Copying a rendered issue/comment will paste into GFM textareas as actual GFM

app/assets/javascripts/copy_as_gfm.js.es6

+/* eslint-disable class-methods-use-this */
+
+(() => {
+  const gfmRules = {
+    // Should have an entry for every filter in lib/banzai/pipeline/gfm_pipeline.rb,
+    // in reverse order.
+    // Should have test coverage in spec/features/copy_as_gfm_spec.rb.
+    "InlineDiffFilter": {
+      "span.idiff.addition": function(el, text) {
+        return "{+" + text + "+}";
+      },
+      "span.idiff.deletion": function(el, text) {
+        return "{-" + text + "-}";
+      },
+    },
+    "TaskListFilter": {
+      "input[type=checkbox].task-list-item-checkbox": function(el, text) {
+        return '[' + (el.checked ? 'x' : ' ') + ']';
+      }
+    },
+    "ReferenceFilter": {
+      "a.gfm:not([data-link=true])": function(el, text) {
+        return el.getAttribute('data-original') || text;
+      },
+    },
+    "AutolinkFilter": {
+      "a": function(el, text) {
+        if (text != el.getAttribute("href")) {
+          // Fall back to handler for MarkdownFilter
+          return false;
+        }
+
+        return text;
+      },
+    },
+    "TableOfContentsFilter": {
+      "ul.section-nav": function(el, text) {
+        return "[[_TOC_]]";
+      },
+    },
+    "EmojiFilter": {
+      "img.emoji": function(el, text) {
+        return el.getAttribute("alt");
+      },
+    },
+    "ImageLinkFilter": {
+      "a.no-attachment-icon": function(el, text) {
+        return text;
+      },
+    },
+    "VideoLinkFilter": {
+      ".video-container": function(el, text) {
+        var videoEl = el.querySelector('video');
+        if (!videoEl) {
+          return false;
+        }
+
+        return CopyAsGFM.nodeToGFM(videoEl);
+      },
+      "video": function(el, text) {
+        return "![" + el.getAttribute('data-title') + "](" + el.getAttribute("src") + ")";
+      },
+    },
+    "MathFilter": {
+      "pre.code.math[data-math-style='display']": function(el, text) {
+        return "```math\n" + text.trim() + "\n```";
+      },
+      "code.code.math[data-math-style='inline']": function(el, text) {
+        return "$`" + text + "`$";
+      },
+      "span.katex-display span.katex-mathml": function(el, text) {
+        var mathAnnotation = el.querySelector('annotation[encoding="application/x-tex"]');
+        if (!mathAnnotation) {
+          return false;
+        }
+
+        return "```math\n" + CopyAsGFM.nodeToGFM(mathAnnotation)  + "\n```";
+      },
+      "span.katex-mathml": function(el, text) {
+        var mathAnnotation = el.querySelector('annotation[encoding="application/x-tex"]');
+        if (!mathAnnotation) {
+          return false;
+        }
+
+        return "$`" + CopyAsGFM.nodeToGFM(mathAnnotation) + "`$";
+      },
+      "span.katex-html": function(el, text) {
+        return "";
+      },
+      'annotation[encoding="application/x-tex"]': function(el, text) {
+        return text.trim();
+      }
+    },
+    "SyntaxHighlightFilter": {
+      "pre.code.highlight": function(el, text) {
+        var lang = el.getAttribute("lang");
+        if (lang == "text") {
+          lang = "";
+        }
+        return "```" + lang + "\n" + text.trim() + "\n```";
+      },
+      "pre > code": function(el, text) {
+         // Don't wrap code blocks in ``
+        return text;
+      },
+    },
+    "MarkdownFilter": {
+      "code": function(el, text) {
+        var backtickCount = 1;
+        var backtickMatch = text.match(/`+/);
+        if (backtickMatch) {
+          backtickCount = backtickMatch[0].length + 1;
+        }
+
+        var backticks = new Array(backtickCount + 1).join('`');
+        var spaceOrNoSpace = backtickCount > 1 ? " " : "";
+
+        return backticks + spaceOrNoSpace + text + spaceOrNoSpace + backticks;
+      },
+      "blockquote": function(el, text) {
+        return text.trim().split('\n').map(function(s) { return ('> ' + s).trim(); }).join('\n');
+      },
+      "img": function(el, text) {
+        return "![" + el.getAttribute("alt") + "](" + el.getAttribute("src") + ")";
+      },
+      "a.anchor": function(el, text) {
+        return text;
+      },
+      "a": function(el, text) {
+        return "[" + text + "](" + el.getAttribute("href") + ")";
+      },
+      "li": function(el, text) {
+        var lines = text.trim().split('\n');
+        var firstLine = '- ' + lines.shift();
+        var nextLines = lines.map(function(s) { return ('  ' + s).replace(/\s+$/, ''); });
+
+        return firstLine + '\n' + nextLines.join('\n');
+      },
+      "ul": function(el, text) {
+        return text;
+      },
+      "ol": function(el, text) {
+        return text.replace(/^- /mg, '1. ');
+      },
+      "h1": function(el, text) {
+        return '# ' + text.trim();
+      },
+      "h2": function(el, text) {
+        return '## ' + text.trim();
