_message` instead."
+        RESTRICT_ON_SEND = [
+          :ap,
+          :p,
+          :pp,
+          :pretty_print,
+          :print,
+          :puts,
+          :binwrite,
+          :syswrite,
+          :write,
+          :write_nonblock,
+        ].freeze
+        ALLOWED_TYPES = [:send, :csend, :block, :numblock].freeze
+
+        def_node_matcher :output?, <<~PATTERN
+          (send nil? {:ap :p :pp :pretty_print :print :puts} ...)
+        PATTERN
+
+        def_node_matcher :io_output?, <<~PATTERN
+          (send
+            {
+              (gvar #match_gvar?)
+              (const {nil? cbase} {:STDOUT :STDERR})
+            }
+            {:binwrite :syswrite :write :write_nonblock}
+            ...)
+        PATTERN
+
+        def on_send(node)
+          return if ALLOWED_TYPES.include?(node.parent&.type)
+          return if !output?(node) && !io_output?(node)
+
+          range = offense_range(node)
+
+          add_offense(range)
+        end
+
+        private
+
+        def match_gvar?(sym)
+          [:$stdout, :$stderr].include?(sym)
+        end
+
+        def offense_range(node)
+          if node.receiver
+            range_between(node.source_range.begin_pos, node.loc.selector.end_pos)
+          else
+            node.loc.selector
+          end
+        end
+      end
+    end
+  end
+end

project-words

@@ -6,17 +6,20 @@ bigdecimal
 bindir
 binmode
 binread
+binstub
+binwrite
 Bizt
 Bizw
 bufnr
-binstub
 bytesize
 byteslice
+cbase
 codepoint
 codepoints
 concats
 copen
 Corge
+csend
 dont
 eglot
 Eglot
@@ -28,6 +31,7 @@ Floo
 fnmatch
 fooo
 gemname
+gvar
 hostedtoolcache
 importmap
 indexables
@@ -50,14 +54,16 @@ mkpath
 multibyte
 nargs
 nodoc
+nonblock
 noreturn
+numblock
 nvim
 popen
+qorge
 qtlzwssomeking
 quickfixes
-quxx
 quux
-qorge
+quxx
 rdbg
 readlines
 realpath
@@ -83,6 +89,7 @@ strscan
 subexpression
 supertypes
 suppo
+syswrite
 unaliased
 unindexed
 unparser