fix total_pages, out_of_bounds? for empty collections

Fixes mislav#169

lib/will_paginate/active_record.rb

@@ -18,6 +18,8 @@ module WillPaginate
   module ActiveRecord
     # makes a Relation look like WillPaginate::Collection
     module RelationMethods
+      include WillPaginate::CollectionMethods
+
       attr_accessor :current_page
       attr_writer :total_entries, :wp_count_options
 
@@ -92,10 +94,6 @@ def empty?
         end
       end
 
-      def total_pages
-        (total_entries / limit_value.to_f).ceil
-      end
-
       def clone
         copy_will_paginate_data super
       end

lib/will_paginate/collection.rb

@@ -2,6 +2,38 @@
 require 'will_paginate/page_number'
 
 module WillPaginate
+  # Any will_paginate-compatible collection should have these methods:
+  #
+  #   current_page, per_page, offset, total_entries, total_pages
+  #
+  # It can also define some of these optional methods:
+  #
+  #   out_of_bounds?, previous_page, next_page
+  #
+  # This module provides few of these methods.
+  module CollectionMethods
+    def total_pages
+      total_entries.zero? ? 1 : (total_entries / per_page.to_f).ceil
+    end
+
+    # current_page - 1 or nil if there is no previous page
+    def previous_page
+      current_page > 1 ? (current_page - 1) : nil
+    end
+
+    # current_page + 1 or nil if there is no next page
+    def next_page
+      current_page < total_pages ? (current_page + 1) : nil
+    end
+
+    # Helper method that is true when someone tries to fetch a page with a
+    # larger number than the last page. Can be used in combination with flashes
+    # and redirecting.
+    def out_of_bounds?
+      current_page > total_pages
+    end
+  end
+
   # = The key to pagination
   # Arrays returned from paginating finds are, in fact, instances of this little
   # class. You may think of WillPaginate::Collection as an ordinary array with
@@ -18,7 +50,9 @@ module WillPaginate
   #   require 'will_paginate/collection'
   #   # WillPaginate::Collection is now available for use
   class Collection < Array
-    attr_reader :current_page, :per_page, :total_entries, :total_pages
+    include CollectionMethods
+
+    attr_reader :current_page, :per_page, :total_entries
 
     # Arguments to the constructor are the current page number, per-page limit
     # and the total number of entries. The last argument is optional because it
@@ -63,35 +97,16 @@ def self.create(page, per_page, total = nil)
       pager
     end
 
-    # Helper method that is true when someone tries to fetch a page with a
-    # larger number than the last page. Can be used in combination with flashes
-    # and redirecting.
-    def out_of_bounds?
-      current_page > total_pages
-    end
-
     # Current offset of the paginated collection. If we're on the first page,
     # it is always 0. If we're on the 2nd page and there are 30 entries per page,
     # the offset is 30. This property is useful if you want to render ordinals
     # side by side with records in the view: simply start with offset + 1.
     def offset
-      @current_page.to_offset(per_page).to_i
-    end
-
-    # current_page - 1 or nil if there is no previous page
-    def previous_page
-      current_page > 1 ? (current_page - 1) : nil
+      current_page.to_offset(per_page).to_i
     end
 
-    # current_page + 1 or nil if there is no next page
-    def next_page
-      current_page < total_pages ? (current_page + 1) : nil
-    end
-
-    # sets the <tt>total_entries</tt> property and calculates <tt>total_pages</tt>
     def total_entries=(number)
       @total_entries = number.to_i
-      @total_pages   = (@total_entries / per_page.to_f).ceil
     end
 
     # This is a magic wrapper for the original Array#replace method. It serves

lib/will_paginate/data_mapper.rb

@@ -30,6 +30,8 @@ def paginate(options)
     end
 
     module CollectionMethods
+      include WillPaginate::CollectionMethods
+
       attr_accessor :current_page
 
       def paginated?
@@ -58,10 +60,6 @@ def total_entries
         end
       end
 
-      def total_pages
-        (total_entries / per_page.to_f).ceil
-      end
-
       def to_a
         ::WillPaginate::Collection.create(current_page, per_page) do |col|
           col.replace super

lib/will_paginate/sequel.rb

@@ -1,10 +1,13 @@
 require 'sequel'
 require 'sequel/extensions/pagination'
+require 'will_paginate/collection'
 
 module WillPaginate
   # Sequel already supports pagination; we only need to make the
   # resulting dataset look a bit more like WillPaginate::Collection
   module SequelMethods
+    include WillPaginate::CollectionMethods
+
     def total_pages
       page_count
     end

spec/collection_spec.rb

@@ -71,12 +71,20 @@
     end
   end
 
-  it "should show out of bounds when page number is too high" do
-    create(2, 3, 2).should be_out_of_bounds
-  end
-
-  it "should not show out of bounds when inside collection" do
-    create(1, 3, 2).should_not be_out_of_bounds
+  describe "out of bounds" do
+    it "is out of bounds when page number is too high" do
+      create(2, 3, 2).should be_out_of_bounds
+    end
+
+    it "isn't out of bounds when inside collection" do
+      create(1, 3, 2).should_not be_out_of_bounds
+    end
+
+    it "isn't out of bounds when the collection is empty" do
+      collection = create(1, 3, 0)
+      collection.should_not be_out_of_bounds
+      collection.total_pages.should == 1
+    end
   end
 
   describe "guessing total count" do

spec/finders/active_record_spec.rb

@@ -179,6 +179,10 @@
     it "should count with group" do
       Developer.group(:salary).page(1).total_entries.should == 4
     end
+
+    it "should not have zero total_pages when the result set is empty" do
+      Developer.where("1 = 2").page(1).total_pages.should == 1
+    end
   end
 
   it "should not ignore :select parameter when it says DISTINCT" do

spec/finders/data_mapper_spec.rb

@@ -76,4 +76,8 @@
     Animal.all(:limit => 2).page(2).per_page.should == 2
   end
 
+  it "has total_pages at 1 for empty collections" do
+    Animal.all(:conditions => ['1=2']).page(1).total_pages.should == 1
+  end
+
 end if datamapper_loaded