`WikiPage` should have a slug even when not persisted.

1. So we can build the markdown preview URL for it.

2. We can't skip the slug in this case, because the slug is used to
construct relative markdown URLs.

3. Add rspec feature tests to cover creating wiki pages with
   spaces/hyphens in the name.

4. Add rspec feature tests for markdown preview URL rewriting, which was
   only covered by unit tests up to this point.

app/models/wiki_page.rb

@@ -44,7 +44,11 @@ class WikiPage
 
   # The escaped URL path of this page.
   def slug
+    if @attributes[:slug].present?
       @attributes[:slug]
+    else
+      wiki.wiki.preview_page(title, '', format).url_path
+    end
   end
 
   alias_method :to_param, :slug

app/views/layouts/project.html.haml

@@ -5,7 +5,7 @@
 
 - content_for :scripts_body_top do
   - project = @target_project || @project
-  - if @project_wiki && @page && @page.slug.present?
+  - if @project_wiki && @page
     - markdown_preview_path = namespace_project_wiki_markdown_preview_path(project.namespace, project, @page.slug)
   - else
     - markdown_preview_path = markdown_preview_namespace_project_path(project.namespace, project)

spec/features/projects/wiki/markdown_preview_spec.rb

+require 'spec_helper'
+
+feature 'Projects > Wiki > User previews markdown changes', feature: true, js: true do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, namespace: user.namespace) }
+  let(:wiki_content) do
+    <<-HEREDOC
+[regular link](regular)
+[relative link 1](../relative)
+[relative link 2](./relative)
+[relative link 3](./e/f/relative)
+    HEREDOC
+  end
+
+  background do
+    project.team << [user, :master]
+    login_as(user)
+
+    visit namespace_project_path(project.namespace, project)
+    click_link 'Wiki'
+    WikiPages::CreateService.new(project, user, title: 'home', content: 'Home page').execute
+  end
+
+  context "while creating a new wiki page" do
+    context "when there are no spaces or hyphens in the page name" do
+      it "rewrites relative links as expected" do
+        click_link 'New Page'
+        fill_in :new_wiki_path, with: 'a/b/c/d'
+        click_button 'Create Page'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/c/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/c/e/f/relative\">relative link 3</a>")
+      end
+    end
+
+    context "when there are spaces in the page name" do
+      it "rewrites relative links as expected" do
+        click_link 'New Page'
+        fill_in :new_wiki_path, with: 'a page/b page/c page/d page'
+        click_button 'Create Page'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/e/f/relative\">relative link 3</a>")
+      end
+    end
+
+    context "when there are hyphens in the page name" do
+      it "rewrites relative links as expected" do
+        click_link 'New Page'
+        fill_in :new_wiki_path, with: 'a-page/b-page/c-page/d-page'
+        click_button 'Create Page'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/e/f/relative\">relative link 3</a>")
+      end
+    end
+  end
+
+  context "while editing a wiki page" do
+    def create_wiki_page(path)
+      click_link 'New Page'
+      fill_in :new_wiki_path, with: path
+      click_button 'Create Page'
+      fill_in :wiki_content, with: 'content'
+      click_on "Create page"
+    end
+
+    context "when there are no spaces or hyphens in the page name" do
+      it "rewrites relative links as expected" do
+        create_wiki_page 'a/b/c/d'
+        click_link 'Edit'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/c/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a/b/c/e/f/relative\">relative link 3</a>")
+      end
+    end
+
+    context "when there are spaces in the page name" do
+      it "rewrites relative links as expected" do
+        create_wiki_page 'a page/b page/c page/d page'
+        click_link 'Edit'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/e/f/relative\">relative link 3</a>")
+      end
+    end
+
+    context "when there are hyphens in the page name" do
+      it "rewrites relative links as expected" do
+        create_wiki_page 'a-page/b-page/c-page/d-page'
+        click_link 'Edit'
+
+        fill_in :wiki_content, with: wiki_content
+        click_on "Preview"
+
+        expect(page).to have_content("regular link")
+
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/regular\">regular link</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/relative\">relative link 1</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/relative\">relative link 2</a>")
+        expect(page.html).to include("<a href=\"/#{project.path_with_namespace}/wikis/a-page/b-page/c-page/e/f/relative\">relative link 3</a>")
+      end
+    end
+  end
+end

spec/features/projects/wiki/user_creates_wiki_page_spec.rb

@@ -30,7 +30,8 @@ feature 'Projects > Wiki > User creates wiki page', feature: true do
         WikiPages::CreateService.new(project, user, title: 'home', content: 'Home page').execute
       end
 
-      scenario 'via the "new wiki page" page', js: true do
+      context 'via the "new wiki page" page' do
+        scenario 'when the wiki page has a single word name', js: true do
           click_link 'New Page'
 
           fill_in :new_wiki_path, with: 'foo'
@@ -43,6 +44,35 @@ feature 'Projects > Wiki > User creates wiki page', feature: true do
           expect(page).to have_content("last edited by #{user.name}")
           expect(page).to have_content('My awesome wiki!')
         end
+
+        scenario 'when the wiki page has spaces in the name', js: true do
+          click_link 'New Page'
+
+          fill_in :new_wiki_path, with: 'Spaces in the name'
+          click_button 'Create Page'
+
+          fill_in :wiki_content, with: 'My awesome wiki!'
+          click_button 'Create page'
+
+          expect(page).to have_content('Spaces in the name')
+          expect(page).to have_content("last edited by #{user.name}")
+          expect(page).to have_content('My awesome wiki!')
+        end
+
+        scenario 'when the wiki page has hyphens in the name', js: true do
+          click_link 'New Page'
+
+          fill_in :new_wiki_path, with: 'hyphens-in-the-name'
+          click_button 'Create Page'
+
+          fill_in :wiki_content, with: 'My awesome wiki!'
+          click_button 'Create page'
+
+          expect(page).to have_content('Hyphens in the name')
+          expect(page).to have_content("last edited by #{user.name}")
+          expect(page).to have_content('My awesome wiki!')
+        end
+      end
     end
   end