Issue #1848266 by alexpott: Convert Diff into a proper, PSR-0-compatible PHP component.

core/core.services.yml

@@ -114,6 +114,9 @@ services:
   cron:
     class: Drupal\Core\Cron
     arguments: ['@module_handler', '@lock', '@queue', '@state', '@current_user', '@session_manager']
+  diff.formatter:
+    class: Drupal\Core\Diff\DiffFormatter
+    arguments: ['@config.factory']
   database:
     class: Drupal\Core\Database\Connection
     factory_class: Drupal\Core\Database\Database

core/lib/Drupal/Component/Diff/Diff.php

+<?php
+
+namespace Drupal\Component\Diff;
+
+use Drupal\Component\Diff\Engine\DiffEngine;
+
+/**
+ * Class representing a 'diff' between two sequences of strings.
+ * @todo document
+ * @subpackage DifferenceEngine
+ *
+ * Copied from https://drupal.org/project/diff which was based PHP diff engine
+ * for phpwiki. (Taken from phpwiki-1.3.3) The original code in phpwiki was
+ * copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org> and
+ * licensed under GPL.
+ */
+class Diff {
+
+  /**
+   * The list of differences as an array of diff operations.
+   *
+   * @var \Drupal\Component\Diff\Engine\DiffOp[]
+   */
+  protected $edits;
+
+  /**
+   * Constructor.
+   * Computes diff between sequences of strings.
+   *
+   * @param $from_lines array An array of strings.
+   *      (Typically these are lines from a file.)
+   * @param $to_lines array An array of strings.
+   */
+  public function __construct($from_lines, $to_lines) {
+    $eng = new DiffEngine();
+    $this->edits = $eng->diff($from_lines, $to_lines);
+    //$this->_check($from_lines, $to_lines);
+  }
+
+  /**
+   * Compute reversed Diff.
+   *
+   * SYNOPSIS:
+   *
+   *  $diff = new Diff($lines1, $lines2);
+   *  $rev = $diff->reverse();
+   * @return object A Diff object representing the inverse of the
+   *          original diff.
+   */
+  public function reverse() {
+    $rev = $this;
+    $rev->edits = array();
+    foreach ($this->edits as $edit) {
+      $rev->edits[] = $edit->reverse();
+    }
+    return $rev;
+  }
+
+  /**
+   * Check for empty diff.
+   *
+   * @return bool True iff two sequences were identical.
+   */
+  public function isEmpty() {
+    foreach ($this->edits as $edit) {
+      if ($edit->type != 'copy') {
+        return FALSE;
+      }
+    }
+    return TRUE;
+  }
+
+  /**
+   * Compute the length of the Longest Common Subsequence (LCS).
+   *
+   * This is mostly for diagnostic purposed.
+   *
+   * @return int The length of the LCS.
+   */
+  public function lcs() {
+    $lcs = 0;
+    foreach ($this->edits as $edit) {
+      if ($edit->type == 'copy') {
+        $lcs += sizeof($edit->orig);
+      }
+    }
+    return $lcs;
+  }
+
+  /**
+   * Get the original set of lines.
+   *
+   * This reconstructs the $from_lines parameter passed to the
+   * constructor.
+   *
+   * @return array The original sequence of strings.
+   */
+  public function orig() {
+    $lines = array();
+
+    foreach ($this->edits as $edit) {
+      if ($edit->orig) {
+        array_splice($lines, sizeof($lines), 0, $edit->orig);
+      }
+    }
+    return $lines;
+  }
+
+  /**
+   * Get the closing set of lines.
+   *
+   * This reconstructs the $to_lines parameter passed to the
+   * constructor.
+   *
+   * @return array The sequence of strings.
+   */
+  public function closing() {
+    $lines = array();
+
+    foreach ($this->edits as $edit) {
+      if ($edit->closing) {
+        array_splice($lines, sizeof($lines), 0, $edit->closing);
+      }
+    }
+    return $lines;
+  }
+
+  /**
+   * Check a Diff for validity.
+   *
+   * This is here only for debugging purposes.
+   */
+  public function check($from_lines, $to_lines) {
+    if (serialize($from_lines) != serialize($this->orig())) {
+      trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
+    }
+    if (serialize($to_lines) != serialize($this->closing())) {
+      trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);
+    }
+
+    $rev = $this->reverse();
+    if (serialize($to_lines) != serialize($rev->orig())) {
+      trigger_error("Reversed original doesn't match", E_USER_ERROR);
+    }
+    if (serialize($from_lines) != serialize($rev->closing())) {
+      trigger_error("Reversed closing doesn't match", E_USER_ERROR);
+    }
+
+
+    $prevtype = 'none';
+    foreach ($this->edits as $edit) {
+      if ( $prevtype == $edit->type ) {
+        trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
+      }
+      $prevtype = $edit->type;
+    }
+
+    $lcs = $this->lcs();
+    trigger_error('Diff okay: LCS = ' . $lcs, E_USER_NOTICE);
+  }
+
+  /**
+   * Gets the list of differences as an array of diff operations.
+   *
+   * @return \Drupal\Component\Diff\Engine\DiffOp[]
+   *   The list of differences as an array of diff operations.
+   */
+  public function getEdits() {
+    return $this->edits;
+  }
+}
+

