[gem install] installs multipe platforms

[abaumgaertner]

it is possible to install a gem for multiple platforms.
gems that have been build with devkit use --platform=ruby (devkit platform is x64-mingw32)
when you run gem install (or bundle install) the gem is installed again - with specific platform binaries: x64-mingw32

see https://bugs.ruby-lang.org/issues/10919 for full details.

[tenderlove]

Thanks for the report. I'm not sure what to do about this.

solution a:
gem install should not install an additional platform, if the gem is already present

This is a tough one. Doing a gem install will always install the gem, even if it's the same platform. For example doing gem install foo on Linux will install the foo gem twice. It doesn't care that foo was already installed. I think this would be a large change.

gem list should always display the platform (not only if there are more than 1)

I could get behind this.

solution b:
add an option to gem install that forces devkit build for specific platform so gem install will recognize that the platform is already present.

I think the "ruby" platform generally means that the gem was not precompiled for a particular platform. Where "java" means the gem was precompiled for JRuby, "x64-mingw32" for windows, etc. It seems possible to tag a gem with a platform on install, but since you actually installed the gem from source, that doesn't seem to make sense.

IMO, gem install is working as advertised. When you did gem install --platform=ruby, you got what you asked for: the gem with the Ruby platform. Since we implicitly default the platform on windows, the second gem install also fetched the platform it was supposed to.

Is this causing a bug?

[abaumgaertner]

thanks for the infos ...

the initial issue, gems can only be compiled with devkit when using --platform=ruby
gem install --platform=x64-mingw32 will download and install the gem with packaged binary and not compile the gem with devkit for this platform - changing this behavior doesn't make sense - in my example mysql2, there is some additonal code in the x64-mingw32 gem to determine the current ruby version and dynamically require the correct .so for it

the 2nd issue - ruby require does not support multiple platforms (which makes sense, since you would expect really only one) why would i have a gem with two platforms ruby and x64-mingw32 installed? ruby require prefers the ruby platform over the x64-mingw32. IMO - this should be the basis for a solution. see my test below (both platforms installed - require uses ruby)

Since we implicitly default the platform on windows, the second gem install also fetched the platform it was supposed to.

EDIT:
on ruby <= 2.1 - gem install mysql2 on windows does not default to mysql2-x64-mingw32 but will install mysql2 (platform=ruby)
on ruby >= 2.2 windows defaults to x64-mingw32

suggested solution:
if platform ruby is installed, installation of additional platforms doesn't make sense (since ruby is ignoring them in require anyway) - throw at least a warning during installation
if other platform is present and ruby platform is installed, throw a warning that the existing platform will be ignored

some addtional info
the build for mysql2 --platform=ruby worked - running bundle install (e.g. redmine) will install also the mysql2-0.3.18-x64-mingw32.gem
I'll open issue for that with bundler.

for e.g. mysql2 - it leads to this problem - there is no .so for ruby 2.2 yet - see below
ruby seems to take the platform ruby first - the require tests works after both versions have been installed (ruby supercedes x64-mingw32). I've also tested this with ruby 2.1.5 (mysql2-0.3.18-x64-mingw32 has a working binary for ruby 2.1)

this installs
gem install mysql2 -N --platform=x64-mingw32 -- "--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64"
this compiles
gem install mysql2 -N --platform=ruby -- "--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64"

C:\apps\redmine_dev\bin>gem install mysql2
Fetching: mysql2-0.3.18-x64-mingw32.gem (100%)

======================================================================================================

 \ You've installed the binary version of mysql2.
  It was built using MySQL Connector/C version 6.1.5.
  It's recommended to use the exact same version to avoid potential issues.

  At the time of building this gem, the necessary DLL files were retrieved from:
  http://cdn.mysql.com/Downloads/Connector-C/mysql-connector-c-6.1.5-winx64.zip

 \ This gem *includes* vendor/libmysql.dll with redistribution notice in vendor/README.

======================================================================================================

Successfully installed mysql2-0.3.18-x64-mingw32
Parsing documentation for mysql2-0.3.18-x64-mingw32
Installing ri documentation for mysql2-0.3.18-x64-mingw32
Done installing documentation for mysql2 after 0 seconds
1 gem installed

C:\apps\redmine_dev\bin>more ..\test\mysql.rb
require 'mysql2'

C:\apps\redmine_dev\bin>ruby -v
ruby 2.2.2p86 (2015-03-03 revision 49825) [x64-mingw32]

C:\apps\redmine_dev\bin>ruby ..\test\mysql.rb
C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- mysql2/2.2/mysql2 (LoadError)
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2/mysql2.rb:2:in `<top (required)>'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in `<top (required)>'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:128:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:128:in `rescue in require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:39:in `require'
        from ../test/mysql.rb:1:in `<main>'

C:\apps\redmine_dev\bin>gem install mysql2 -N --platform=ruby -- "--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64"
Fetching: mysql2-0.3.18.gem (100%)
Temporarily enhancing PATH to include DevKit...
Building native extensions with: '--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64'
This could take a while...
Successfully installed mysql2-0.3.18
1 gem installed

