Allow to set size limit for slug (#809)

lib/friendly_id/base.rb

@@ -178,6 +178,9 @@ module Base
     #   Configures the name of the column where FriendlyId will store the slug.
     #   Defaults to `:slug`.
     #
+    # @option options [Integer] :slug_limit Available when using `:slugged`.
+    #   Configures the limit of the slug. This option has no default value.
+    #
     # @option options [Symbol] :slug_generator_class Available when using `:slugged`.
     #   Sets the class used to generate unique slugs. You should not specify this
     #   unless you're doing some extensive hacking on FriendlyId. Defaults to

lib/friendly_id/initializer.rb

@@ -52,6 +52,10 @@
   #
   # config.slug_column = 'slug'
   #
+  # By default, slug has no size limit, but you can change it if you wish.
+  #
+  # config.slug_limit = 255
+  #
   # When FriendlyId can not generate a unique ID from your base method, it appends
   # a UUID, separated by a single dash. You can configure the character used as the
   # separator. If you're upgrading from FriendlyId 4, you may wish to replace this

lib/friendly_id/slugged.rb

@@ -288,7 +288,9 @@ def self.included(model_class)
     # @param [#to_s] value The value used as the basis of the slug.
     # @return The candidate slug text, without a sequence.
     def normalize_friendly_id(value)
-      value.to_s.parameterize
+      value = value.to_s.parameterize
+      value = value[0...friendly_id_config.slug_limit] if friendly_id_config.slug_limit
+      value
     end
 
     # Whether to generate a new slug.
@@ -299,10 +301,56 @@ def should_generate_new_friendly_id?
       send(friendly_id_config.slug_column).nil? && !send(friendly_id_config.base).nil?
     end
 
+    # Public: Resolve conflicts.
+    #
+    # This method adds UUID to first candidate and truncates (if `slug_limit` is set).
+    #
+    # Examples:
+    #
+    #   resolve_friendly_id_conflict(['12345'])
+    #   # => '12345-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
+    #
+    #   FriendlyId.defaults { |config| config.slug_limit = 40 }
+    #   resolve_friendly_id_conflict(['12345'])
+    #   # => '123-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
+    #
+    # candidates - the Array with candidates.
+    #
+    # Returns the String with new slug.
     def resolve_friendly_id_conflict(candidates)
-      [candidates.first, SecureRandom.uuid].compact.join(friendly_id_config.sequence_separator)
+      uuid = SecureRandom.uuid
+      [
+        apply_slug_limit(candidates.first, uuid),
+        uuid
+      ].compact.join(friendly_id_config.sequence_separator)
     end
 
+    # Private: Apply slug limit to candidate.
+    #
+    # candidate - the String with candidate.
+    # uuid      - the String with UUID.
+    #
+    # Return the String with truncated candidate.
+    def apply_slug_limit(candidate, uuid)
+      return candidate unless candidate && friendly_id_config.slug_limit
+
+      candidate[0...candidate_limit(uuid)]
+    end
+    private :apply_slug_limit
+
+    # Private: Get max length of candidate.
+    #
+    # uuid - the String with UUID.
+    #
+    # Returns the Integer with max length.
+    def candidate_limit(uuid)
+      [
+        friendly_id_config.slug_limit - uuid.size - friendly_id_config.sequence_separator.size,
+        0
+      ].max
+    end
+    private :candidate_limit
+
     # Sets the slug.
     def set_slug(normalized_slug = nil)
       if should_generate_new_friendly_id?
@@ -334,11 +382,11 @@ def unset_slug_if_invalid
     end
     private :unset_slug_if_invalid
 
-    # This module adds the `:slug_column`, and `:sequence_separator`, and
-    # `:slug_generator_class` configuration options to
+    # This module adds the `:slug_column`, and `:slug_limit`, and `:sequence_separator`,
+    # and `:slug_generator_class` configuration options to
     # {FriendlyId::Configuration FriendlyId::Configuration}.
     module Configuration
-      attr_writer :slug_column, :sequence_separator
+      attr_writer :slug_column, :slug_limit, :sequence_separator
       attr_accessor :slug_generator_class
 
       # Makes FriendlyId use the slug column for querying.
@@ -361,6 +409,11 @@ def sequence_separator
       def slug_column
         @slug_column ||= defaults[:slug_column]
       end
+
+      # The limit that will be used for slug.
+      def slug_limit
+        @slug_limit ||= defaults[:slug_limit]
+      end
     end
   end
 end

test/slugged_test.rb

@@ -271,6 +271,31 @@ def self.name
 
 end
 
+class SlugLimitTest < TestCaseClass
+
+  include FriendlyId::Test
+
+  class Journalist < ActiveRecord::Base
+    extend FriendlyId
+    friendly_id :name, :use => :slugged, :slug_limit => 40
+  end
+
+  def model_class
+    Journalist
+  end
+
+  test "should limit slug size" do
+    transaction do
+      m1 = model_class.create! :name => 'a' * 50
+      assert_equal m1.slug, 'a' * 40
+      m2 = model_class.create! :name => m1.name
+      m2.save!
+      # "aaa-<uid>"
+      assert_match(/\Aa{3}\-/, m2.slug)
+    end
+  end
+end
+
 class DefaultScopeTest < TestCaseClass
 
   include FriendlyId::Test
@@ -424,4 +449,4 @@ class Novel < ActiveRecord::Base
       assert_equal novel.id.to_s, novel.to_param
     end
   end
-end
+end