Auto merge of #4815 - asutoshpalai:plugin-hooks, r=segiddins

[Plugin] Life-cycle hooks

Implements life-cycle hook plugins.

This shows only [`before-install-all` hook](https://github.com/bundler/bundler/pull/4815/files#diff-0964e829e3db904ba7935ca3a933f111R22), but other hooks can be easily added in the similar fashion.

lib/bundler/installer.rb

@@ -20,6 +20,7 @@ class << self
     # For more information see the #run method on this class.
     def self.install(root, definition, options = {})
       installer = new(root, definition)
+      Plugin.hook("before-install-all", definition.dependencies)
       installer.run(options)
       installer
     end

lib/bundler/plugin.rb

@@ -16,8 +16,16 @@ class UnknownSourceError < PluginError; end
 
   module_function
 
-    @commands = {}
-    @sources = {}
+    def reset!
+      instance_variables.each {|i| remove_instance_variable(i) }
+
+      @sources = {}
+      @commands = {}
+      @hooks_by_event = Hash.new {|h, k| h[k] = [] }
+      @loaded_plugin_names = []
+    end
+
+    reset!
 
     # Installs a new plugin by the given name
     #
@@ -30,7 +38,7 @@ def install(names, options)
       save_plugins names, specs
     rescue PluginError => e
       specs.values.map {|spec| Bundler.rm_rf(spec.full_gem_path) } if specs
-      Bundler.ui.error "Failed to install plugin #{name}: #{e.message}\n  #{e.backtrace[0]}"
+      Bundler.ui.error "Failed to install plugin #{name}: #{e.message}\n  #{e.backtrace.join("\n ")}"
     end
 
     # Evaluates the Gemfile with a limited DSL and installs the plugins
@@ -137,21 +145,36 @@ def source_from_lock(locked_opts)
       src.new(locked_opts.merge("uri" => locked_opts["remote"]))
     end
 
+    # To be called via the API to register a hooks and corresponding block that
+    # will be called to handle the hook
+    def add_hook(event, &block)
+      @hooks_by_event[event.to_s] << block
+    end
+
+    # Runs all the hooks that are registered for the passed event
+    #
+    # It passes the passed arguments and block to the block registered with
+    # the api.
+    #
+    # @param [String] event
+    def hook(event, *args, &arg_blk)
+      return unless Bundler.settings[:plugins]
+
+      plugins = index.hook_plugins(event)
+      return unless plugins.any?
+
+      (plugins - @loaded_plugin_names).each {|name| load_plugin(name) }
+
+      @hooks_by_event[event].each {|blk| blk.call(*args, &arg_blk) }
+    end
+
     # currently only intended for specs
     #
     # @return [String, nil] installed path
     def installed?(plugin)
       Index.new.installed?(plugin)
     end
 
-    # Used by specs
-    def reset!
-      instance_variables.each {|i| remove_instance_variable(i) }
-
-      @sources = {}
-      @commands = {}
-    end
-
     # Post installation processing and registering with index
     #
     # @param [Array<String>] plugins list to be installed
@@ -162,7 +185,7 @@ def save_plugins(plugins, specs, optional_plugins = [])
       plugins.each do |name|
         spec = specs[name]
         validate_plugin! Pathname.new(spec.full_gem_path)
-        installed = register_plugin name, spec, optional_plugins.include?(name)
+        installed = register_plugin(name, spec, optional_plugins.include?(name))
         Bundler.ui.info "Installed plugin #{name}" if installed
       end
     end
@@ -190,9 +213,11 @@ def validate_plugin!(plugin_path)
     def register_plugin(name, spec, optional_plugin = false)
       commands = @commands
       sources = @sources
+      hooks = @hooks_by_event
 