+      },
+      "h3": function(el, text) {
+        return '### ' + text.trim();
+      },
+      "h4": function(el, text) {
+        return '#### ' + text.trim();
+      },
+      "h5": function(el, text) {
+        return '##### ' + text.trim();
+      },
+      "h6": function(el, text) {
+        return '###### ' + text.trim();
+      },
+      "strong": function(el, text) {
+        return '**' + text + '**';
+      },
+      "em": function(el, text) {
+        return '_' + text + '_';
+      },
+      "del": function(el, text) {
+        return '~~' + text + '~~';
+      },
+      "sup": function(el, text) {
+        return '^' + text;
+      },
+      "hr": function(el, text) {
+        return '-----';
+      },
+      "table": function(el, text) {
+        var theadText = CopyAsGFM.nodeToGFM(el.querySelector('thead'));
+        var tbodyText = CopyAsGFM.nodeToGFM(el.querySelector('tbody'));
+
+        return theadText + tbodyText;
+      },
+      "thead": function(el, text) {
+        var cells = _.map(el.querySelectorAll('th'), function(cell) {
+          var chars = CopyAsGFM.nodeToGFM(cell).trim().length;
+
+          var before = '';
+          var after = '';
+          switch (cell.style.textAlign) {
+            case 'center':
+              before = ':';
+              after = ':';
+              chars -= 2;
+              break;
+            case 'right':
+              after = ':';
+              chars -= 1;
+              break;
+          }
+
+          chars = Math.max(chars, 0);
+
+          var middle = new Array(chars + 1).join('-');
+
+          return before + middle + after;
+        });
+        return text + '| ' + cells.join(' | ') + ' |';
+      },
+      "tr": function(el, text) {
+        var cells = _.map(el.querySelectorAll('td, th'), function(cell) {
+          return CopyAsGFM.nodeToGFM(cell).trim();
+        });
+        return '| ' + cells.join(' | ') + ' |';
+      },
+    }
+  };
+
+  class CopyAsGFM {
+    constructor() {
+      $(document).on('copy', '.md, .wiki', this.handleCopy.bind(this));
+      $(document).on('paste', '.js-gfm-input', this.handlePaste.bind(this));
+    }
+
+    handleCopy(e) {
+      var clipboardData = e.originalEvent.clipboardData;
+      if (!clipboardData) return;
+
+      if (!window.getSelection) return;
+
+      var selection = window.getSelection();
+      if (!selection.rangeCount || selection.rangeCount === 0) return;
+
+      var selectedDocument = selection.getRangeAt(0).cloneContents();
+      if (!selectedDocument) return;
+
+      e.preventDefault();
+      clipboardData.setData('text/plain', selectedDocument.textContent);
+
+      var gfm = CopyAsGFM.nodeToGFM(selectedDocument);
+      clipboardData.setData('text/x-gfm', gfm);
+    }
+
+    handlePaste(e) {
+      var clipboardData = e.originalEvent.clipboardData;
+      if (!clipboardData) return;
+      
+      var gfm = clipboardData.getData('text/x-gfm');
+      if (!gfm) return;
+
+      e.preventDefault();
+
+      this.insertText(e.target, gfm);
+    }
+
+    insertText(target, text) {
+      // Firefox doesn't support `document.execCommand('insertText', false, text);` on textareas
+      var selectionStart = target.selectionStart;
+      var selectionEnd = target.selectionEnd;
+      var value = target.value;
+      var textBefore = value.substring(0, selectionStart);
+      var textAfter  = value.substring(selectionEnd, value.length);
+      var newText = textBefore + text + textAfter;
+      target.value = newText;
+      target.selectionStart = target.selectionEnd = selectionStart + text.length;
+    }
+
+    static nodeToGFM(node) {
+      if (node.nodeType == Node.TEXT_NODE) {
+        return node.textContent;
+      }
+
+      var text = this.innerGFM(node);
+
+      if (node.nodeType == Node.DOCUMENT_FRAGMENT_NODE) {
+        return text;
+      }
+
+      for (var filter in gfmRules) {
+        var rules = gfmRules[filter];
+
+        for (var selector in rules) {
+          var func = rules[selector];
+
+          if (!node.matches(selector)) continue;
+
+          var result = func(node, text);
+          if (result === false) continue;
+
+          return result;
+        }
+      }
+
+      return text;
+    }
+
+    static innerGFM(parentNode) {
+      var nodes = parentNode.childNodes;
+
+      var clonedParentNode = parentNode.cloneNode(true);
+      var clonedNodes = Array.prototype.slice.call(clonedParentNode.childNodes, 0);
+
+      for (var i = 0; i < nodes.length; i++) {
+        var node = nodes[i];
+        var clonedNode = clonedNodes[i];
+
+        var text = this.nodeToGFM(node);
+        clonedNode.parentNode.replaceChild(document.createTextNode(text), clonedNode);
+      }
+
+      return clonedParentNode.innerText || clonedParentNode.textContent;
+    }
+  }
+
+  window.gl = window.gl || {};
+  window.gl.CopyAsGFM = CopyAsGFM;
+
+  new CopyAsGFM();
+})();

