[migration] Add customizable slugs.

* Implement CustomizableSlug mixin to wrap and improve FriendlyId.
* Add slug fields to models and views.
* Redirect show requests to old slugs based on history.
* Describe behavior in specs.

app/controllers/application_controller.rb

@@ -107,4 +107,13 @@ def page_title(value=nil)
     end
   end
   helper_method :page_title
+
+  # Preserve old links to resources by redirecting to their current location.
+  #
+  # The "friendly_id" slug history tracks the resource's slug over time. If a resource is available under a newer slug name, redirect its "show" action to the current name. E.g. "/request/old-name" will redirect to "/request/new-name" if the slug was changed from "old-name" to "new-name".
+  def redirect_historical_slugs
+    if self.action_name == "show" && request.path != resource_path(resource)
+      return redirect_to resource, :status => :moved_permanently
+    end
+  end
 end

app/controllers/companies_controller.rb

@@ -4,6 +4,7 @@ class CompaniesController < InheritedResources::Base
                   :resource => [:join, :leave]
 
   before_filter :authenticate_user!, :except => [:index, :show, :tag]
+  before_filter :redirect_historical_slugs
 
   def tag
     @tag = params[:tag]

app/controllers/groups_controller.rb

@@ -4,6 +4,7 @@ class GroupsController < InheritedResources::Base
                   :resource => [:join, :leave]
 
   before_filter :authenticate_user!, :except => [:index, :show, :tag]
+  before_filter :redirect_historical_slugs
 
   def tag
     @tag = params[:tag]

app/controllers/people_controller.rb

@@ -8,6 +8,7 @@ class PeopleController < InheritedResources::Base
   before_filter :require_owner_or_admin!, :only => [:edit, :update, :destroy]
   before_filter :pick_photo_input, :only => [:update, :create]
   before_filter :set_user_id_if_admin, :only => [:update, :create]
+  before_filter :redirect_historical_slugs
 
   def index
     @view = :grid if params[:grid]

app/controllers/projects_controller.rb

@@ -4,6 +4,7 @@ class ProjectsController < InheritedResources::Base
                   :resource => [:join, :leave]
 
   before_filter :authenticate_user!, :except => [:index, :show, :tag]
+  before_filter :redirect_historical_slugs
 
   def tag
     @tag = params[:tag]

app/controllers/users_controller.rb

@@ -35,6 +35,8 @@ def welcome
         @possible_duplicates += Person.unclaimed.where(name_part_query, *name_parts.map{|p| "%#{p}%"}).take(10)
 
         @possible_duplicates.uniq!
+
+        @person.send(:set_slug)
       end
     end
   end

