Relax polisher deps, gracefully fail if missing (rev 4)

Now polisher gem contains minimal runtime deps w/ mechanism
to catch runtime load errors. Components missing reqs will
not be accessible / calling methods on them will indicate
to install optional dependencies

Rebased against latest master

bin/git_gem_updater.rb

@@ -11,10 +11,7 @@
 # Copyright (C) 2013-2014 Red Hat, Inc.
 
 require 'colored'
-require 'curb'
-require 'json'
 require 'optparse'
-require 'nokogiri'
 
 require 'polisher/git'
 require 'polisher/gem'

lib/polisher/component.rb

@@ -0,0 +1,30 @@
+# Polisher Components & Component Helpers
+#
+# Licensed under the MIT license
+# Copyright (C) 2014 Red Hat, Inc.
+
+require 'active_support/core_ext'
+
+module Polisher
+  module Component
+    class Missing
+      def initialize(*args)
+        raise "polisher is missing a dependency - cannot instantiate"
+      end
+
+      def method_missing(method_id, *args, &bl)
+        raise "polisher is missing a dependency - cannot invoke #{method_id} on #{self}"
+      end
+    end # class MissingComponent
+
+    def self.verify(polisher_klass, *dependencies)
+      dependencies.each { |dep| require dep }
+    rescue LoadError
+      klass = polisher_klass.demodulize
+      polisher_module = "Polisher::#{polisher_klass.deconstantize}"
+      polisher_module.constantize.const_set(klass, Missing)
+    else
+      yield
+    end
+  end # module Component
+end # module Polisher

lib/polisher/errata.rb

@@ -3,73 +3,73 @@
 # Licensed under the MIT license
 # Copyright (C) 2013-2014 Red Hat, Inc.
 
-require 'json'
-require 'curb'
-
 require 'polisher/core'
+require 'polisher/component'
 
 module Polisher
-  class Errata
-    extend ConfHelpers
+  Component.verify("Errata", 'json', 'curb') do
+    class Errata
+      extend ConfHelpers
+
+      conf_attr :advisory_url, ''
+      conf_attr :package_prefix, 'rubygem-'
 
-    conf_attr :advisory_url, ''
-    conf_attr :package_prefix, 'rubygem-'
+      # Initialize/return singleton curl handle to query errata
+      def self.client
+        @curl ||= begin
+          curl = Curl::Easy.new
+          curl.ssl_verify_peer = false
+          curl.ssl_verify_host = false
+          curl.http_auth_types = :negotiate
+          curl.userpwd = ':'
+          curl
+        end
+      end
 
-    # Initialize/return singleton curl handle to query errata
-    def self.client
-      @curl ||= begin
-        curl = Curl::Easy.new
-        curl.ssl_verify_peer = false
-        curl.ssl_verify_host = false
-        curl.http_auth_types = :negotiate
-        curl.userpwd = ':'
-        curl
+      def self.clear!
+        @cached_url = nil
+        @cached_builds = nil
+        self
       end
-    end
 
-    def self.clear!
-      @cached_url = nil
-      @cached_builds = nil
-      self
-    end
+      def self.builds
+        @cached_url    ||= advisory_url
+        @cached_builds ||= nil
 
-    def self.builds
-      @cached_url    ||= advisory_url
-      @cached_builds ||= nil
+        if @cached_url != advisory_url || @cached_builds.nil?
+          client.url     = "#{advisory_url}/builds"
+          @cached_builds = client.get
+          @cached_builds = JSON.parse(client.body_str)
+        end
 
-      if @cached_url != advisory_url || @cached_builds.nil?
-        client.url     = "#{advisory_url}/builds"
-        @cached_builds = client.get
-        @cached_builds = JSON.parse(client.body_str)
+        @cached_builds
       end
 
-      @cached_builds
-    end
-
-    def self.versions_for(name, &bl)
-      versions = builds.collect do |tag, builds|
-        ErrataBuild.builds_matching(builds, name)
-      end.flatten
-      bl.call(:errata, name, versions) unless(bl.nil?) 
-      versions
-    end
-  end
+      def self.versions_for(name, &bl)
+        versions = builds.collect do |tag, builds|
+          ErrataBuild.builds_matching(builds, name)
+        end.flatten
+        bl.call(:errata, name, versions) unless(bl.nil?)
+        versions
+      end
+    end # class Errata
 