core/lib/Drupal/Component/Diff/DiffFormatter.php

+<?php
+
+namespace Drupal\Component\Diff;
+
+use Drupal\Component\Diff\Engine\DiffOpCopy;
+
+/**
+ * A class to format Diffs
+ *
+ * This class formats the diff in classic diff format.
+ * It is intended that this class be customized via inheritance,
+ * to obtain fancier outputs.
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffFormatter {
+  /**
+   * Should a block header be shown?
+   */
+  var $show_header = TRUE;
+
+  /**
+   * Number of leading context "lines" to preserve.
+   *
+   * This should be left at zero for this class, but subclasses
+   * may want to set this to other values.
+   */
+  var $leading_context_lines = 0;
+
+  /**
+   * Number of trailing context "lines" to preserve.
+   *
+   * This should be left at zero for this class, but subclasses
+   * may want to set this to other values.
+   */
+  var $trailing_context_lines = 0;
+
+  /**
+   * Format a diff.
+   *
+   * @param \Drupal\Component\Diff\Diff $diff
+   *   A Diff object.
+   *
+   * @return string
+   *   The formatted output.
+   */
+  public function format(Diff $diff) {
+    $xi = $yi = 1;
+    $block = FALSE;
+    $context = array();
+
+    $nlead = $this->leading_context_lines;
+    $ntrail = $this->trailing_context_lines;
+
+    $this->_start_diff();
+
+    foreach ($diff->getEdits() as $edit) {
+      if ($edit->type == 'copy') {
+        if (is_array($block)) {
+          if (sizeof($edit->orig) <= $nlead + $ntrail) {
+            $block[] = $edit;
+          }
+          else {
+            if ($ntrail) {
+              $context = array_slice($edit->orig, 0, $ntrail);
+              $block[] = new DiffOpCopy($context);
+            }
+            $this->_block($x0, $ntrail + $xi - $x0, $y0, $ntrail + $yi - $y0, $block);
+            $block = FALSE;
+          }
+        }
+        $context = $edit->orig;
+      }
+      else {
+        if (! is_array($block)) {
+          $context = array_slice($context, sizeof($context) - $nlead);
+          $x0 = $xi - sizeof($context);
+          $y0 = $yi - sizeof($context);
+          $block = array();
+          if ($context) {
+            $block[] = new DiffOpCopy($context);
+          }
+        }
+        $block[] = $edit;
+      }
+
+      if ($edit->orig) {
+        $xi += sizeof($edit->orig);
+      }
+      if ($edit->closing) {
+        $yi += sizeof($edit->closing);
+      }
+    }
+
+    if (is_array($block)) {
+      $this->_block($x0, $xi - $x0, $y0, $yi - $y0, $block);
+    }
+    $end = $this->_end_diff();
+
+    if (!empty($xi)) {
+      $this->line_stats['counter']['x'] += $xi;
+    }
+    if (!empty($yi)) {
+      $this->line_stats['counter']['y'] += $yi;
+    }
+
+    return $end;
+  }
+
+  protected function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
+    $this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
+    foreach ($edits as $edit) {
+      if ($edit->type == 'copy') {
+        $this->_context($edit->orig);
+      }
+      elseif ($edit->type == 'add') {
+        $this->_added($edit->closing);
+      }
+      elseif ($edit->type == 'delete') {
+        $this->_deleted($edit->orig);
+      }
+      elseif ($edit->type == 'change') {
+        $this->_changed($edit->orig, $edit->closing);
+      }
+      else {
+        trigger_error('Unknown edit type', E_USER_ERROR);
+      }
+    }
+    $this->_end_block();
+  }
+
+  protected function _start_diff() {
+    ob_start();
+  }
+
+  protected function _end_diff() {
+    $val = ob_get_contents();
+    ob_end_clean();
+    return $val;
+  }
+
+  protected function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+    if ($xlen > 1) {
+      $xbeg .= "," . ($xbeg + $xlen - 1);
+    }
+    if ($ylen > 1) {
+      $ybeg .= "," . ($ybeg + $ylen - 1);
+    }
+
+    return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
+  }
+
+  protected function _start_block($header) {
+    if ($this->show_header) {
+      echo $header . "\n";
+    }
+  }
+
+  protected function _end_block() {
+  }
+
+  protected function _lines($lines, $prefix = ' ') {
+    foreach ($lines as $line) {
+      echo "$prefix $line\n";
+    }
+  }
+
+  protected function _context($lines) {
+    $this->_lines($lines);
+  }
+
+  protected function _added($lines) {
+    $this->_lines($lines, '>');
+  }
+
+  protected function _deleted($lines) {
+    $this->_lines($lines, '<');
+  }
+
+  protected function _changed($orig, $closing) {
+    $this->_deleted($orig);
+    echo "---\n";
+    $this->_added($closing);
+  }
+
+}