app/assets/javascripts/shortcuts_issuable.js

@@ -39,29 +39,33 @@
     }
 
     ShortcutsIssuable.prototype.replyWithSelectedText = function() {
-      var quote, replyField, selected, separator;
-      if (window.getSelection) {
-        selected = window.getSelection().toString();
-        replyField = $('.js-main-target-form #note_note');
-        if (selected.trim() === "") {
-          return;
-        }
-        // Put a '>' character before each non-empty line in the selection
-        quote = _.map(selected.split("\n"), function(val) {
-          if (val.trim() !== '') {
-            return "> " + val + "\n";
-          }
-        });
-        // If replyField already has some content, add a newline before our quote
-        separator = replyField.val().trim() !== "" && "\n" || '';
-        replyField.val(function(_, current) {
-          return current + separator + quote.join('') + "\n";
-        });
-        // Trigger autosave for the added text
-        replyField.trigger('input');
-        // Focus the input field
-        return replyField.focus();
+      var quote, replyField, selectedDocument, selected, selection, separator;
+      if (!window.getSelection) return;
+
+      selection = window.getSelection();
+      if (!selection.rangeCount || selection.rangeCount === 0) return;
+
+      selectedDocument = selection.getRangeAt(0).cloneContents();
+      if (!selectedDocument) return;
+
+      selected = window.gl.CopyAsGFM.nodeToGFM(selectedDocument);
+
+      replyField = $('.js-main-target-form #note_note');
+      if (selected.trim() === "") {
+        return;
       }
+      quote = _.map(selected.split("\n"), function(val) {
+        return "> " + val + "\n";
+      });
+      // If replyField already has some content, add a newline before our quote
+      separator = replyField.val().trim() !== "" && "\n" || '';
+      replyField.val(function(_, current) {
+        return current + separator + quote.join('') + "\n";
+      });
+      // Trigger autosave for the added text
+      replyField.trigger('input');
+      // Focus the input field
+      return replyField.focus();
     };
 
     ShortcutsIssuable.prototype.editIssue = function() {

changelogs/unreleased/copy-as-md.yml

+---
+title: Copying a rendered issue/comment will paste into GFM textareas as actual GFM
+merge_request:
+author:

lib/banzai/filter/abstract_reference_filter.rb

@@ -153,7 +153,7 @@ module Banzai
             title = object_link_title(object)
             klass = reference_class(object_sym)
 
-            data = data_attributes_for(link_content || match, project, object)
+            data = data_attributes_for(link_content || match, project, object, link: !!link_content)
 
             if matches.names.include?("url") && matches[:url]
               url = matches[:url]
@@ -172,9 +172,10 @@ module Banzai
         end
       end
 
-      def data_attributes_for(text, project, object)
+      def data_attributes_for(text, project, object, link: false)
         data_attribute(
           original:     text,
+          link:         link,
           project:      project.id,
           object_sym => object.id
         )

lib/banzai/filter/issue_reference_filter.rb

@@ -62,7 +62,7 @@ module Banzai
         end
       end
 
-      def data_attributes_for(text, project, object)
+      def data_attributes_for(text, project, object, link: false)
         if object.is_a?(ExternalIssue)
           data_attribute(
             project: project.id,

lib/banzai/filter/syntax_highlight_filter.rb

@@ -20,17 +20,18 @@ module Banzai
         code = node.text
         css_classes = "code highlight"
         lexer = lexer_for(language)
+        lang = lexer.tag
 
         begin
           code = format(lex(lexer, code))
 
