Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

When pattern includes odd number of single quotes, the generated Ruby client code contains syntax errors.

openapi-generator version

$ java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar version
4.0.0-SNAPSHOT

$ git log --oneline -n 1
0b66fa5c82 (HEAD -> master, origin/master, origin/HEAD) add servers to path, operation (#2048)

OpenAPI declaration file content or url

See: https://gist.github.com/autopp/e707d5d2ec36f7cfe6a3950d76d54b6f#file-swagger-yml

The point to notice in this example is that ' is included in the pattern constraint of the property y of the model x.

Command line used for generation

$ java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate --skip-validate-spec -g ruby -o /tmp/gem -i 'https://gist.githubusercontent.com/autopp/e707d5d2ec36f7cfe6a3950d76d54b6f/raw/0ca732fa77402c3dcbb735e41eb5f6e5bc58462d/swagger.yml'

Steps to reproduce

1. Run the above command to generate client code for Ruby.
2. Run ruby -c /tmp/gem/lib/openapi_client/models/x.rb to check syntax of the generated model code.
3. Get errors in lib/openapi_client/models/x.rb:

   /tmp/gem/lib/openapi_client/models/x.rb:51: syntax error, unexpected '.'
   ...ust conform to the pattern /'/.')
   ...                              ^
   /tmp/gem/lib/openapi_client/models/x.rb:60: syntax error, unexpected ')'
   ...y.nil? && @y !~ Regexp.new(/'/)
   ...                              ^
   /tmp/gem/lib/openapi_client/models/x.rb:68: syntax error, unexpected '.'
   ...ust conform to the pattern /'/.'
   ...                              ^
   /tmp/gem/lib/openapi_client/models/x.rb:206: unterminated string meets end of file
   /tmp/gem/lib/openapi_client/models/x.rb:206: syntax error, unexpected end-of-input, expecting keyword_end
   

Related issues/PRs

#2067

Suggest a fix

escapeText of RubyClientCodegen seems to escape for double-quote string literals only. However, the corresponding template uses a single quote string.
I think it is difficult for the generator to determine whether the expansion destination is a single-quote string or a double-quote string. Instead, I think that it is better to unify it with a double-quote string in the template.