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Diffstat (limited to 'app/models/concerns/cache_markdown_field.rb')
-rw-r--r-- | app/models/concerns/cache_markdown_field.rb | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/app/models/concerns/cache_markdown_field.rb b/app/models/concerns/cache_markdown_field.rb new file mode 100644 index 00000000000..90bd6490a02 --- /dev/null +++ b/app/models/concerns/cache_markdown_field.rb @@ -0,0 +1,131 @@ +# This module takes care of updating cache columns for Markdown-containing +# fields. Use like this in the body of your class: +# +# include CacheMarkdownField +# cache_markdown_field :foo +# cache_markdown_field :bar +# cache_markdown_field :baz, pipeline: :single_line +# +# Corresponding foo_html, bar_html and baz_html fields should exist. +module CacheMarkdownField + # Knows about the relationship between markdown and html field names, and + # stores the rendering contexts for the latter + class FieldData + extend Forwardable + + def initialize + @data = {} + end + + def_delegators :@data, :[], :[]= + def_delegator :@data, :keys, :markdown_fields + + def html_field(markdown_field) + "#{markdown_field}_html" + end + + def html_fields + markdown_fields.map {|field| html_field(field) } + end + end + + # Dynamic registries don't really work in Rails as it's not guaranteed that + # every class will be loaded, so hardcode the list. + CACHING_CLASSES = %w[ + AbuseReport + Appearance + ApplicationSetting + BroadcastMessage + Issue + Label + MergeRequest + Milestone + Namespace + Note + Project + Release + Snippet + ] + + def self.caching_classes + CACHING_CLASSES.map(&:constantize) + end + + extend ActiveSupport::Concern + + included do + cattr_reader :cached_markdown_fields do + FieldData.new + end + + # Returns the default Banzai render context for the cached markdown field. + def banzai_render_context(field) + raise ArgumentError.new("Unknown field: #{field.inspect}") unless + cached_markdown_fields.markdown_fields.include?(field) + + # Always include a project key, or Banzai complains + project = self.project if self.respond_to?(:project) + context = cached_markdown_fields[field].merge(project: project) + + # Banzai is less strict about authors, so don't always have an author key + context[:author] = self.author if self.respond_to?(:author) + + context + end + + # Allow callers to look up the cache field name, rather than hardcoding it + def markdown_cache_field_for(field) + raise ArgumentError.new("Unknown field: #{field}") unless + cached_markdown_fields.markdown_fields.include?(field) + + cached_markdown_fields.html_field(field) + end + + # Always exclude _html fields from attributes (including serialization). + # They contain unredacted HTML, which would be a security issue + alias_method :attributes_before_markdown_cache, :attributes + def attributes + attrs = attributes_before_markdown_cache + + cached_markdown_fields.html_fields.each do |field| + attrs.delete(field) + end + + attrs + end + end + + class_methods do + private + + # Specify that a field is markdown. Its rendered output will be cached in + # a corresponding _html field. Any custom rendering options may be provided + # as a context. + def cache_markdown_field(markdown_field, context = {}) + raise "Add #{self} to CacheMarkdownField::CACHING_CLASSES" unless + CacheMarkdownField::CACHING_CLASSES.include?(self.to_s) + + cached_markdown_fields[markdown_field] = context + + html_field = cached_markdown_fields.html_field(markdown_field) + cache_method = "#{markdown_field}_cache_refresh".to_sym + invalidation_method = "#{html_field}_invalidated?".to_sym + + define_method(cache_method) do + html = Banzai::Renderer.cacheless_render_field(self, markdown_field) + __send__("#{html_field}=", html) + true + end + + # The HTML becomes invalid if any dependent fields change. For now, assume + # author and project invalidate the cache in all circumstances. + define_method(invalidation_method) do + changed_fields = changed_attributes.keys + invalidations = changed_fields & [markdown_field.to_s, "author", "project"] + !invalidations.empty? + end + + before_save cache_method, if: invalidation_method + end + end +end |