-          css_classes << " js-syntax-highlight #{lexer.tag}"
+          css_classes << " js-syntax-highlight #{lang}"
         rescue
           # Gracefully handle syntax highlighter bugs/errors to ensure
           # users can still access an issue/comment/etc.
         end
 
-        highlighted = %(<pre class="#{css_classes}" v-pre="true"><code>#{code}</code></pre>)
+        highlighted = %(<pre class="#{css_classes}" lang="#{lang}" v-pre="true"><code>#{code}</code></pre>)
 
         # Extracted to a method to measure it
         replace_parent_pre_element(node, highlighted)

lib/banzai/filter/video_link_filter.rb

@@ -35,7 +35,8 @@ module Banzai
           src: element['src'],
           width: '400',
           controls: true,
-          'data-setup' => '{}')
+          'data-setup' => '{}',
+          'data-title' => element['title'] || element['alt'])
 
         link = doc.document.create_element(
           'a',

lib/banzai/pipeline/gfm_pipeline.rb

 module Banzai
   module Pipeline
     class GfmPipeline < BasePipeline
+      # Every filter should have an entry in app/assets/javascripts/copy_as_gfm.js.es6,
+      # in reverse order.
+      # Should have test coverage in spec/features/copy_as_gfm_spec.rb.
       def self.filters
         @filters ||= FilterArray[
           Filter::SyntaxHighlightFilter,