core/lib/Drupal/Component/Diff/Engine/DiffOp.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffOp {
+  var $type;
+  var $orig;
+  var $closing;
+
+  public function reverse() {
+    trigger_error('pure virtual', E_USER_ERROR);
+  }
+
+  public function norig() {
+    return $this->orig ? sizeof($this->orig) : 0;
+  }
+
+  public function nclosing() {
+    return $this->closing ? sizeof($this->closing) : 0;
+  }
+}

core/lib/Drupal/Component/Diff/Engine/DiffOpAdd.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffOpAdd extends DiffOp {
+  var $type = 'add';
+
+  public function __construct($lines) {
+    $this->closing = $lines;
+    $this->orig = FALSE;
+  }
+
+  public function reverse() {
+    return new DiffOpDelete($this->closing);
+  }
+}

core/lib/Drupal/Component/Diff/Engine/DiffOpChange.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffOpChange extends DiffOp {
+  var $type = 'change';
+
+  public function __construct($orig, $closing) {
+    $this->orig = $orig;
+    $this->closing = $closing;
+  }
+
+  public function reverse() {
+    return new DiffOpChange($this->closing, $this->orig);
+  }
+}

core/lib/Drupal/Component/Diff/Engine/DiffOpCopy.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffOpCopy extends DiffOp {
+  var $type = 'copy';
+
+  public function __construct($orig, $closing = FALSE) {
+    if (!is_array($closing)) {
+      $closing = $orig;
+    }
+    $this->orig = $orig;
+    $this->closing = $closing;
+  }
+
+  public function reverse() {
+    return new DiffOpCopy($this->closing, $this->orig);
+  }
+}

core/lib/Drupal/Component/Diff/Engine/DiffOpDelete.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class DiffOpDelete extends DiffOp {
+  var $type = 'delete';
+
+  public function __construct($lines) {
+    $this->orig = $lines;
+    $this->closing = FALSE;
+  }
+
+  public function reverse() {
+    return new DiffOpAdd($this->orig);
+  }
+}

