fix(date): Correctly set date to nil in collections

lib/jekyll-algolia.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'jekyll/commands/algolia'
+require 'jekyll/algolia/overwrites'
 require 'date'
 
 module Jekyll
@@ -26,7 +27,6 @@ module Jekyll
     # The gist of the plugin works by instanciating a Jekyll site,
     # monkey-patching its `write` method and building it.
     def self.init(config = {})
-      @start_time = Time.now
       config = Configurator.init(config).config
       @site = Jekyll::Algolia::Site.new(config)
 
@@ -63,16 +63,6 @@ module Jekyll
       @site
     end
 
-    # Public: Get access to the time at which the command was run
-    #
-    # Jekyll will always set the updated time of pages to the time of the build
-    # run. The plugin needs those values to stay at nil if they did not change,
-    # so we'll keep track of the time at build time and revert any page build at
-    # that time to nil.
-    def self.start_time
-      @start_time
-    end
-
     # A Jekyll::Site subclass that overrides process from the parent class to
     # create JSON records out of rendered documents and push those records to
     # Algolia instead of writing files to disk.

lib/jekyll/algolia/file_browser.rb

@@ -216,26 +216,21 @@ module Jekyll
       #
       # file - The Jekyll file
       #
-      # All collections (including posts) will have a date taken either from the
-      # front-matter or the filename prefix. If none is set, Jekyll will use the
-      # current date.
-      #
-      # For pages, only dates defined in the front-matter will be used.
-      #
-      # Note that because the default date is the current one if none is
-      # defined, we have to make sure the date is actually nil when we index it.
-      # Otherwise the diff indexing mode will think that records have changed
-      # while they haven't.
+      # Posts have their date coming from the filepath, or the front-matter.
+      # Pages and other collection items can only have a date set in
+      # front-matter.
       def self.date(file)
-        date = file.data['date']
+        # Collections get their date from .date, while pages read it from .data.
+        # Jekyll by default will set the date of collection to the current date,
+        # but we overwrote this.
+        date = if file.respond_to?(:date)
+                 file.date
+               else
+                 file.data['date']
+               end
+
         return nil if date.nil?
-
-        # The date is *exactly* the time where the `jekyll algolia` was run.
-        # What a coincidence! It's a safe bet to assume that the original date
-        # was nil and has been overwritten by Jekyll
-        return nil if date.to_i == Jekyll::Algolia.start_time.to_i
-
-        date.to_i
+        date.to_time.to_i
       end
 
       # Public: Returns the raw excerpt of a file, directly as returned by

lib/jekyll/algolia/overwrites.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Jekyll
+  # Overwriting the Jekyll::Document class
+  class Document
+    # By default, Jekyll will set the current date (time of build) to any
+    # collection item. This will break our diff algorithm, so we monkey patch
+    # this call to return nil if no date is defined instead.
+    def date
+      data['date'] || nil
+    end
+  end
+end

spec/jekyll/algolia/file_browser_spec.rb

@@ -462,29 +462,44 @@ describe(Jekyll::Algolia::FileBrowser) do
   end
 
   describe '.date' do
-    subject { current.date(file) }
+    subject { current.date(site.__find_file(filepath)) }
 
-    context 'with a page in the root' do
-      let(:file) { site.__find_file('about.md') }
-      it { should eq nil }
-    end
-    context 'with a collection element with a date set in front-matter' do
-      let(:file) { site.__find_file('_my-collection/collection-item.html') }
-      it { should eq 452_469_600 }
-    end
-    context 'with a collection element with no date' do
-      let(:file) { site.__find_file('_my-collection/sample-item.md') }
-      it { should eq nil }
-    end
-    context 'with a post' do
-      let(:file) { site.__find_file('_posts/2015-07-02-test-post.md') }
-      it { should eq 1_435_788_000 }
+    context 'page' do
+      describe 'nothing in front matter' do
+        let(:filepath) { 'about.md' }
+        it { should eq nil }
+      end
+      describe 'date in front matter' do
+        let(:filepath) { 'front_matter.md' }
+        it { should eq 1_521_500_400 }
+      end
     end
 
-    context 'with a custom timezone' do
-      let(:site) { init_new_jekyll_site(timezone: 'America/New_York') }
-      let(:file) { site.__find_file('_posts/2015-07-02-test-post.md') }
-      it { should eq 1_435_809_600 }
+    context 'post' do
+      describe 'only date in filepath' do
+        let(:filepath) { 'post-with-date.md' }
+        it { should eq 1_521_414_000 }
+      end
+      describe 'date set in frontmatter' do
+        let(:filepath) { 'test-post.md' }
+        it { should eq 1_435_788_000 }
+      end
+      describe 'with a custom timezone' do
+        let(:site) { init_new_jekyll_site(timezone: 'America/New_York') }
+        let(:filepath) { 'test-post.md' }
+        it { should eq 1_435_809_600 }
+      end
+    end
+
+    context 'collection' do
+      describe 'no date defined' do
+        let(:filepath) { 'sample-item.md' }
+        it { should eq nil }
+      end
+      describe 'date in frontmatter' do
+        let(:filepath) { 'collection-item.md' }
+        it { should eq 452_469_600 }
+      end
     end
   end
 

spec/site/_my-collection/sample-item.md

@@ -2,7 +2,4 @@
 title: Sample item
 ---
 
-This collection item has no defined date. Jekyll will try to set the current
-date instead, but we need to keep it nil. If we don't the `diff` indexing mode
-will think that the item changed while it did not.
-
+This collection item has no defined date.

spec/site/_posts/2018-03-20-post-with-date.md

@@ -0,0 +1,7 @@
+---
+title: "Post with date"
+date: 2018-03-19
+---
+
+This post has a date set in the front matter different than the date set in the
+filename.

spec/site/front_matter.md

@@ -3,7 +3,7 @@ title: Front-matter test
 author: John Doe
 custom: foo
 slug: front_matter_test
-date: foo
+date: 2018-03-20
 tags: foo
 url: http://www.foo.com/
 type: foo