Document: throw a useful error when an invalid date is given

features/post_data.feature

@@ -39,6 +39,20 @@ Feature: Post data
     And the _site directory should exist
     And I should see "Post date: 27 Mar 2009" in "_site/2009/03/27/star-wars.html"
 
+  Scenario: Use post.date variable with invalid
+    Given I have a _posts directory
+    And I have a "_posts/2016-01-01-test.md" page with date "tuesday" that contains "I have a bad date."
+    When I run jekyll build
+    Then the _site directory should not exist
+    And I should see "Document '_posts/2016-01-01-test.md' does not have a valid date in the YAML front matter." in the build output
+
+  Scenario: Invalid date in filename
+    Given I have a _posts directory
+    And I have a "_posts/2016-22-01-test.md" page that contains "I have a bad date."
+    When I run jekyll build
+    Then the _site directory should not exist
+    And I should see "Document '_posts/2016-22-01-test.md' does not have a valid date in the filename." in the build output
+
   Scenario: Use post.id variable
     Given I have a _posts directory
     And I have a _layouts directory

lib/jekyll/document.rb

@@ -50,7 +50,7 @@ module Jekyll
     # Merge some data in with this document's data.
     #
     # Returns the merged data.
-    def merge_data!(other)
+    def merge_data!(other, source: "YAML front matter")
       if other.key?('categories') && !other['categories'].nil?
         if other['categories'].is_a?(String)
           other['categories'] = other['categories'].split(" ").map(&:strip)
@@ -61,7 +61,7 @@ module Jekyll
       if data.key?('date') && !data['date'].is_a?(Time)
         data['date'] = Utils.parse_date(
           data['date'].to_s,
-          "Document '#{relative_path}' does not have a valid date in the YAML front matter."
+          "Document '#{relative_path}' does not have a valid date in the #{source}."
         )
       end
       data
@@ -267,20 +267,23 @@ module Jekyll
       else
         begin
           defaults = @site.frontmatter_defaults.all(url, collection.label.to_sym)
-          merge_data!(defaults) unless defaults.empty?
+          merge_data!(defaults, source: "front matter defaults") unless defaults.empty?
 
           self.content = File.read(path, merged_file_read_opts(opts))
           if content =~ YAML_FRONT_MATTER_REGEXP
             self.content = $POSTMATCH
             data_file = SafeYAML.load(Regexp.last_match(1))
-            merge_data!(data_file) if data_file
+            merge_data!(data_file, source: "YAML front matter") if data_file
           end
 
           post_read
         rescue SyntaxError => e
-          puts "YAML Exception reading #{path}: #{e.message}"
+          Jekyll.logger.error "Error:", "YAML Exception reading #{path}: #{e.message}"
         rescue Exception => e
-          puts "Error reading file #{path}: #{e.message}"
+          if e.is_a? Jekyll::Errors::FatalException
+            raise e
+          end
+          Jekyll.logger.error "Error:", "could not read file #{path}: #{e.message}"
         end
       end
     end
@@ -291,9 +294,11 @@ module Jekyll
         merge_data!({
           "slug" => slug,
           "ext"  => ext
-        })
+        }, source: "filename")
-        merge_data!({ "date" => date }) if data['date'].nil? || data['date'].to_i == site.time.to_i
         data['title'] ||= slug.split('-').select(&:capitalize).join(' ')
+        if data['date'].nil? || data['date'].to_i == site.time.to_i
+          merge_data!({"date" => date}, source: "filename")
+        end
       end
       populate_categories
       populate_tags
@@ -312,7 +317,7 @@ module Jekyll
       superdirs = relative_path.sub(/#{special_dir}(.*)/, '').split(File::SEPARATOR).reject do |c|
         c.empty? || c.eql?(special_dir) || c.eql?(basename)
       end
-      merge_data!({ 'categories' => superdirs })
+      merge_data!({ 'categories' => superdirs }, source: "file path")
     end
 
     def populate_categories

lib/jekyll/site.rb

@@ -225,7 +225,7 @@ module Jekyll
       # Build a hash map based on the specified post attribute ( post attr =>
       # array of posts ) then sort each array in reverse order.
       hash = Hash.new { |h, key| h[key] = [] }
-      posts.docs.each { |p| p.data[post_attr].each { |t| hash[t] << p } }
+      posts.docs.each { |p| p.data[post_attr].each { |t| hash[t] << p } if p.data[post_attr] }
       hash.values.each { |posts| posts.sort!.reverse! }
       hash
     end