Auto merge of #6279 - deivid-rodriguez:fix/encoding_bug, r=indirect

Fix hang when gemspec has incompatible encoding

### What was the end-user problem that led to this PR?

The problem was that if a gemspec had a non ascii character on it, and the external encoding is not utf-8, bundler would fail with a very cryptic error. CircleCI is very likely to reproduce this bug since its base images default to `LANG=C`. See [here](https://circleci.com/gh/deivid-rodriguez/pry-byebug/12) for an example.

In bundler's master, `bundle install` seems to hang in this same situation. I have no idea why but CPU usage goes crazy (100%) when running something like `LANG=C bundle install` with such a gemspec.

Note that adding a utf-8 magic encoding comment seems to fix the problem, but I think `bundler` should just work in this situation, or at least give the user a more helpful error message. And of course never hang either.

### What was your diagnosis of the problem?

My diagnosis was that bundler was reading an incompatible character from the gemspec and was not able to deal with it, nor give a useful error message.

### What is your fix for the problem, implemented in this PR?

My fix initial fix was to at least give a better error message, preventing the method building the error message itself from blowing up due to incompatible encodings. This is the initial patch that I wrote to improve the error message:

```diff
diff --git a/lib/bundler/dsl.rb b/lib/bundler/dsl.rb
index 37bfe3674..79ef563d1 100644
--- a/lib/bundler/dsl.rb
+++ b/lib/bundler/dsl.rb
@@ -581,7 +581,14 @@ The :#{name} git source is deprecated, and will be removed in Bundler 2.0.

       def parse_line_number_from_description
         description = self.description
-        if dsl_path && description =~ /((#{Regexp.quote File.expand_path(dsl_path)}|#{Regexp.quote dsl_path.to_s}):\d+)/
+        return [nil, description] unless dsl_path
+
+        quoted_expanded_dsl_path = Regexp.quote(File.expand_path(dsl_path))
+        quoted_dsl_path = Regexp.quote(dsl_path.to_s)
+
+        return [nil, description] unless Encoding.compatible?(quoted_dsl_path, description) && Encoding.compatible?(quoted_expanded_dsl_path, description)
+
+        if description =~ /((#{quoted_expanded_dsl_path}|#{quoted_dsl_path}):\d+)/
           trace_line = Regexp.last_match[1]
           description = description.sub(/#{Regexp.quote trace_line}:\s*/, "").sub("\n", " - ")
         end
```

With that patch, the error would be more clear, pointing at the exact line in the gemspec where the incompatible character was found.

However, after that I considered that maybe bundler doesn't need to read the gemspec as a text file, but could read it "binarily". That seemed to fix the problem indeed and made the `bundle install` succeed in this situation.

### Why did you choose this fix out of the possible options?

I chose this fix because not only fixes the error message but also seems to make `bundler` just work.

2 files changed, 18 insertions, 1 deletions

diff --git a/lib/bundler.rb b/lib/bundler.rb
index 63ae335ac6..8fc8da6dcb 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -441,7 +441,7 @@ EOF
 
     def load_gemspec_uncached(file, validate = false)
       path = Pathname.new(file)
-      contents = path.read
+      contents = read_file(file)
       spec = if contents.start_with?("---") # YAML header
         eval_yaml_gemspec(path, contents)
       else
diff --git a/spec/install/gemspecs_spec.rb b/spec/install/gemspecs_spec.rb
index 0c1ed99097..5dca6f68c0 100644
--- a/spec/install/gemspecs_spec.rb
+++ b/spec/install/gemspecs_spec.rb
@@ -46,6 +46,23 @@ RSpec.describe "bundle install" do
     expect(the_bundle).to include_gems "activesupport 2.3.2"
   end
 
+  it "does not hang when gemspec has incompatible encoding" do
+    create_file("foo.gemspec", <<-G)
+      Gem::Specification.new do |gem|
+        gem.name = "pry-byebug"
+        gem.version = "3.4.2"
+        gem.author = "David Rodríguez"
+        gem.summary = "Good stuff"
+      end
+    G
+
+    install_gemfile <<-G, :env => { "LANG" => "C" }
+      gemspec
+    G
+
+    expect(out).to include("Bundle complete!")
+  end
+
   context "when ruby version is specified in gemspec and gemfile" do
     it "installs when patch level is not specified and the version matches" do
       build_lib("foo", :path => bundled_app) do |s|