-  class ErrataBuild
-    def self.builds_matching(builds, name)
-      builds.collect { |build|
-        self.build_matches?(build, name) ? self.build_version(build, name) : nil
-      }.compact
-    end
+    class ErrataBuild
+      def self.builds_matching(builds, name)
+        builds.collect { |build|
+          self.build_matches?(build, name) ? self.build_version(build, name) : nil
+        }.compact
+      end
 
-    def self.build_matches?(build, name)
-      pkg,meta = *build.flatten
-      pkg =~ /^#{Errata.package_prefix}#{name}-([^-]*)-.*$/
-    end
+      def self.build_matches?(build, name)
+        pkg,meta = *build.flatten
+        pkg =~ /^#{Errata.package_prefix}#{name}-([^-]*)-.*$/
+      end
 
-    def self.build_version(build, name)
-      pkg,meta = *build.flatten
-      pkg.gsub(Errata.package_prefix, '').split('-')[1]
-    end
-  end
-end
+      def self.build_version(build, name)
+        pkg,meta = *build.flatten
+        pkg.gsub(Errata.package_prefix, '').split('-')[1]
+      end
+    end # class ErrataBuild
+  end # Component.verify(Errata)
+end # module Polisher

lib/polisher/fedora.rb

@@ -3,44 +3,44 @@
 # Licensed under the MIT license
 # Copyright (C) 2013-2014 Red Hat, Inc.
 
-require 'curb'
-require 'pkgwat'
-
 require 'polisher/bodhi'
+require 'polisher/component'
 
 module Polisher
-  class Fedora
-    PACKAGE_LIST = 'https://admin.fedoraproject.org/pkgdb/users/packages/'
+  Component.verify("Fedora", "curb", "pkgwat", "nokogiri") do
+    class Fedora
+      PACKAGE_LIST = 'https://admin.fedoraproject.org/pkgdb/users/packages/'
 
-    def self.client
-      @client ||= Curl::Easy.new
-    end
+      def self.client
+        @client ||= Curl::Easy.new
+      end
 
-    # Retrieve list of gems owned by the specified user
-    #
-    # @param [String] user Fedora username to lookup
-    # @return [Array<String>] list of gems which the user owns/has access to
-    def self.gems_owned_by(user)
-      client.url = "#{PACKAGE_LIST}#{user}"
-      client.http_get
-      packages = client.body_str
-      # TODO instantiate Polisher::Gem instances & return
-      Nokogiri::HTML(packages).xpath("//a[@class='PackageName']").
-                               select { |i| i.text =~ /rubygem-.*/ }.
-                               collect { |i| i.text.gsub(/rubygem-/, '') }
-    end
+      # Retrieve list of gems owned by the specified user
+      #
+      # @param [String] user Fedora username to lookup
+      # @return [Array<String>] list of gems which the user owns/has access to
+      def self.gems_owned_by(user)
+        client.url = "#{PACKAGE_LIST}#{user}"
+        client.http_get
+        packages = client.body_str
+        # TODO instantiate Polisher::Gem instances & return
+        Nokogiri::HTML(packages).xpath("//a[@class='PackageName']").
+                                 select { |i| i.text =~ /rubygem-.*/ }.
+                                 collect { |i| i.text.gsub(/rubygem-/, '') }
+      end
 
-    # Retrieve list of the versions of the specified package in the various
-    # Fedora releases.
-    #
-    # @param [String] name name of the package to lookup
-    # @param [Callable] bl optional callback to invoke with versions retrieved
-    # @return [Array<String>] list of versions in Fedora
-    def self.versions_for(name, &bl)
-      # simply dispatch to bodhi to get latest updates
-      Polisher::Bodhi.versions_for name do |target,name,versions|
-        bl.call(:fedora, name, versions) unless(bl.nil?) 
+      # Retrieve list of the versions of the specified package in the various
+      # Fedora releases.
+      #
+      # @param [String] name name of the package to lookup
+      # @param [Callable] bl optional callback to invoke with versions retrieved
+      # @return [Array<String>] list of versions in Fedora
+      def self.versions_for(name, &bl)
+        # simply dispatch to bodhi to get latest updates
+        Polisher::Bodhi.versions_for name do |target,name,versions|
+          bl.call(:fedora, name, versions) unless(bl.nil?)
+        end
       end
-    end
-  end # class Fedora
+    end # class Fedora
+  end # Component.verify("Fedora")
 end # module Polisher