core/lib/Drupal/Component/Diff/Engine/HWLDFWordAccumulator.php

+<?php
+
+namespace Drupal\Component\Diff\Engine;
+
+use Drupal\Component\Utility\String;
+use Drupal\Component\Utility\Unicode;
+
+/**
+ *  Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
+ *
+ */
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class HWLDFWordAccumulator {
+
+  /**
+   * An iso-8859-x non-breaking space.
+   */
+  const NBSP = '&#160;';
+
+  protected $lines = array();
+
+  protected $line = '';
+
+  protected $group = '';
+
+  protected $tag = '';
+
+  protected function _flushGroup($new_tag) {
+    if ($this->group !== '') {
+      if ($this->tag == 'mark') {
+        $this->line .= '<span class="diffchange">' . String::checkPlain($this->group) . '</span>';
+      }
+      else {
+        $this->line .= String::checkPlain($this->group);
+      }
+    }
+    $this->group = '';
+    $this->tag = $new_tag;
+  }
+
+  protected function _flushLine($new_tag) {
+    $this->_flushGroup($new_tag);
+    if ($this->line != '') {
+      array_push($this->lines, $this->line);
+    }
+    else {
+      // make empty lines visible by inserting an NBSP
+      array_push($this->lines, $this::NBSP);
+    }
+    $this->line = '';
+  }
+
+  public function addWords($words, $tag = '') {
+    if ($tag != $this->tag) {
+      $this->_flushGroup($tag);
+    }
+    foreach ($words as $word) {
+      // new-line should only come as first char of word.
+      if ($word == '') {
+        continue;
+      }
+      if ($word[0] == "\n") {
+        $this->_flushLine($tag);
+        $word = Unicode::substr($word, 1);
+      }
+      assert(!strstr($word, "\n"));
+      $this->group .= $word;
+    }
+  }
+
+  public function getLines() {
+    $this->_flushLine('~done');
+    return $this->lines;
+  }
+}

core/lib/Drupal/Component/Diff/MappedDiff.php

+<?php
+
+namespace Drupal\Component\Diff;
+
+/**
+ * FIXME: bad name.
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class MappedDiff extends Diff {
+
+  /**
+   * Constructor.
+   *
+   * Computes diff between sequences of strings.
+   *
+   * This can be used to compute things like
+   * case-insensitive diffs, or diffs which ignore
+   * changes in white-space.
+   *
+   * @param $from_lines array An array of strings.
+   *  (Typically these are lines from a file.)
+   *
+   * @param $to_lines array An array of strings.
+   *
+   * @param $mapped_from_lines array This array should
+   *  have the same size number of elements as $from_lines.
+   *  The elements in $mapped_from_lines and
+   *  $mapped_to_lines are what is actually compared
+   *  when computing the diff.
+   *
+   * @param $mapped_to_lines array This array should
+   *  have the same number of elements as $to_lines.
+   */
+  public function __construct($from_lines, $to_lines, $mapped_from_lines, $mapped_to_lines) {
+
+    assert(sizeof($from_lines) == sizeof($mapped_from_lines));
+    assert(sizeof($to_lines) == sizeof($mapped_to_lines));
+
+    parent::__construct($mapped_from_lines, $mapped_to_lines);
+
+    $xi = $yi = 0;
+    for ($i = 0; $i < sizeof($this->edits); $i++) {
+      $orig = &$this->edits[$i]->orig;
+      if (is_array($orig)) {
+        $orig = array_slice($from_lines, $xi, sizeof($orig));
+        $xi += sizeof($orig);
+      }
+
+      $closing = &$this->edits[$i]->closing;
+      if (is_array($closing)) {
+        $closing = array_slice($to_lines, $yi, sizeof($closing));
+        $yi += sizeof($closing);
+      }
+    }
+  }
+}
+