       @commands = {}
       @sources = {}
+      @hooks_by_event = Hash.new {|h, k| h[k] = [] }
 
       load_paths = spec.load_paths
       add_to_load_path(load_paths)
@@ -208,12 +233,14 @@ def register_plugin(name, spec, optional_plugin = false)
         Bundler.rm_rf(path)
         false
       else
-        index.register_plugin name, path.to_s, load_paths, @commands.keys, @sources.keys
+        index.register_plugin(name, path.to_s, load_paths, @commands.keys,
+          @sources.keys, @hooks_by_event.keys)
         true
       end
     ensure
       @commands = commands
       @sources = sources
+      @hooks_by_event = hooks
     end
 
     # Executes the plugins.rb file
@@ -228,6 +255,8 @@ def load_plugin(name)
       add_to_load_path(index.load_paths(name))
 
       load path.join(PLUGIN_FILE_NAME)
+
+      @loaded_plugin_names << name
     rescue => e
       Bundler.ui.error "Failed loading plugin #{name}: #{e.message}"
       raise

lib/bundler/plugin/api.rb

@@ -44,6 +44,10 @@ def self.source(source, cls = self)
         Plugin.add_source source, cls
       end
 
+      def self.hook(event, &block)
+        Plugin.add_hook(event, &block)
+      end
+
       # The cache dir to be used by the plugins for storage
       #
       # @return [Pathname] path of the cache dir

lib/bundler/plugin/index.rb

@@ -24,6 +24,7 @@ def initialize
         @plugin_paths = {}
         @commands = {}
         @sources = {}
+        @hooks = {}
         @load_paths = {}
 
         load_index(global_index_file, true)
@@ -39,7 +40,7 @@ def initialize
       # @param [Array<String>] load_paths for the plugin
       # @param [Array<String>] commands that are handled by the plugin
       # @param [Array<String>] sources that are handled by the plugin
-      def register_plugin(name, path, load_paths, commands, sources)
+      def register_plugin(name, path, load_paths, commands, sources, hooks)
         old_commands = @commands.dup
 
         common = commands & @commands.keys
@@ -50,6 +51,8 @@ def register_plugin(name, path, load_paths, commands, sources)
         raise SourceConflict.new(name, common) unless common.empty?
         sources.each {|k| @sources[k] = name }
 
+        hooks.each {|e| (@hooks[e] ||= []) << name }
+
         @plugin_paths[name] = path
         @load_paths[name] = load_paths
         save_index
@@ -98,6 +101,11 @@ def source_plugin(name)
         @sources[name]
       end
 
+      # Returns the list of plugin names handling the passed event
+      def hook_plugins(event)
+        @hooks[event] || []
+      end
+
     private
 
       # Reads the index file from the directory and initializes the instance
@@ -112,12 +120,14 @@ def load_index(index_file, global = false)
           break unless valid_file
 
           data = index_f.read
+
           require "bundler/yaml_serializer"
           index = YAMLSerializer.load(data)
 
-          @plugin_paths.merge!(index["plugin_paths"])
-          @load_paths.merge!(index["load_paths"])
           @commands.merge!(index["commands"])
+          @hooks.merge!(index["hooks"])
+          @load_paths.merge!(index["load_paths"])
+          @plugin_paths.merge!(index["plugin_paths"])
           @sources.merge!(index["sources"]) unless global
         end
       end
@@ -127,10 +137,11 @@ def load_index(index_file, global = false)
       # to be only String key value pairs)
       def save_index
         index = {
+          "commands"     => @commands,
+          "hooks"        => @hooks,
+          "load_paths"   => @load_paths,
           "plugin_paths" => @plugin_paths,
-          "load_paths" => @load_paths,
-          "commands" => @commands,
-          "sources" => @sources,
+          "sources"      => @sources,
         }
 
         require "bundler/yaml_serializer"

spec/bundler/plugin/api_spec.rb

@@ -38,6 +38,17 @@
         UserPluginClass.source "a_source", NewClass
       end
     end
+
+    describe "#hook" do
+      it "accepts a block and passes it to Plugin module" do
+        foo = double("tester")
+        expect(foo).to receive(:called)
+
+        expect(Bundler::Plugin).to receive(:add_hook).with("post-foo").and_yield
+
+        Bundler::Plugin::API.hook("post-foo") { foo.called }
+      end
+    end
   end
 
   context "bundler interfaces provided" do