Add a spec for `WikiLinkFilter`

- And fix behavior for non-file hierarchical links.

lib/banzai/filter/wiki_link_filter.rb

@@ -25,7 +25,7 @@ module Banzai
       end
 
       def process_link_attr(html_attr)
-        return if html_attr.blank? || file_reference?(html_attr)
+        return if html_attr.blank? || file_reference?(html_attr) || hierarchical_link?(html_attr)
 
         uri = URI(html_attr.value)
         if uri.relative? && uri.path.present?
@@ -40,12 +40,17 @@ module Banzai
         uri
       end
 
+      def project_wiki
+        context[:project_wiki]
+      end
+
       def file_reference?(html_attr)
         !File.extname(html_attr.value).blank?
       end
 
-      def project_wiki
-        context[:project_wiki]
+      # Of the form `./link`, `../link`, or similar
+      def hierarchical_link?(html_attr)
+        html_attr.value[0] == '.'
       end
 
       def project_wiki_base_path

spec/lib/banzai/filter/wiki_link_filter_spec.rb

+require 'spec_helper'
+
+describe Banzai::Filter::WikiLinkFilter, lib: true do
+  include FilterSpecHelper
+
+  let(:namespace) { build(:namespace, name: "wiki_link_ns") }
+  let(:project)   { build(:empty_project, :public, name: "wiki_link_project", namespace: namespace) }
+  let(:user) { double }
+  let(:project_wiki) { ProjectWiki.new(project, user) }
+
+  describe "links within the wiki (relative)" do
+    describe "hierarchical links to the current directory" do
+      it "doesn't rewrite non-file links" do
+        link = "<a href='./page'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('./page')
+      end
+
+      it "doesn't rewrite file links" do
+        link = "<a href='./page.md'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('./page.md')
+      end
+    end
+
+    describe "hierarchical links to the parent directory" do
+      it "doesn't rewrite non-file links" do
+        link = "<a href='../page'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('../page')
+      end
+
+      it "doesn't rewrite file links" do
+        link = "<a href='../page.md'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('../page.md')
+      end
+    end
+
+    describe "hierarchical links to a sub-directory" do
+      it "doesn't rewrite non-file links" do
+        link = "<a href='./subdirectory/page'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('./subdirectory/page')
+      end
+
+      it "doesn't rewrite file links" do
+        link = "<a href='./subdirectory/page.md'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('./subdirectory/page.md')
+      end
+    end
+
+    describe "non-hierarchical links" do
+      it 'rewrites non-file links to be at the scope of the wiki root' do
+        link = "<a href='page'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+
+        expect(filtered_link.attribute('href').value).to match('/wiki_link_ns/wiki_link_project/wikis/page')
+      end
+
+      it "doesn't rewrite file links" do
+        link = "<a href='page.md'>Link to Page</a>"
+        filtered_link = filter(link, project_wiki: project_wiki).children[0]
+        expect(filtered_link.attribute('href').value).to eq('page.md')
+      end
+    end
+  end
+
+  describe "links outside the wiki (absolute)" do
+    it "doesn't rewrite links" do
+      link = "<a href='http://example.com/page'>Link to Page</a>"
+      filtered_link = filter(link, project_wiki: project_wiki).children[0]
+      expect(filtered_link.attribute('href').value).to eq('http://example.com/page')
+    end
+  end
+end