Allow arbitrary setup code to be inserted into binstub

[merhard]

This commit is designed to be the first step to solving this issue.

The pull request would allow the spring-commands-rspec gem to be changed to:

# lib/spring/commands/rspec.rb

module Spring
  module Commands
    class RSpec
      def env(*)
        "test"
      end

      def exec_name
        "rspec"
      end

      def gem_name
        "rspec-core"
      end

      def binstub_code
        "RSpec.configuration.start_time = Time.now"
      end
    end

    Spring.register_command "rspec", RSpec.new
    Spring::Commands::Rake.environment_matchers[/^spec($|:)/] = "test"
  end
end

The generated rspec binstub would then be:

#!/usr/bin/env ruby
begin
  load File.expand_path("../spring", __FILE__)
rescue LoadError
end
RSpec.configuration.start_time = Time.now
require 'bundler/setup'
load Gem.bin_path('rspec-core', 'rspec')

[jeremy]

How about command.binstub_code + "\n"? - no worries about an extra newline

[jeremy]

Actually, better to handle this when the binstub is written anyway. Introduce a \n there.

[merhard]

So basically revert 0b46807 and only have 3d5653e?

I added the optional newline code because of a failed test (AppTest#test_binstub_upgrade [../test/acceptance/app_test.rb:224]). I'll make the changes and fix the failing test.

[merhard]

@jeremy - How's this?

[jeremy]

@merhard - Cool. Considering this is a shim that needs to run only when the executable is sprung, consider giving binstub_code a more precise name and putting it in the loader code:

begin
  load File.expand_path("../spring", __FILE__)
rescue LoadError
  # command's post-spring shim doesn't load if spring isn't in use
else
  <command's post-spring shim>
end

[merhard]

@jeremy - I renamed binstub_code to runner_setup_code as it is setup code for spring's rspec runner. I also moved the shim into the loader code.

[jeremy]

@merhard Nice. runner_setup_code describes the code you're injecting rather than the disposition of the code in the binstub, though. Consider something like binstub_prelude, indicating that it's code that before the original binstub.

[merhard]

@jeremy How's this? I can squash the commits if there isn't anything else.

[jeremy]

What's the story with the trailing NUL byte?

[merhard]

@jeremy It isn't a NUL byte. '\0' or "\\0" in the replacement string of #sub inserts the match from the regexp into the resulting string. I first saw it in thor. It is also in the "Search And Replace" section of this site. Perhaps replacing "\\0" with "end" would be better?

[jeremy]

Oh cool! Double backslash. That's cool - but yeah, end would be clearer 😁

[merhard]

@jeremy changed

[jeremy]

@merhard Super! Squash?

[merhard]

@jeremy squashed

[jeremy]

👍

[merhard]

thanks

[jonleighton]

Was this change specifically aimed at fixing the rspec issue or was some more general use case envisaged?

[merhard]

It is designed to be used by any spring-commands-* gem to add code to the binstub. I had the rspec issue in mind when writing this code, but any spring command can use it.

[jonleighton]

Sure, I realise that it can be used by any command, however I'm dubious about whether we actually need this feature, hence I wanted to see if there were other reasons to add it. (For others: I suggested an alternative fix to the rspec issue at jonleighton/spring-commands-rspec#20 (comment))