1 files changed, 91 insertions, 0 deletions
diff --git a/lib/bundler/injector.rb b/lib/bundler/injector.rb
new file mode 100644
index 0000000000..cba1b3d5e5
--- /dev/null
+++ b/lib/bundler/injector.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+module Bundler
+  class Injector
+    def self.inject(new_deps, options = {})
+      injector = new(new_deps, options)
+      injector.inject(Bundler.default_gemfile, Bundler.default_lockfile)
+    end
+
+    def initialize(new_deps, options = {})
+      @new_deps = new_deps
+      @options = options
+    end
+
+    def inject(gemfile_path, lockfile_path)
+      if Bundler.settings[:frozen]
+        # ensure the lock and Gemfile are synced
+        Bundler.definition.ensure_equivalent_gemfile_and_lockfile(true)
+        # temporarily remove frozen while we inject
+        frozen = Bundler.settings.delete(:frozen)
+      end
+
+      # evaluate the Gemfile we have now
+      builder = Dsl.new
+      builder.eval_gemfile(gemfile_path)
+
+      # don't inject any gems that are already in the Gemfile
+      @new_deps -= builder.dependencies
+
+      # add new deps to the end of the in-memory Gemfile
+      # Set conservative versioining to false because we want to let the resolver resolve the version first
+      builder.eval_gemfile("injected gems", build_gem_lines(false)) if @new_deps.any?
+
+      # resolve to see if the new deps broke anything
+      @definition = builder.to_definition(lockfile_path, {})
+      @definition.resolve_remotely!
+
+      # since nothing broke, we can add those gems to the gemfile
+      append_to(gemfile_path, build_gem_lines(@options[:conservative_versioning])) if @new_deps.any?
+
+      # since we resolved successfully, write out the lockfile
+      @definition.lock(Bundler.default_lockfile)
+
+      # return an array of the deps that we added
+      return @new_deps
+    ensure
+      Bundler.settings[:frozen] = "1" if frozen
+    end
+
+  private
+
+    def conservative_version(spec)
+      version = spec.version
+      return ">= 0" if version.nil?
+      segments = version.segments
+      seg_end_index = version >= Gem::Version.new("1.0") ? 1 : 2
+
+      prerelease_suffix = version.to_s.gsub(version.release.to_s, "") if version.prerelease?
+      "~> #{segments[0..seg_end_index].join(".")}#{prerelease_suffix}"
+    end
+
+    def build_gem_lines(conservative_versioning)
+      @new_deps.map do |d|
+        name = d.name.dump
+
+        requirement = if conservative_versioning
+          ", \"#{conservative_version(@definition.specs[d.name][0])}\""
+        else
+          ", #{d.requirement.as_list.map(&:dump).join(", ")}"
+        end
+
+        if d.groups != Array(:default)
+          group = d.groups.size == 1 ? ", :group => #{d.groups.inspect}" : ", :groups => #{d.groups.inspect}"
+        end
+
+        source = ", :source => \"#{d.source}\"" unless d.source.nil?
+
+        %(gem #{name}#{requirement}#{group}#{source})
+      end.join("\n")
+    end
+
+    def append_to(gemfile_path, new_gem_lines)
+      gemfile_path.open("a") do |f|
+        f.puts
+        if @options["timestamp"] || @options["timestamp"].nil?
+          f.puts "# Added at #{Time.now} by #{`whoami`.chomp}:"
+        end
+        f.puts new_gem_lines
+      end
+    end
+  end
+end