app/mixins/customizable_slug.rb

@@ -0,0 +1,113 @@
+# = CustomizableSlug
+#
+# This mixin provides a easy-to-use wrapper for setting up customizable slugs
+# using the <tt>friendly_id</tt> plugin.
+#
+# @example To add a customizable slug whose default value is based on the :name
+# field, add this to your ActiveRecord model:
+#
+#   class MyModel
+#     customizable_slug_from :name
+#   end
+#
+# @example To use the customizable field:
+#
+#   m = MyModel.new(:name => "foo")
+#
+#   m.save
+#   m.slug # => "foo"
+#
+#   m.custom_slug = "bar"
+#   m.save
+#   m.slug # => "bar"
+module CustomizableSlug
+
+  # Override behavior of gem.
+  require 'friendly_id/slug_generator'
+  class CustomizableSlugGenerator < FriendlyId::SlugGenerator
+    # When generating the slug, if there's a conflict, stop immediately and
+    # mark the record as an error so user can pick something else.
+    #
+    # The gem's original behavior is to always generate a unique slug, even if
+    # this means adding a number to the end of it. This is bad design because
+    # if the user wants to be "foo", but that's taken, they'll end up as
+    # "foo-2", rather than being told to pick another slug.
+    def generate
+      if conflict?
+        sluggable.errors.add(:custom_slug, I18n.t('activerecord.errors.messages.taken'))
+      end
+      return normalized
+    end
+
+    # Check history for conflicts, if using history.
+    #
+    # The gem's original behavior doesn't check history, so if you try to
+    # create a conflicting record, the #save will fail with a raw SQL
+    # uniqueness constraint error.
+    def conflicts
+      # If any regular conflicts are found, return them immediately.
+      scope = super
+      return scope if scope.count > 0
+
+      # If no regular conflicts are found, search the history.
+      if friendly_id_config.model_class.included_modules.include?(FriendlyId::History)
+        history = FriendlyId::Slug.where(:slug => normalized, :sluggable_type => self.sluggable.class.to_s)
+        unless self.sluggable.new_record?
+          # If record exists, exclude it from the history check.
+          history = history.where('sluggable_id <> ?', self.sluggable.id)
+        end
+
+        return history if history.count > 0
+      end
+
+      # No conflicts of any sort found.
+      return []
+    end
+  end
+
+  def self.included(base)
+    base.send(:extend, ::CustomizableSlug::ClassMethods)
+  end
+
+  module ClassMethods
+    # Managing customizable custom slug for +attribute+, e.g. :name.
+    def customizable_slug_from(attribute)
+      # Attribute which contains the source value to use for generating the
+      # slug, e.g. :name.
+      cattr_accessor :friendly_id_source_attribute
+      self.friendly_id_source_attribute = attribute
+
+      # Activate "friendly_id" plugin.
+      extend FriendlyId
+      friendly_id :custom_slug_or_source, :use => :history, :slug_generator_class => ::CustomizableSlug::CustomizableSlugGenerator
+
+      # Add validation for "custom_slug" field.
+      validate :validate_custom_slug
+    end
+  end
+
+  # Return the user-specified custom slug or the friendly id for this record.
+  def custom_slug
+    @custom_slug.presence || self.friendly_id
+  end
+
+  # Set the custom slug to +value+.
+  def custom_slug=(value)
+    @custom_slug = value
+  end
+
+  # Return the custom slug or the value of the attribute that contains the source value.
+  def custom_slug_or_source
+    @custom_slug.presence || "#{self.send(self.class.friendly_id_source_attribute)}"
+  end
+
+  def validate_custom_slug
+    # Ensure the slug starts with a letter, or Rails will run #to_i on it to
+    # get a number and find the record by numeric id rather than the slug. :(
+    #
+    # TODO Figure out what to do about slugs that really start with a digit, e.g. "37signals".
+    if @custom_slug.present? && @custom_slug !~ /^\D/
+      self.errors.add(:custom_slug, I18n.t('activerecord.errors.must_start_with_non_digit'))
+    end
+  end
+end

app/models/company.rb

@@ -14,6 +14,8 @@ class Company < ActiveRecord::Base
 
   import_image_from_url_as :logo
 
+  customizable_slug_from :name
+
   has_many :company_projects
   has_many :projects, :through => :company_projects
 

app/models/group.rb

@@ -14,6 +14,8 @@ class Group < ActiveRecord::Base
 
   import_image_from_url_as :logo
 
+  customizable_slug_from :name
+
   has_many :group_projects
   has_many :projects, :through => :group_projects
 

app/models/person.rb

@@ -17,6 +17,8 @@ class Person < ActiveRecord::Base
 
   import_image_from_url_as :photo, :gravatar => true
 
+  customizable_slug_from :name
+
   belongs_to :user
   accepts_nested_attributes_for :user, :update_only => true
 
@@ -77,6 +79,7 @@ def self.find_or_create_sample(create_backreference=true)
     end
     return person
   end
+
 end
 
 

app/models/project.rb

@@ -14,6 +14,8 @@ class Project < ActiveRecord::Base
 
   import_image_from_url_as :logo
 
+  customizable_slug_from :name
+
   has_many :project_memberships
   has_many :people, :through => :project_memberships
 

app/views/companies/_form.html.haml

@@ -2,6 +2,7 @@
   = display_errors_for @company
   = f.inputs do
     = f.input :name
+    = render 'site/custom_slug_field', :form => f
     = f.input :url
     = f.input :address, :as => :string
     = f.input :description

app/views/groups/_form.html.haml

@@ -2,6 +2,7 @@
   = display_errors_for @group
   = f.inputs do
     = f.input :name
+    = render 'site/custom_slug_field', :form => f
     = f.input :url
     = f.input :mailing_list
     = f.input :description

app/views/people/_form.html.haml

@@ -3,7 +3,7 @@
   = display_errors_for @person
   = f.inputs do
     = f.input :name
-    -# = f.input :twitter
+    = render 'site/custom_slug_field', :form => f
     - unless @person.new_record?
       = f.semantic_fields_for :user do |u|
         = u.input :email

