validate gemspec specifications (with a test)

closes rubygems#3639

lib/bundler/dsl.rb

@@ -48,9 +48,10 @@ def gemspec(opts = nil)
 
       case gemspecs.size
       when 1
-        spec = Bundler.load_gemspec(gemspecs.first)
-        raise InvalidOption, "There was an error loading the gemspec at #{gemspecs.first}." unless spec
+        spec = load_valid_gemspec(gemspecs.first)
+
         gem spec.name, :path => path, :glob => glob
+
         group(development_group) do
           spec.development_dependencies.each do |dep|
             gem dep.name, *(dep.requirement.as_list + [:type => :development])
@@ -59,7 +60,8 @@ def gemspec(opts = nil)
       when 0
         raise InvalidOption, "There are no gemspecs at #{expanded_path}."
       else
-        raise InvalidOption, "There are multiple gemspecs at #{expanded_path}. Please use the :name option to specify which one."
+        raise InvalidOption, "There are multiple gemspecs at #{expanded_path}. " \
+          "Please use the :name option to specify which one should be used."
       end
     end
 
@@ -358,6 +360,21 @@ def check_primary_source_safety(source)
       end
     end
 
+    def load_valid_gemspec(path)
+      spec = Bundler.load_gemspec(path)
+
+      unless spec
+        raise InvalidOption, "There was an error loading the gemspec at " \
+          "#{path}. Make sure you can build the gem, then try again."
+      end
+
+      spec.validate
+      spec
+    rescue Gem::InvalidSpecificationException => e
+      raise InvalidOption, "The gemspec at #{path} is not valid. " \
+        "The validation error was '#{e.message}'"
+    end
+
     class DSLError < GemfileError
       # @return [String] the description that should be presented to the user.
       #

spec/bundler/dsl_spec.rb

@@ -187,4 +187,18 @@
         to raise_error(Bundler::GemfileError, /There was an error parsing `Gemfile`: can't modify frozen String. Bundler cannot continue./)
     end
   end
+
+  describe "#gemspec" do
+    it "errors on invalid specs" do
+      File.open(bundled_app("foo.gemspec"), "w") do |f|
+        f.write <<-G
+          Gem::Specification.new do |s|
+            s.name = "foo"
+          end
+        G
+      end
+      expect(Bundler).to receive(:default_gemfile).and_return(bundled_app("Gemfile"))
+      expect { subject.gemspec }.to raise_error(Bundler::InvalidOption).with_message(/missing value for attribute version/)
+    end
+  end
 end