Autolink package names in Gemfile

4 files changed, 176 insertions, 10 deletions

diff --git a/lib/gitlab/dependency_linker.rb b/lib/gitlab/dependency_linker.rb
new file mode 100644
index 00000000000..5e884c4bea1
--- /dev/null
+++ b/lib/gitlab/dependency_linker.rb
@@ -0,0 +1,18 @@
+module Gitlab
+  module DependencyLinker
+    LINKERS = [
+      GemfileLinker,
+    ].freeze
+
+    def self.linker(blob_name)
+      LINKERS.find { |linker| linker.support?(blob_name) }
+    end
+
+    def self.link(blob_name, plain_text, highlighted_text)
+      linker = linker(blob_name)
+      return highlighted_text unless linker
+
+      linker.link(plain_text, highlighted_text)
+    end
+  end
+end
diff --git a/lib/gitlab/dependency_linker/base_linker.rb b/lib/gitlab/dependency_linker/base_linker.rb
new file mode 100644
index 00000000000..40a4ad11372
--- /dev/null
+++ b/lib/gitlab/dependency_linker/base_linker.rb
@@ -0,0 +1,103 @@
+module Gitlab
+  module DependencyLinker
+    class BaseLinker
+      def self.link(plain_text, highlighted_text)
+        new(plain_text, highlighted_text).link
+      end
+
+      attr_accessor :plain_text, :highlighted_text
+
+      def initialize(plain_text, highlighted_text)
+        @plain_text = plain_text
+        @highlighted_text = highlighted_text
+      end
+
+      def link
+        link_dependencies
+
+        highlighted_lines.join.html_safe
+      end
+
+      private
+
+      def package_url(name)
+        raise NotImplementedError
+      end
+
+      def link_dependencies
+        raise NotImplementedError
+      end
+
+      def package_link(name, url = package_url(name))
+        return name unless url
+
+        %{<a href="#{ERB::Util.html_escape_once(url)}" rel="noopener noreferrer" target="_blank">#{ERB::Util.html_escape_once(name)}</a>}
+      end
+
+      # Links package names in a method call or assignment string argument.
+      #
+      # Example:
+      #   link_method_call("gem")
+      #   # Will link `package` in `gem "package"`, `gem("package")` and `gem = "package"`
+      #
+      #   link_method_call("gem", "specific_package")
+      #   # Will link `specific_package` in `gem "specific_package"`
+      #
+      #   link_method_call("github", /[^\/]+\/[^\/]+/)
+      #   # Will link `user/repo` in `github "user/repo"`, but not `github "package"`
+      #
+      #   link_method_call(%w[add_dependency add_development_dependency])
+      #   # Will link `spec.add_dependency "package"` and `spec.add_development_dependency "package"`
+      #
+      #   link_method_call("name")
+      #   # Will link `package` in `self.name = "package"`
+      def link_method_call(method_names, value = nil, &url_proc)
+        value =
+          case value
+          when String
+            Regexp.escape(value)
+          when nil
+            /[^'"]+/
+          else
+            value
+          end
+
+        method_names = Array(method_names).map { |name| Regexp.escape(name) }
+
+        regex = %r{
+          #{Regexp.union(method_names)} # Method name
+          \s*                           # Whitespace
+          [(=]?                         # Opening brace or equals sign
+          \s*                           # Whitespace
+          ['"](?<name>#{value})['"]     # Package name in quotes
+        }x
+
+        link_regex(regex, &url_proc)
+      end
+
+      # Links package names based on regex.
+      #
+      # Example:
+      #   link_regex(/(github:|:github =>)\s*['"](?<name>[^'"]+)['"]/)
+      #   # Will link `user/repo` in `github: "user/repo"` or `:github => "user/repo"`
+      def link_regex(regex)
+        highlighted_lines.map!.with_index do |rich_line, i|
+          marker = StringRegexMarker.new(plain_lines[i], rich_line.html_safe)
+
+          marker.mark(regex, group: :name) do |text, left:, right:|
+            url = block_given? ? yield(text) : package_url(text)
+            package_link(text, url)
+          end
+        end
+      end
+
+      def plain_lines
+        @plain_lines ||= plain_text.lines
+      end
+
+      def highlighted_lines
+        @highlighted_lines ||= highlighted_text.lines
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/dependency_linker/gemfile_linker.rb b/lib/gitlab/dependency_linker/gemfile_linker.rb
new file mode 100644
index 00000000000..e36b88d357d
--- /dev/null
+++ b/lib/gitlab/dependency_linker/gemfile_linker.rb
@@ -0,0 +1,28 @@
+module Gitlab
+  module DependencyLinker
+    class GemfileLinker < BaseLinker
+      def self.support?(blob_name)
+        blob_name == 'Gemfile' || blob_name == 'gems.rb'
+      end
+
+      private
+
+      def link_dependencies
+        # Link `gem "package_name"` to https://rubygems.org/gems/package_name
+        link_method_call("gem")
+
+        # Link `github: "user/repo"` to https://github.com/user/repo
+        link_regex(/(github:|:github\s*=>)\s*['"](?<name>[^'"]+)['"]/) do |name|
+          "https://github.com/#{name}"
+        end
+
+        # Link `source "https://rubygems.org"` to https://rubygems.org
+        link_method_call("source", %r{https?://[^'"]+}) { |url| url }
+      end
+
+      def package_url(name)
+        "https://rubygems.org/gems/#{name}"
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/highlight.rb b/lib/gitlab/highlight.rb
index d787d5db4a0..83bc230df3e 100644
--- a/lib/gitlab/highlight.rb
+++ b/lib/gitlab/highlight.rb
@@ -13,6 +13,8 @@ module Gitlab
       highlight(file_name, blob.data, repository: repository).lines.map!(&:html_safe)
     end
 
+    attr_reader :blob_name
+
     def initialize(blob_name, blob_content, repository: nil)
       @formatter = Rouge::Formatters::HTMLGitlab
       @repository = repository
@@ -21,16 +23,9 @@ module Gitlab
     end
 
     def highlight(text, continue: true, plain: false)
-      if plain
-        hl_lexer = Rouge::Lexers::PlainText
-        continue = false
-      else
-        hl_lexer = self.lexer
-      end
-
-      @formatter.format(hl_lexer.lex(text, continue: continue), tag: hl_lexer.tag).html_safe
-    rescue
-      @formatter.format(Rouge::Lexers::PlainText.lex(text)).html_safe
+      highlighted_text = highlight_text(text, continue: continue, plain: plain)
+      highlighted_text = link_dependencies(text, highlighted_text) if blob_name
+      highlighted_text
     end
 
     def lexer
@@ -50,5 +45,27 @@ module Gitlab
 
       Rouge::Lexer.find_fancy(language_name)
     end
+
+    def highlight_text(text, continue: true, plain: false)
+      if plain
+        highlight_plain(text)
+      else
+        highlight_rich(text, continue: continue)
+      end
+    end
+
+    def highlight_plain(text)
+      @formatter.format(Rouge::Lexers::PlainText.lex(text)).html_safe
+    end
+
+    def highlight_rich(text, continue: true)
+      @formatter.format(lexer.lex(text, continue: continue), tag: lexer.tag).html_safe
+    rescue
+      highlight_plain(text)
+    end
+
+    def link_dependencies(text, highlighted_text)
+      Gitlab::DependencyLinker.link(blob_name, text, highlighted_text)
+    end
   end
 end