spec/features/copy_as_gfm_spec.rb

+require 'spec_helper'
+
+describe 'Copy as GFM', feature: true, js: true do
+  include GitlabMarkdownHelper
+  include ActionView::Helpers::JavaScriptHelper
+
+  before do
+    @feat = MarkdownFeature.new
+
+    # `markdown` helper expects a `@project` variable
+    @project = @feat.project
+
+    visit namespace_project_issue_path(@project.namespace, @project, @feat.issue)
+  end
+
+  # Should have an entry for every filter in lib/banzai/pipeline/gfm_pipeline.rb
+  # and app/assets/javascripts/copy_as_gfm.js.es6
+  filters = {
+    'any filter' => [
+      [
+        'crazy nesting',
+        '> 1. [x] **[$`2 + 2`$ {-=-}{+=+} 2^2 ~~:thumbsup:~~](http://google.com)**'
+      ],
+      [
+        'real world example from the gitlab-ce README',
+        <<-GFM.strip_heredoc
+          # GitLab
+
+          [![Build status](https://gitlab.com/gitlab-org/gitlab-ce/badges/master/build.svg)](https://gitlab.com/gitlab-org/gitlab-ce/commits/master)
+          [![CE coverage report](https://gitlab.com/gitlab-org/gitlab-ce/badges/master/coverage.svg?job=coverage)](https://gitlab-org.gitlab.io/gitlab-ce/coverage-ruby)
+          [![Code Climate](https://codeclimate.com/github/gitlabhq/gitlabhq.svg)](https://codeclimate.com/github/gitlabhq/gitlabhq)
+          [![Core Infrastructure Initiative Best Practices](https://bestpractices.coreinfrastructure.org/projects/42/badge)](https://bestpractices.coreinfrastructure.org/projects/42)
+
+          ## Canonical source
+
+          The canonical source of GitLab Community Edition is [hosted on GitLab.com](https://gitlab.com/gitlab-org/gitlab-ce/).
+
+          ## Open source software to collaborate on code
+
+          To see how GitLab looks please see the [features page on our website](https://about.gitlab.com/features/).
+
+
+          - Manage Git repositories with fine grained access controls that keep your code secure
+
+          - Perform code reviews and enhance collaboration with merge requests
+
+          - Complete continuous integration (CI) and CD pipelines to builds, test, and deploy your applications
+
+          - Each project can also have an issue tracker, issue board, and a wiki
+
+          - Used by more than 100,000 organizations, GitLab is the most popular solution to manage Git repositories on-premises
+
+          - Completely free and open source (MIT Expat license)
+        GFM
+      ]
+    ],
+    'InlineDiffFilter' => [
+      '{-Deleted text-}',
+      '{+Added text+}'
+    ],
+    'TaskListFilter' => [
+      '- [ ] Unchecked task',
+      '- [x] Checked task',
+      '1. [ ] Unchecked numbered task',
+      '1. [x] Checked numbered task'
+    ],
+    'ReferenceFilter' => [
+      ['issue reference', -> { @feat.issue.to_reference }],
+      ['full issue reference', -> { @feat.issue.to_reference(full: true) }],
+      ['issue URL', -> { namespace_project_issue_url(@project.namespace, @project, @feat.issue) }],
+      ['issue URL with note anchor', -> { namespace_project_issue_url(@project.namespace, @project, @feat.issue, anchor: 'note_123') }],
+      ['issue link', -> { "[Issue](#{namespace_project_issue_url(@project.namespace, @project, @feat.issue)})" }],
+      ['issue link with note anchor', -> { "[Issue](#{namespace_project_issue_url(@project.namespace, @project, @feat.issue, anchor: 'note_123')})" }],
+    ],
+    'AutolinkFilter' => [
+      'https://example.com'
+    ],
+    'TableOfContentsFilter' => [
+      '[[_TOC_]]'
+    ],
+    'EmojiFilter' => [
+      ':thumbsup:'
+    ],
+    'ImageLinkFilter' => [
+      '![Image](https://example.com/image.png)'
+    ],
+    'VideoLinkFilter' => [
+      '![Video](https://example.com/video.mp4)'
+    ],
+    'MathFilter' => [
+      '$`c = \pm\sqrt{a^2 + b^2}`$',
+      [
+        'math block',
+        <<-GFM.strip_heredoc
+          ```math
+          c = \pm\sqrt{a^2 + b^2}
+          ```
+        GFM
+      ]
+    ],
+    'SyntaxHighlightFilter' => [
+      [
+        'code block',
+        <<-GFM.strip_heredoc
+          ```ruby
+          def foo
+            bar
+          end
+          ```
+        GFM
+      ]
+    ],
+    'MarkdownFilter' => [
+      '`code`',
+      '`` code with ` ticks ``',
+
+      '> Quote',
+      [
+        'multiline quote',
+        <<-GFM.strip_heredoc,
+          > Multiline
+          > Quote
+          >
+          > With multiple paragraphs
+        GFM
+      ],
+
+      '![Image](https://example.com/image.png)',
+
+      '# Heading with no anchor link',
+
+      '[Link](https://example.com)',
+
+      '- List item',
+      [
+        'multiline list item',
+        <<-GFM.strip_heredoc,
+          - Multiline
+            List item
+        GFM
+      ],
+      [
+        'nested lists',
+        <<-GFM.strip_heredoc,
+          - Nested
+
+
+            - Lists
+        GFM
+      ],
+      '1. Numbered list item',
+      [
+        'multiline numbered list item',
+        <<-GFM.strip_heredoc,
+          1. Multiline
+            Numbered list item
+        GFM
+      ],
+      [
+        'nested numbered list',
+        <<-GFM.strip_heredoc,
+          1. Nested
+
+
+            1. Numbered lists
+        GFM
+      ],
+
+      '# Heading',
+      '## Heading',
+      '### Heading',
+      '#### Heading',
+      '##### Heading',
+      '###### Heading',
+
+      '**Bold**',
+
+      '_Italics_',
+
+      '~~Strikethrough~~',
+
+      '2^2',
+
+      '-----',
+
+      [
+        'table',
+        <<-GFM.strip_heredoc,
+          | Centered | Right | Left |
+          | :------: | ----: | ---- |
+          | Foo | Bar | **Baz** |
+          | Foo | Bar | **Baz** |
+        GFM
+      ]
+    ]
+  }
+
+  filters.each do |filter, examples|
+    context filter do
+      examples.each do |ex|
+        if ex.is_a?(String)
+          desc = "'#{ex}'"
+          gfm = ex
+        else
+          desc, gfm = ex
+        end
+
+        it "transforms #{desc} to HTML and back to GFM" do
+          gfm = instance_exec(&gfm) if gfm.is_a?(Proc)
+
+          html = markdown(gfm)
+          gfm2 = html_to_gfm(html)
+          expect(gfm2.strip).to eq(gfm.strip)
+        end
+      end
+    end
+  end
+
+  def html_to_gfm(html)
+    js = <<-JS.strip_heredoc
+      (function(html) {
+        var node = document.createElement('div');
+        node.innerHTML = html;
+        return window.gl.CopyAsGFM.nodeToGFM(node);
+      })("#{escape_javascript(html)}")
+    JS
+    page.evaluate_script(js)
+  end
+
+  # Fake a `current_user` helper
+  def current_user
+    @feat.user
+  end
+end