[AggregateXCConfig] Properly merge the user_target_xcconfigs of multiple subspecs.

Closes https://github.com/CocoaPods/CocoaPods/issues/3813.

CHANGELOG.md

@@ -14,6 +14,13 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [#3830](https://github.com/CocoaPods/CocoaPods/pull/3830)
   [Eloy Durán](https://github.com/alloy)
 
+##### Bug Fixes
+
+* Properly merge the `user_target_xcconfig`s of multiple subspecs.  
+  [#3813](https://github.com/CocoaPods/CocoaPods/issues/3813)
+  [Samuel Giddins](https://github.com/segiddins)
+
+
 ## 0.38.0.beta.2
 
 ##### Enhancements

lib/cocoapods/generator/xcconfig/aggregate_xcconfig.rb

@@ -194,15 +194,16 @@ module Pod
           target.pod_targets_for_build_configuration(@configuration_name)
         end
 
-        # Returns the +user_target_xcconfig+ for all pod targets grouped by keys
+        # Returns the +user_target_xcconfig+ for all pod targets and their spec
+        # consumers grouped by keys
         #
         # @return [Hash{String,Hash{Target,String}]
         #
-        def user_target_xcconfig_values_by_target_by_key
+        def user_target_xcconfig_values_by_consumer_by_key
           pod_targets.each_with_object({}) do |target, hash|
             target.spec_consumers.each do |spec_consumer|
               spec_consumer.user_target_xcconfig.each do |k, v|
-                (hash[k] ||= {})[target] = v
+                (hash[k] ||= {})[spec_consumer] = v
               end
             end
           end
@@ -214,7 +215,7 @@ module Pod
         # @return [Hash{String, String}]
         #
         def merged_user_target_xcconfigs
-          settings = user_target_xcconfig_values_by_target_by_key
+          settings = user_target_xcconfig_values_by_consumer_by_key
           settings.each_with_object({}) do |(key, values_by_target), xcconfig|
             uniq_values = values_by_target.values.uniq
             values_are_bools = uniq_values.all? { |v| v =~ /(yes|no)/i }
@@ -222,7 +223,7 @@ module Pod
               # Boolean build settings
               if uniq_values.count > 1
                 UI.warn 'Can\'t merge user_target_xcconfig for pod targets: ' \
-                  "#{values_by_target.keys.map(&:label)}. Boolean build "\
+                  "#{values_by_target.keys.map(&:name)}. Boolean build "\
                   "setting #{key} has different values."
               else
                 xcconfig[key] = uniq_values.first
@@ -234,7 +235,7 @@ module Pod
               # Singular build settings
               if uniq_values.count > 1
                 UI.warn 'Can\'t merge user_target_xcconfig for pod targets: ' \
-                  "#{values_by_target.keys.map(&:label)}. Singular build "\
+                  "#{values_by_target.keys.map(&:name)}. Singular build "\
                   "setting #{key} has different values."
               else
                 xcconfig[key] = uniq_values.first

spec/unit/generator/xcconfig/aggregate_xcconfig_spec.rb

@@ -255,6 +255,14 @@ module Pod
               @xcconfig = @generator.generate
               @xcconfig.to_hash['OTHER_CPLUSPLUSFLAGS'].should == '-std=c++1y -stdlib=libc++'
             end
+
+            it 'adds values from all subspecs' do
+              @consumer_b.stubs(:user_target_xcconfig).returns('OTHER_CPLUSPLUSFLAGS' => '-std=c++1y')
+              consumer_c = mock(:user_target_xcconfig => { 'OTHER_CPLUSPLUSFLAGS' => '-stdlib=libc++' })
+              @pod_target_b.stubs(:spec_consumers).returns([@consumer_b, consumer_c])
+              @xcconfig = @generator.generate
+              @xcconfig.to_hash['OTHER_CPLUSPLUSFLAGS'].should == '-std=c++1y -stdlib=libc++'
+            end
           end
 
           describe 'with singular build settings' do