Merge branch '16568-relative-links-wiki-regression' into 'master'

Relative Links in the Wiki Are Broken

- [ ] #16568 (!4050) Relative links in wiki are broken
    - [x] Investigate issue

  
    - [x] Implementation / Fix

        - [x] Write (failing) tests for `WikiLinkFilter`
        - [x] Link to `./bar` should either get rewritten correctly or left alone
        - [x] Link to `./bar.md` should maybe get rewritten correctly (is left alone currently)
        - [x] Link to `bar.md` should get rewritten correctly


            - [x] Check if this indeed a bug

    - [x] Make sure CI is green
    - [x] Assign to endboss

    - [x] Wait for review

    - [x] Implement review feedback
    - [ ] Wait for merge


See merge request !4050

3 files changed, 140 insertions, 3 deletions

diff --git a/CHANGELOG b/CHANGELOG
index a89af7f4da0..650efcbf8f1 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,52 @@
 Please view this file on the master branch, on stable branches it's out of date.
 
+v 8.8.0 (unreleased)
+  - Snippets tab under user profile. !4001 (Long Nguyen)
+  - Fix error when using link to uploads in global snippets
+  - Assign labels and milestone to target project when moving issue. !3934 (Long Nguyen)
+  - Use a case-insensitive comparison in sanitizing URI schemes
+  - Project#open_branches has been cleaned up and no longer loads entire records into memory.
+  - Escape HTML in commit titles in system note messages
+  - Improve multiple branch push performance by memoizing permission checking
+  - Log to application.log when an admin starts and stops impersonating a user
+  - Updated gitlab_git to 10.1.0
+  - GitAccess#protected_tag? no longer loads all tags just to check if a single one exists
+  - Reduce delay in destroying a project from 1-minute to immediately
+  - Make build status canceled if any of the jobs was canceled and none failed
+  - Upgrade Sidekiq to 4.1.2
+  - Sanitize repo paths in new project error message
+  - Bump mail_room to 0.7.0 to fix stuck IDLE connections
+  - Remove future dates from contribution calendar graph.
+  - Support e-mail notifications for comments on project snippets
+  - Use ActionDispatch Remote IP for Akismet checking
+  - Fix error when visiting commit builds page before build was updated
+  - Add 'l' shortcut to open Label dropdown on issuables and 'i' to create new issue on a project
+  - Update SVG sanitizer to conform to SVG 1.1
+  - Speed up push emails with multiple recipients by only generating the email once
+  - Updated search UI
+  - Display informative message when new milestone is created
+  - Sanitize milestones and labels titles
+  - Support multi-line tag messages. !3833 (Calin Seciu)
+  - Allow "NEWS" and "CHANGES" as alternative names for CHANGELOG. !3768 (Connor Shea)
+  - Added button to toggle whitespaces changes on diff view
+  - Backport GitHub Enterprise import support from EE
+  - Create tags using Rugged for performance reasons. !3745
+  - API: Expose Issue#user_notes_count. !3126 (Anton Popov)
+  - Files over 5MB can only be viewed in their raw form, files over 1MB without highlighting !3718
+  - Add support for supressing text diffs using .gitattributes on the default branch (Matt Oakes)
+  - Add eager load paths to help prevent dependency load issues in Sidekiq workers. !3724
+  - Added multiple colors for labels in dropdowns when dups happen.
+  - Improve description for the Two-factor Authentication sign-in screen. (Connor Shea)
+  - API support for the 'since' and 'until' operators on commit requests (Paco Guzman)
+  - Fix Gravatar hint in user profile when Gravatar is disabled. !3988 (Artem Sidorenko)
+  - Expire repository exists? and has_visible_content? caches after a push if necessary
+  - Fix unintentional filtering bug in issues sorted by milestone due (Takuya Noguchi)
+  - Fix adding a todo for private group members (Ahmad Sherif)
+  - Bump ace-rails-ap gem version from 2.0.1 to 4.0.2 which upgrades Ace Editor from 1.1.2 to 1.2.3
+
+v 8.7.5
+  - Fix relative links in wiki pages. !4050
+
 v 8.7.4
   - Links for Redmine issue references are generated correctly again !4048 (Benedikt Huss)
   - Fix setting trusted proxies !3970
diff --git a/lib/banzai/filter/wiki_link_filter.rb b/lib/banzai/filter/wiki_link_filter.rb
index 06d10c98501..7dc771afd71 100644
--- a/lib/banzai/filter/wiki_link_filter.rb
+++ b/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
diff --git a/spec/lib/banzai/filter/wiki_link_filter_spec.rb b/spec/lib/banzai/filter/wiki_link_filter_spec.rb
new file mode 100644
index 00000000000..185abbb2108
--- /dev/null
+++ b/spec/lib/banzai/filter/wiki_link_filter_spec.rb
@@ -0,0 +1,85 @@
+require 'spec_helper'
+
+describe Banzai::Filter::WikiLinkFilter, lib: true do
+  include FilterSpecHelper
+
+  let(:namespace) { build_stubbed(:namespace, name: "wiki_link_ns") }
+  let(:project)   { build_stubbed(: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