[Validator] Explain why linting failed

lib/cocoapods/command/lib.rb

@@ -160,7 +160,7 @@ module Pod
             else
               spec_name = podspec
               spec_name = validator.spec.name if validator.spec
-              message = "#{spec_name} did not pass validation."
+              message = "#{spec_name} did not pass validation, due to #{validator.failure_reason}."
 
               if @clean
                 message << "\nYou can use the `--no-clean` option to inspect " \

lib/cocoapods/command/spec/lint.rb

@@ -42,7 +42,7 @@ module Pod
 
         def run
           UI.puts
-          invalid_count = 0
+          failure_reasons = []
           podspecs_to_lint.each do |podspec|
             validator                = Validator.new(podspec, @source_urls)
             validator.quick          = @quick
@@ -53,7 +53,7 @@ module Pod
             validator.only_subspec   = @only_subspec
             validator.use_frameworks = @use_frameworks
             validator.validate
-            invalid_count += 1 unless validator.validated?
+            failure_reasons << validator.failure_reason
 
             unless @clean
               UI.puts "Pods project available at `#{validator.validation_dir}/Pods/Pods.xcodeproj` for inspection."
@@ -63,11 +63,17 @@ module Pod
 
           count = podspecs_to_lint.count
           UI.puts "Analyzed #{count} #{'podspec'.pluralize(count)}.\n\n"
-          if invalid_count == 0
+
+          failure_reasons.compact!
+          if failure_reasons.empty?
             lint_passed_message = count == 1 ? "#{podspecs_to_lint.first.basename} passed validation." : 'All the specs passed validation.'
             UI.puts lint_passed_message.green << "\n\n"
           else
-            raise Informative, count == 1 ? 'The spec did not pass validation.' : "#{invalid_count} out of #{count} specs failed validation."
+            raise Informative, if count == 1
+                                 "The spec did not pass validation, due to #{failure_reasons.first}."
+                               else
+                                 "#{invalid_count} out of #{count} specs failed validation."
+                               end
           end
           podspecs_tmp_dir.rmtree if podspecs_tmp_dir.exist?
         end

lib/cocoapods/validator.rb

+require 'active_support/core_ext/array'
+require 'active_support/core_ext/string/inflections'
+
 module Pod
   # Validates a Specification.
   #
@@ -111,6 +114,23 @@ module Pod
       UI.puts
     end
 
+    def failure_reason
+      results_by_type = results.group_by(&:type)
+      results_by_type.default = []
+      return nil if validated?
+      reasons = []
+      if (size = results_by_type[:error].size) && size > 0
+        reasons << "#{size} #{'error'.pluralize(size)}"
+      end
+      if !allow_warnings && (size = results_by_type[:warning].size) && size > 0
+        reason = "#{size} #{'warning'.pluralize(size)}"
+        pronoun = size == 1 ? 'it' : 'them'
+        reason <<  " (but you can use `--allow-warnings` to ignore #{pronoun})" if reasons.empty?
+        reasons << reason
+      end
+      reasons.to_sentence
+    end
+
     #-------------------------------------------------------------------------#
 
     #  @!group Configuration

spec/functional/command/spec_spec.rb

@@ -197,8 +197,10 @@ module Pod
 
       it 'lints a given podspec' do
         cmd = command('spec', 'lint', '--quick', @spec_path)
-        lambda { cmd.run }.should.raise Informative
+        exception = lambda { cmd.run }.should.raise Informative
         UI.output.should.include 'Missing license type'
+        exception.message.should.match /due to 1 warning /
+        exception.message.should.match /use `--allow-warnings` to ignore it\)/
       end
 
       it 'respects the --allow-warnings option' do