Adding leading newline to gem append_file string

[johnmdonahue]

Issue

The gem action appends to the Gemfile without inserting a leading newline which can break installers.

Steps to Reproduce

Create a TestApp:

$ rails new TestApp
$ cd TestApp/

Edit the Gemfile to add rails_admin to the bottom with no trailing line break:

.
.
gem 'rails_admin', :git => 'git://github.com/sferik/rails_admin.git'

Bundle and run rails_admin installer:

$ bundle install
$ rails g rails_admin:install

Results in the following edited Gemfile:

.
.
gem 'rails_admin', :git => 'git://github.com/sferik/rails_admin.git'gem "devise"

Which fails on generate devise:install:

generate  devise:install
/Users/username/.rvm/gems/ruby-1.9.3-head/gems/bundler-1.0.21/lib/bundler/dsl.rb:7:in `instance_eval': /Users/username/TestApp/Gemfile:38: syntax error, unexpected tIDENTIFIER, expecting $end (SyntaxError)
....com/sferik/rails_admin.git'gem "devise"

Solution

This appears to be a problem with the gem generator action, where
append_file is called with a trailing newline but not a leading one.

in_root do
  str = "gem #{parts.join(", ")}\n" # Problem here
  str = "  " + str if @in_group
  append_file "Gemfile", str, :verbose => false
end

Without getting tricky, it seems like it might make sense to add a leading newline here:

in_root do
  str = "\ngem #{parts.join(", ")}\n"
  str = "  " + str if @in_group
  append_file "Gemfile", str, :verbose => false
end

Thoughts?

[josevalim]

Looks good. We just need a test, thanks!

[bbenezech]

👍

[josevalim]

Sorry, just now I have realized that the authors of this pull request and #3752 (that got merged) were different. @ganeshkumar, the next time please include the original patch in your pull request so both authors gets commits in.

[johnmdonahue]

The test and fix on #3752 render a group block without indentation.

group :development, :test do

gem "rspec-rails"
end

I have updated my branch to handle gem groups as well as the leading newline complete with a test.

group :development, :test do

  gem "rspec-rails"
end

[sukeerthiadiga]

+1

[johnmdonahue]

I guess my question/concern here is that the modified test does not check for leading newline:

/^gem "rspec-rails"$/

Also the output for gem groups now has no indentation.

A better possible solution here that maintains existing linebreaks and indentation as well as actually testing for leading newline.