core/lib/Drupal/Component/Diff/WordLevelDiff.php

+<?php
+
+namespace Drupal\Component\Diff;
+
+use Drupal\Component\Diff\Engine\HWLDFWordAccumulator;
+use Drupal\Component\Utility\Unicode;
+
+/**
+ * @todo document
+ * @private
+ * @subpackage DifferenceEngine
+ */
+class WordLevelDiff extends MappedDiff {
+
+  const MAX_LINE_LENGTH = 10000;
+
+  public function __construct($orig_lines, $closing_lines) {
+    list($orig_words, $orig_stripped) = $this->_split($orig_lines);
+    list($closing_words, $closing_stripped) = $this->_split($closing_lines);
+
+    parent::__construct($orig_words, $closing_words, $orig_stripped, $closing_stripped);
+  }
+
+  protected function _split($lines) {
+    $words = array();
+    $stripped = array();
+    $first = TRUE;
+    foreach ($lines as $line) {
+      // If the line is too long, just pretend the entire line is one big word
+      // This prevents resource exhaustion problems
+      if ( $first ) {
+        $first = FALSE;
+      }
+      else {
+        $words[] = "\n";
+        $stripped[] = "\n";
+      }
+      if (Unicode::strlen($line) > $this::MAX_LINE_LENGTH) {
+        $words[] = $line;
+        $stripped[] = $line;
+      }
+      else {
+        if (preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs', $line, $m)) {
+          $words = array_merge($words, $m[0]);
+          $stripped = array_merge($stripped, $m[1]);
+        }
+      }
+    }
+    return array($words, $stripped);
+  }
+
+  public function orig() {
+    $orig = new HWLDFWordAccumulator();
+
+    foreach ($this->edits as $edit) {
+      if ($edit->type == 'copy') {
+        $orig->addWords($edit->orig);
+      }
+      elseif ($edit->orig) {
+        $orig->addWords($edit->orig, 'mark');
+      }
+    }
+    $lines = $orig->getLines();
+    return $lines;
+  }
+
+  public function closing() {
+    $closing = new HWLDFWordAccumulator();
+
+    foreach ($this->edits as $edit) {
+      if ($edit->type == 'copy') {
+        $closing->addWords($edit->closing);
+      }
+      elseif ($edit->closing) {
+        $closing->addWords($edit->closing, 'mark');
+      }
+    }
+    $lines = $closing->getLines();
+    return $lines;
+  }
+}

core/lib/Drupal/Core/Config/ConfigManager.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Config;
 
+use Drupal\Component\Diff\Diff;
 use Drupal\Component\Serialization\Yaml;
 use Drupal\Core\Config\Entity\ConfigDependencyManager;
 use Drupal\Core\Entity\EntityManagerInterface;
@@ -130,10 +131,6 @@ public function diff(StorageInterface $source_storage, StorageInterface $target_
     if (!isset($target_name)) {
       $target_name = $source_name;
     }
-    // @todo Replace with code that can be autoloaded.
-    //   https://drupal.org/node/1848266
-    require_once __DIR__ . '/../../Component/Diff/DiffEngine.php';
-
     // The output should show configuration object differences formatted as YAML.
     // But the configuration is not necessarily stored in files. Therefore, they
     // need to be read and parsed, and lastly, dumped into YAML strings.
@@ -150,7 +147,7 @@ public function diff(StorageInterface $source_storage, StorageInterface $target_
       $target_data = array($this->t('File removed'));
     }
 
-    return new \Diff($source_data, $target_data);
+    return new Diff($source_data, $target_data);
   }
 
