Add option to fail a build with front matter syntax errors (#5832)

Merge pull request 5832

docs/_docs/configuration.md

@@ -305,6 +305,18 @@ class="flag">flags</code> (specified on the command-line) that control them.
         <p><code class="flag">--profile</code></p>
       </td>
     </tr>
+    <tr class="setting">
+      <td>
+        <p class="name"><strong>Strict Front Matter</strong></p>
+        <p class="description">
+            Cause a build to fail if there is a YAML syntax error in a page's front matter.
+        </p>
+      </td>
+      <td class="align-center">
+        <p><code class="option">strict_front_matter: BOOL</code></p>
+        <p><code class="flag">--strict_front_matter</code></p>
+      </td>
+    </tr>
   </tbody>
 </table>
 </div>
@@ -607,6 +619,7 @@ exclude:      ["Gemfile", "Gemfile.lock", "node_modules", "vendor/bundle/", "ven
 keep_files:           [".git", ".svn"]
 encoding:             "utf-8"
 markdown_ext:         "markdown,mkdown,mkdn,mkd,md"
+strict_front_matter: false
 
 # Filtering Content
 show_drafts: null

lib/jekyll/command.rb

@@ -46,6 +46,7 @@ module Jekyll
       # c - the Jekyll::Command to add these options to
       #
       # Returns nothing
+      # rubocop:disable Metrics/MethodLength
       def add_build_options(c)
         c.option "config", "--config CONFIG_FILE[,CONFIG_FILE2,...]",
           Array, "Custom configuration file"
@@ -66,7 +67,10 @@ module Jekyll
         c.option "quiet", "-q", "--quiet", "Silence output."
         c.option "verbose", "-V", "--verbose", "Print verbose output."
         c.option "incremental", "-I", "--incremental", "Enable incremental rebuild."
+        c.option "strict_front_matter", "--strict_front_matter",
+          "Fail if errors are present in front matter"
       end
+      # rubocop:enable Metrics/MethodLength
     end
   end
 end

lib/jekyll/configuration.rb

@@ -24,6 +24,7 @@ module Jekyll
       "keep_files"          => [".git", ".svn"],
       "encoding"            => "utf-8",
       "markdown_ext"        => "markdown,mkdown,mkdn,mkd,md",
+      "strict_front_matter" => false,
 
       # Filtering Content
       "show_drafts"         => nil,

lib/jekyll/convertible.rb

@@ -48,8 +48,10 @@ module Jekyll
         end
       rescue SyntaxError => e
         Jekyll.logger.warn "YAML Exception reading #{filename}: #{e.message}"
+        raise e if self.site.config["strict_front_matter"]
       rescue => e
         Jekyll.logger.warn "Error reading file #{filename}: #{e.message}"
+        raise e if self.site.config["strict_front_matter"]
       end
 
       self.data ||= {}

lib/jekyll/document.rb

@@ -259,11 +259,8 @@ module Jekyll
           merge_defaults
           read_content(opts)
           read_post_data
-        rescue SyntaxError => e
-          Jekyll.logger.error "Error:", "YAML Exception reading #{path}: #{e.message}"
         rescue => e
-          raise e if e.is_a? Jekyll::Errors::FatalException
-          Jekyll.logger.error "Error:", "could not read file #{path}: #{e.message}"
+          handle_read_error(e)
         end
       end
     end
@@ -457,6 +454,19 @@ module Jekyll
       generate_excerpt
     end
 
+    private
+    def handle_read_error(error)
+      if error.is_a? SyntaxError
+        Jekyll.logger.error "Error:", "YAML Exception reading #{path}: #{error.message}"
+      else
+        Jekyll.logger.error "Error:", "could not read file #{path}: #{error.message}"
+      end
+
+      if site.config["strict_front_matter"] || error.is_a?(Jekyll::Errors::FatalException)
+        raise error
+      end
+    end
+
     private
     def populate_title
       if relative_path =~ DATE_FILENAME_MATCHER

test/source/_broken/bad_post.md

@@ -0,0 +1,4 @@
+---
+bad yaml: [
+---
+Real content starts here

test/test_convertible.rb

@@ -33,6 +33,14 @@ class TestConvertible < JekyllUnitTest
       assert_match(%r!#{File.join(@base, name)}!, out)
     end
 
+    should "raise for broken front matter with `strict_front_matter` set" do
+      name = "broken_front_matter2.erb"
+      @convertible.site.config["strict_front_matter"] = true
+      assert_raises do
+        @convertible.read_yaml(@base, name)
+      end
+    end
+
     should "not allow ruby objects in YAML" do
       out = capture_stderr do
         @convertible.read_yaml(@base, "exploit_front_matter.erb")

test/test_site.rb

@@ -280,6 +280,24 @@ class TestSite < JekyllUnitTest
           Site.new(site_configuration("destination" => File.join(source_dir, "..")))
         end
       end
+
+      should "raise for bad frontmatter if strict_front_matter is set" do
+        site = Site.new(site_configuration(
+          "collections"         => ["broken"],
+          "strict_front_matter" => true
+        ))
+        assert_raises do
+          site.process
+        end
+      end
+
+      should "not raise for bad frontmatter if strict_front_matter is not set" do
+        site = Site.new(site_configuration(
+          "collections"         => ["broken"],
+          "strict_front_matter" => false
+        ))
+        site.process
+      end
     end
 
     context "with orphaned files in destination" do