change sql_state to attr_reader to avoid ruby warning

[seuros]

this patch will remove this warning

mysql2-0.3.16/lib/mysql2/error.rb:22: warning: method redefined; discarding old sql_state=

[sodabrew]

Oh, interesting issue. I always took attr_reader as a hint that the value was read-only. I hope there aren't implementations of Ruby that take it to mean that way and get upset about the writer method?

[seuros]

attr_reader just define the getter , attr_writer define the setter, and attr_accesor define both.

[simi]

What's your used Ruby implementation, version and are you using any of those options?

  -v, --verbose   print version number, then turn on verbose mode
  -w              turn warnings on for your script
  -W[level=2]     set warning level; 0=silence, 1=medium, 2=verbose

[seuros]

Any ruby implementation . https://travis-ci.org/rails/rails/jobs/35231944
I was thinking in changing the error class implementation like #545, but that will be a breaking change which nobody want for now.

[simi]

Ahh, you mean this:

/home/travis/.rvm/rubies/ruby-1.9.3-p547/bin/ruby -w -Itest test/cases/disconnected_test.rb
/home/travis/.rvm/gems/ruby-1.9.3-p547/gems/bundler-1.7.2/lib/bundler/definition.rb:391: warning: private attribute?
/home/travis/.rvm/gems/ruby-1.9.3-p547/gems/bundler-1.7.2/lib/bundler/index.rb:110: warning: `*' interpreted as argument prefix
/home/travis/build/rails/rails/vendor/bundle/ruby/1.9.1/gems/minitest-5.3.3/lib/minitest.rb:46: warning: (...) interpreted as grouped expression
Using mysql2
/home/travis/build/rails/rails/vendor/bundle/ruby/1.9.1/gems/mysql2-0.3.16/lib/mysql2/error.rb:22: warning: method redefined; discarding old sql_state=
Run options: --seed 13616

ruby -w

[simi]

The question is: Should be mysql2 warning proof?

@brianmario @sodabrew

[seuros]

@simi , Why it shouldn't ?

[sodabrew]

As much as possible, IMHO. Warnings are usually there for a reason.

@seuros I don't think #545 is a problematic change, because the arguments are very new. server_version was added in 271ea5e in January 2014 for version 0.3.15.

[seuros]

I don't know, when i changed it some of the gems i monitor broke. I don't remember which one, but i had the exact implementation.