[ModuleMap] Explicitly declare private headers

lib/cocoapods/generator/module_map.rb

@@ -10,10 +10,15 @@ module Pod
       #
       attr_reader :target
 
+      # @return [Array] the private headers of the module
+      #
+      attr_accessor :private_headers
+
       # @param  [Target] target @see target
       #
       def initialize(target)
         @target = target
+        @private_headers = []
       end
 
       # Generates and saves the Info.plist to the given path.
@@ -35,14 +40,24 @@ module Pod
       # @return [String]
       #
       def generate
-        <<-eos.strip_heredoc
+        result = <<-eos.strip_heredoc
           framework module #{target.product_module_name} {
             umbrella header "#{target.umbrella_header_path.basename}"
 
             export *
             module * { export * }
-          }
         eos
+
+        result << "\n#{generate_private_header_exports}" unless private_headers.empty?
+        result << "}\n"
+      end
+
+      private
+
+      def generate_private_header_exports
+        private_headers.reduce('') do |string, header|
+          string << %(  private header "#{header}\n")
+        end
       end
     end
   end

lib/cocoapods/installer/target_installer.rb

@@ -107,12 +107,16 @@ module Pod
       # Creates the module map file which ensures that the umbrella header is
       # recognized with a customized path
       #
+      # @yield_param [Generator::ModuleMap]
+      #              yielded once to configure the private headers
+      #
       # @return [void]
       #
       def create_module_map
         path = target.module_map_path
         UI.message "- Generating module map file at #{UI.path(path)}" do
           generator = Generator::ModuleMap.new(target)
+          yield generator if block_given?
           generator.save_as(path)
           add_file_to_support_group(path)
 

lib/cocoapods/installer/target_installer/pod_target_installer.rb

@@ -22,7 +22,9 @@ module Pod
           create_xcconfig_file
           if target.requires_frameworks?
             create_info_plist_file
-            create_module_map
+            create_module_map do |generator|
+              generator.private_headers += target.file_accessors.flat_map(&:private_headers).map(&:basename)
+            end
             create_umbrella_header do |generator|
               generator.imports += target.file_accessors.flat_map(&:public_headers).map(&:basename)
             end