   /**

core/lib/Drupal/Core/Diff/DiffFormatter.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Diff\DiffFormatter.
+ */
+
+namespace Drupal\Core\Diff;
+
+use Drupal\Component\Diff\DiffFormatter as DiffFormatterBase;
+use Drupal\Component\Diff\WordLevelDiff;
+use Drupal\Component\Utility\String;
+use Drupal\Core\Config\ConfigFactoryInterface;
+
+/**
+ * Diff formatter which uses returns output that can be rendered to a table.
+ */
+class DiffFormatter extends DiffFormatterBase {
+
+  /**
+   * The diff represented as an array of rows.
+   *
+   * @var array
+   */
+  protected $rows = array();
+
+  /**
+   * The line stats.
+   *
+   * @var array
+   */
+  protected $line_stats = array(
+    'counter' => array('x' => 0, 'y' => 0),
+    'offset' => array('x' => 0, 'y' => 0),
+  );
+
+  /**
+   * Creates a DiffFormatter to render diffs in a table.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $config = $config_factory->get('system.diff');
+    $this->leading_context_lines = $config->get('context.lines_leading');
+    $this->trailing_context_lines = $config->get('context.lines_trailing');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _start_diff() {
+    $this->rows = array();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _end_diff() {
+    return $this->rows;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+    return array(
+      array(
+        'data' => $xbeg + $this->line_stats['offset']['x'],
+        'colspan' => 2,
+      ),
+      array(
+        'data' => $ybeg + $this->line_stats['offset']['y'],
+        'colspan' => 2,
+      )
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _start_block($header) {
+    if ($this->show_header) {
+      $this->rows[] = $header;
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _lines($lines, $prefix=' ', $color='white') {
+  }
+
+  /**
+   * Creates an added line.
+   *
+   * @param string $line
+   *   An HTML-escaped line.
+   *
+   * @return array
+   *   An array representing a table row.
+   */
+  protected function addedLine($line) {
+    return array(
+      array(
+        'data' => '+',
+        'class' => 'diff-marker',
+      ),
+      array(
+        'data' => $line,
+        'class' => 'diff-context diff-addedline',
+      )
+    );
+  }
+
+  /**
+   * Creates a deleted line.
+   *
+   * @param string $line
+   *   An HTML-escaped line.
+   *
+   * @return array
+   *   An array representing a table row.
+   */
+  protected function deletedLine($line) {
+    return array(
+      array(
+        'data' => '-',
+        'class' => 'diff-marker',
+      ),
+      array(
+        'data' => $line,
+        'class' => 'diff-context diff-deletedline',
+      )
+    );
+  }
+
+  /**
+   * Creates a context line.
+   *
+   * @param string $line
+   *   An HTML-escaped line.
+   *
+   * @return array
+   *   An array representing a table row.
+   */
+  protected function contextLine($line) {
+    return array(
+      '&nbsp;',
+      array(
+        'data' => $line,
+        'class' => 'diff-context',
+      )
+    );
+  }
+
+  /**
+   * Creates an empty line.
+   *
+   * @return array
+   *   An array representing a table row.
+   */
+  protected function emptyLine() {
+    return array(
+      '&nbsp;',
+      '&nbsp;',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _added($lines) {
+    foreach ($lines as $line) {
+      $this->rows[] = array_merge($this->emptyLine(), $this->addedLine(String::checkPlain($line)));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _deleted($lines) {
+    foreach ($lines as $line) {
+      $this->rows[] = array_merge($this->deletedLine(String::checkPlain($line)), $this->emptyLine());
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _context($lines) {
+    foreach ($lines as $line) {
+      $this->rows[] = array_merge($this->contextLine(String::checkPlain($line)), $this->contextLine(String::checkPlain($line)));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function _changed($orig, $closing) {
+    $diff = new WordLevelDiff($orig, $closing);
+    $del = $diff->orig();
+    $add = $diff->closing();
+
+    // Notice that WordLevelDiff returns HTML-escaped output. Hence, we will be
+    // calling addedLine/deletedLine without HTML-escaping.
+    while ($line = array_shift($del)) {
+      $aline = array_shift( $add );
+      $this->rows[] = array_merge($this->deletedLine($line), isset($aline) ? $this->addedLine($aline) : $this->emptyLine());
+    }
+
+    // If any leftovers.
+    foreach ($add as $line) {
+      $this->rows[] = array_merge($this->emptyLine(), $this->addedLine($line));
+    }
+  }
+}

core/modules/config/src/Controller/ConfigController.php

@@ -12,6 +12,7 @@
 use Drupal\Core\Config\ConfigManagerInterface;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\Diff\DiffFormatter;
 use Drupal\system\FileDownloadController;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
@@ -49,6 +50,13 @@ class ConfigController implements ContainerInjectionInterface {
    */
   protected $fileDownloadController;
 
