From d6bebcd248a2822177b9d14e99dd47e294b9b3df Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Tue, 1 Oct 2019 12:44:31 +0200
Subject: [PATCH] Fix Ruby 2.7 compatibility in GenericService.underscore

---
 src/ruby/lib/grpc/generic/service.rb  | 1 +
 src/ruby/spec/generic/service_spec.rb | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/src/ruby/lib/grpc/generic/service.rb b/src/ruby/lib/grpc/generic/service.rb
index 169a62f11d3..399d0355c8a 100644
--- a/src/ruby/lib/grpc/generic/service.rb
+++ b/src/ruby/lib/grpc/generic/service.rb
@@ -31,6 +31,7 @@ module GRPC
     #
     # @param s [String] the string to be converted.
     def self.underscore(s)
+      s = +s # Avoid mutating the argument, as it might be frozen.
       s.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
       s.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
       s.tr!('-', '_')
diff --git a/src/ruby/spec/generic/service_spec.rb b/src/ruby/spec/generic/service_spec.rb
index 57aec89ce51..16f8783152e 100644
--- a/src/ruby/spec/generic/service_spec.rb
+++ b/src/ruby/spec/generic/service_spec.rb
@@ -55,6 +55,8 @@ describe GenericService do
       expect(GenericService.underscore('AMethod')).to eq('a_method')
       expect(GenericService.underscore('PrintHTML')).to eq('print_html')
       expect(GenericService.underscore('SeeHTMLBooks')).to eq('see_html_books')
+
+      expect(GenericService.underscore('SeeHTMLBooks'.freeze)).to eq('see_html_books')
     end
   end