[Installer] Added pre install hooks.

They are called after the pods have been downloaded but before the targets are
integrated in the Pods.xcodeproj.

closes #486

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ###### Enhancements
 
+- Added a pre install hook to the Podfile and to root specifications.
+  [#486](https://github.com/CocoaPods/CocoaPods/issues/486)
 - Support for `header_mappings_dir` attribute in subspecs.
 - Refactored UI.
 

lib/cocoapods/installer.rb

@@ -121,6 +121,9 @@ module Pod
       end
 
       ui_title("Generating support files", '', 2) do
+        ui_message "- Running pre install hooks" do
+          run_pre_install_hooks
+        end
 
         ui_message("- Installing targets", '', 2) do
           generate_target_support_files
@@ -144,6 +147,15 @@ module Pod
       end
     end
 
+    def run_pre_install_hooks
+      pods_by_target.each do |target_definition, pods|
+        pods.each do |pod|
+          pod.top_specification.pre_install(pod, target_definition)
+        end
+      end
+      @podfile.pre_install!(self)
+    end
+
     def run_post_install_hooks
       # we loop over target installers instead of pods, because we yield the target installer
       # to the spec post install hook.

lib/cocoapods/podfile.rb

@@ -472,6 +472,17 @@ module Pod
       @target_definition = parent
     end
 
+    # This hook allows you to make any changes to the downloaded Pods and to
+    # their targets before they are installed.
+    #
+    #   pre_install do |installer|
+    #     # Do something fancy!
+    #   end
+    #
+    def pre_install(&block)
+      @pre_install_callback = block
+    end
+
     # This hook allows you to make any last changes to the generated Xcode project
     # before it is written to disk, or any other tasks you might want to perform.
     #
@@ -532,6 +543,10 @@ module Pod
       configs_array.inject({}) { |hash, config| hash.merge(config) }
     end
 
+    def pre_install!(installer)
+      @pre_install_callback.call(installer) if @pre_install_callback
+    end
+
     def post_install!(installer)
       @post_install_callback.call(installer) if @post_install_callback
     end

lib/cocoapods/specification.rb

@@ -429,20 +429,36 @@ module Pod
       header_mappings_dir ? from.relative_path_from(header_mappings_dir) : from.basename
     end
 
+    # This is a convenience method which gets called after all pods have been
+    # downloaded but before they have been installed, and the Xcode project and
+    # related files have been generated. (It receives the Pod::LocalPod
+    # instance generated form the specification and the #
+    # Pod::Podfile::TargetDefinition instance for the current target.) Override
+    # this to, for instance, to run any build script:
+    #
+    #   Pod::Spec.new do |s|
+    #     def pre_install(pod, target_definition)
+    #       Dir.chdir(pod.root){ `sh make.sh` }
+    #     end
+    #   end
+    def pre_install(pod, target_definition)
+    end
+
     # This is a convenience method which gets called after all pods have been
     # downloaded, installed, and the Xcode project and related files have been
-    # generated. (It receives the Pod::Installer::Target instance for the current
-    # target.) Override this to, for instance, add to the prefix header:
+    # generated. (It receives the Pod::Installer::TargetInstaller instance for
+    # the current target.) Override this to, for instance, add to the prefix
+    # header:
     #
     #   Pod::Spec.new do |s|
-    #     def s.post_install(target)
-    #       prefix_header = config.project_pods_root + target.prefix_header_filename
+    #     def s.post_install(target_installer)
+    #       prefix_header = config.project_pods_root + target_installer.prefix_header_filename
     #       prefix_header.open('a') do |file|
     #         file.puts(%{#ifdef __OBJC__\n#import "SSToolkitDefines.h"\n#endif})
     #       end
     #     end
     #   end
-    def post_install(target)
+    def post_install(target_installer)
     end
 
     def podfile?

spec/integration_spec.rb

@@ -249,6 +249,22 @@ else
         FileUtils.cp_r(fixture('integration/.'), config.project_pods_root)
       end
 
+      it "runs the optional pre_install callback defined in the Podfile _before_ the targets are integrated but _after_ the pods have been downloaded" do
+        podfile = Pod::Podfile.new do
+          self.platform platform
+          xcodeproj 'dummy'
+          pod 'SSZipArchive', '0.1.0'
+
+          pre_install do |installer|
+            memo = "PODS:#{installer.pods * ', '} TARGETS:#{installer.project.targets.to_a * ', '}"
+            File.open(config.project_pods_root + 'memo.txt', 'w') {|f| f.puts memo}
+          end
+        end
+        resolver = Pod::Resolver.new(podfile, nil, Pod::Sandbox.new(config.project_pods_root))
+        SpecHelper::Installer.new(resolver).install!
+        File.open(config.project_pods_root + 'memo.txt','rb').read.should == "PODS:SSZipArchive (0.1.0) TARGETS:\n"
+      end
+
       it "runs the optional post_install callback defined in the Podfile _before_ the project is saved to disk" do
         podfile = Pod::Podfile.new do
           self.platform platform

spec/unit/podfile_spec.rb

@@ -79,6 +79,16 @@ describe "Pod::Podfile" do
     Pod::Podfile.new { set_arc_compatibility_flag! }.should.set_arc_compatibility_flag
   end
 
+  it "stores a block that will be called with the Installer before the target integration" do
+    yielded = nil
+    Pod::Podfile.new do
+      pre_install do |installer|
+        yielded = installer
+      end
+    end.pre_install!(:an_installer)
+    yielded.should == :an_installer
+  end
+
   it "stores a block that will be called with the Installer instance once installation is finished (but the project is not written to disk yet)" do
     yielded = nil
     Pod::Podfile.new do