C:\apps\redmine_dev\bin>ruby ..\test\mysql.rb

C:\apps\redmine_dev\bin>gem list

*** LOCAL GEMS ***

bigdecimal (1.2.6)
bundle (0.0.1)
bundler (1.8.3)
ffi (1.9.6)
io-console (0.4.3)
json (1.8.1)
mini_portile (0.6.2)
mysql2 (0.3.18 ruby x64-mingw32)
psych (2.0.8)
puma (2.11.1)
rack (1.6.0)
rake (10.4.2)
rdoc (4.2.0)
rmagick (2.13.4)

C:\apps\redmine_dev\bin>

[tenderlove]

this is is not what happens - gem install mysql2 on windows does not default to mysql2-x64-mingw32 but will install mysql2 (platform=ruby)

That's not what your report on ruby-lang says. I will quote you below:

here comes the acutal issue:
rerun (also with other dependency managers e.g. bundle install) installs dupplicate gem for platform x64-mingw32

C:\apps\redmine_dev\bin>gem install mysql2
Fetching: mysql2-0.3.18-x64-mingw32.gem (100%)

======================================================================================================

 \ You've installed the binary version of mysql2.
  It was built using MySQL Connector/C version 6.1.5.
  It's recommended to use the exact same version to avoid potential issues.

  At the time of building this gem, the necessary DLL files were retrieved from:
  http://cdn.mysql.com/Downloads/Connector-C/mysql-connector-c-6.1.5-winx64.zip

 \ This gem *includes* vendor/libmysql.dll with redistribution notice in vendor/README.

======================================================================================================

Successfully installed mysql2-0.3.18-x64-mingw32
Parsing documentation for mysql2-0.3.18-x64-mingw32
Installing ri documentation for mysql2-0.3.18-x64-mingw32
Done installing documentation for mysql2 after 0 seconds
1 gem installed

gem install mysql2 did exactly what you asked it to do. You first installed the gem using the dev kit with the ruby platform, then you asked it to install mysql2 with an implicit platform of x64-mingw32.

[abaumgaertner]

sorry my mistake - you should not keep 2 shells with seperate ruby envs open
gem install mysql2 on
ruby 2.1 installs mysql2 with platform ruby
ruby 2.2 installs mysql2 x64-mingw32

retested with a fresh install - wrong again
platform x64-mingw32 has precedence over platform ruby
I'm not sure how to proceed.

workaround - manually uninstall x64-mingw32

C:\apps\redmine_dev\test>ruby -v
ruby 2.2.2p86 (2015-03-03 revision 49825) [x64-mingw32]

C:\apps\redmine_dev\test>ruby mysql.rb
C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- mysql2 (LoadError)
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from mysql.rb:1:in `<main>'

C:\apps\redmine_dev\test>ruby mysql.rb
C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- mysql2 (LoadError)
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from mysql.rb:1:in `<main>'

C:\apps\redmine_dev\test>gem install mysql2 -N --platform=ruby -- "--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64"
Fetching: mysql2-0.3.18.gem (100%)
Building native extensions with: '--with-mysql-dir=c:/apps/redmine_dev/mysql-5.6.23-winx64'
This could take a while...
Successfully installed mysql2-0.3.18
1 gem installed

C:\apps\redmine_dev\test>ruby mysql.rb

C:\apps\redmine_dev\test>gem install mysql2 -N
Fetching: mysql2-0.3.18-x64-mingw32.gem (100%)

======================================================================================================

 \ You've installed the binary version of mysql2.
  It was built using MySQL Connector/C version 6.1.5.
  It's recommended to use the exact same version to avoid potential issues.

  At the time of building this gem, the necessary DLL files were retrieved from:
  http://cdn.mysql.com/Downloads/Connector-C/mysql-connector-c-6.1.5-winx64.zip

 \ This gem *includes* vendor/libmysql.dll with redistribution notice in vendor/README.

======================================================================================================

Successfully installed mysql2-0.3.18-x64-mingw32
1 gem installed

C:\apps\redmine_dev\test>ruby mysql.rb
C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- mysql2/2.2/mysql2 (LoadError)
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2/mysql2.rb:2:in `<top (required)>'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in `<top (required)>'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:128:in `require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:128:in `rescue in require'
        from C:/apps/redmine_dev/ruby/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:39:in `require'
        from mysql.rb:1:in `<main>'

C:\apps\redmine_dev\test>gem uninstall mysql2

Select gem to uninstall:
 1. mysql2-0.3.18
 2. mysql2-0.3.18-x64-mingw32
 3. All versions
> 2
Successfully uninstalled mysql2-0.3.18-x64-mingw32

C:\apps\redmine_dev\test>gem list

*** LOCAL GEMS ***

bigdecimal (1.2.6)
io-console (0.4.3)
json (1.8.1)
mysql2 (0.3.18)
psych (2.0.8)
rake (10.4.2)
rdoc (4.2.0)

C:\apps\redmine_dev\test>ruby mysql.rb

C:\apps\redmine_dev\test>