app/views/projects/_form.html.haml

@@ -2,6 +2,7 @@
   = display_errors_for @project
   = f.inputs do
     = f.input :name
+    = render 'site/custom_slug_field', :form => f
     = f.input :url
     = f.input :description
     = f.input :tag_list, :as => :text, :input_html => {:class => 'tags'}

app/views/site/_custom_slug_field.html.haml

@@ -0,0 +1,10 @@
+-# Display the form field for a custom slug.
+-#
+-# ARGUMENTS:
+-# * form: The Rails form instance.
+- hint = "%{example} %{url}/<em><b>%{my}-%{model}</b></em>" % { |
+  :example => t('field.example.fragment'),                      |
+  :url => "#{SETTINGS.organization.url}/#{controller_path}",    |
+  :my => t('field.my.fragment'),                                |
+  :model => t("activerecord.models.#{form.send(:model_name).underscore}").underscore }
+= form.input :custom_slug, :hint => hint.html_safe

config/initializers/customizable_slug.rb

@@ -0,0 +1,3 @@
+class ActiveRecord::Base
+  include CustomizableSlug
+end

config/locales/en.yml

@@ -7,6 +7,7 @@ en:
     address: "Address"
     category: "Category"
     created_at: "Created at"
+    custom_slug: "URL slug"
     description: "Description"
     email: "Email address"
     location: "Location"
@@ -30,6 +31,8 @@ en:
       person:
         bio: "Bio"
         location: "Location"
+    errors:
+      must_start_with_non_digit: "must start with a non-digit"
 
   sign_in: Sign In
   group:
@@ -178,6 +181,8 @@ en:
       label: "Date added" # people#index
     email_address:
       label: "Email address" # authentications#_login
+    example:
+      fragment: "e.g." # site#_custom_slug_field
     group_list:
       title: "Groups" # people#show
     import_file:
@@ -191,6 +196,8 @@ en:
       title: "Meeting Info" # groups#show
     members:
       title: "Members" # group#show
+    my:
+      fragment: "my" # site#_custom_slug_field
     name:
       label: "Name" # people#index
     project_list:

config/locales/fr.yml

@@ -5,6 +5,7 @@ fr:
     address: "Adresse"
     category: "Catégorie"
     created_at: "Créé le"
+    custom_slug: "Sobriquet de l'URL" # TODO review translation
     description: "Description"
     email: "Adresse email ou identifiant"
     location: "Adresse"
@@ -40,6 +41,8 @@ fr:
       person:
         bio: "Bio"
         location: "Localisation"
+    errors:
+      must_start_with_non_digit: "doit commencer par un non-chiffres" # TODO review translation
 
   sign_in: Connexion
   group:
@@ -185,6 +188,8 @@ fr:
       label: "Date de création" # people#index
     email_address:
       label: "Adresse email ou identifiant" # authentications#_login
+    example:
+      fragment: "pour exemple" # site#_custom_slug_field # TODO review translation
     group_list:
       title: "Groupes" # people#show
     import_file:
@@ -198,6 +203,8 @@ fr:
       title: "Infos réunion" # groups#show
     members:
       title: "Membres" # groups#show
+    my:
+      fragment: "mon" # site#_custom_slug_field # TODO review translation
     name:
       label: "Nom" # people#index
     project_list:

db/migrate/20110924171944_create_friendly_id_slugs.rb

@@ -0,0 +1,18 @@
+class CreateFriendlyIdSlugs < ActiveRecord::Migration
+
+  def self.up
+    create_table :friendly_id_slugs do |t|
+      t.string   :slug,           :null => false
+      t.integer  :sluggable_id,   :null => false
+      t.string   :sluggable_type, :limit => 40
+      t.datetime :created_at
+    end
+    add_index :friendly_id_slugs, :sluggable_id
+    add_index :friendly_id_slugs, [:slug, :sluggable_type], :unique => true
+    add_index :friendly_id_slugs, :sluggable_type
+  end
+
+  def self.down
+    drop_table :friendly_id_slugs
+  end
+end

db/migrate/20110924171945_add_slugs.rb

@@ -0,0 +1,20 @@
+class AddSlugs < ActiveRecord::Migration
+  TABLES = %w[people companies projects groups]
+
+  def self.up
+    for table in TABLES
+      add_column table, :slug, :string
+      add_index table,  :slug, :unique => true
+
+      # Add slug to all records
+      table.classify.constantize.find_each(&:save)
+    end
+  end
+
+  def self.down
+    for table in TABLES
+      remove_index table,  :slug
+      remove_column table, :slug
+    end
+  end
+end