+  /**
+   * The diff formatter.
+   *
+   * @var \Drupal\Core\Diff\DiffFormatter
+   */
+  protected $diffFormatter;
+
   /**
    * {@inheritdoc}
    */
@@ -57,7 +65,8 @@ public static function create(ContainerInterface $container) {
       $container->get('config.storage'),
       $container->get('config.storage.staging'),
       $container->get('config.manager'),
-      new FileDownloadController()
+      new FileDownloadController(),
+      $container->get('diff.formatter')
     );
   }
 
@@ -71,11 +80,12 @@ public static function create(ContainerInterface $container) {
    * @param \Drupal\system\FileDownloadController $file_download_controller
    *   The file download controller.
    */
-  public function __construct(StorageInterface $target_storage, StorageInterface $source_storage, ConfigManagerInterface $config_manager, FileDownloadController $file_download_controller) {
+  public function __construct(StorageInterface $target_storage, StorageInterface $source_storage, ConfigManagerInterface $config_manager, FileDownloadController $file_download_controller, DiffFormatter $diff_formatter) {
     $this->targetStorage = $target_storage;
     $this->sourceStorage = $source_storage;
     $this->configManager = $config_manager;
     $this->fileDownloadController = $file_download_controller;
+    $this->diffFormatter = $diff_formatter;
   }
 
   /**
@@ -102,7 +112,7 @@ public function downloadExport() {
   }
 
   /**
-   * Shows diff of specificed configuration file.
+   * Shows diff of specified configuration file.
    *
    * @param string $source_name
    *   The name of the configuration file.
@@ -121,8 +131,7 @@ public function diff($source_name, $target_name = NULL, $collection = NULL) {
       $collection = StorageInterface::DEFAULT_COLLECTION;
     }
     $diff = $this->configManager->diff($this->targetStorage, $this->sourceStorage, $source_name, $target_name, $collection);
-    $formatter = new \DrupalDiffFormatter();
-    $formatter->show_header = FALSE;
+    $this->diffFormatter->show_header = FALSE;
 
     $build = array();
 
@@ -136,7 +145,7 @@ public function diff($source_name, $target_name = NULL, $collection = NULL) {
         array('data' => t('Old'), 'colspan' => '2'),
         array('data' => t('New'), 'colspan' => '2'),
       ),
-      '#rows' => $formatter->format($diff),
+      '#rows' => $this->diffFormatter->format($diff),
     );
 
     $build['back'] = array(

core/modules/config/src/Tests/ConfigDiffTest.php

@@ -57,9 +57,10 @@ function testDiff() {
 
     // Verify that the diff reflects a change.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
-    $this->assertEqual($diff->edits[0]->type, 'change', 'The first item in the diff is a change.');
-    $this->assertEqual($diff->edits[0]->orig[0], $change_key . ': ' . $original_data[$change_key], format_string("The active value for key '%change_key' is '%original_data'.", array('%change_key' => $change_key, '%original_data' => $original_data[$change_key])));
-    $this->assertEqual($diff->edits[0]->closing[0], $change_key . ': ' . $change_data, format_string("The staging value for key '%change_key' is '%change_data'.", array('%change_key' => $change_key, '%change_data' => $change_data)));
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'change', 'The first item in the diff is a change.');
+    $this->assertEqual($edits[0]->orig[0], $change_key . ': ' . $original_data[$change_key], format_string("The active value for key '%change_key' is '%original_data'.", array('%change_key' => $change_key, '%original_data' => $original_data[$change_key])));
+    $this->assertEqual($edits[0]->closing[0], $change_key . ': ' . $change_data, format_string("The staging value for key '%change_key' is '%change_data'.", array('%change_key' => $change_key, '%change_data' => $change_data)));
 
     // Reset data back to original, and remove a key
     $staging_data = $original_data;
@@ -68,10 +69,11 @@ function testDiff() {
 
     // Verify that the diff reflects a removed key.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
-    $this->assertEqual($diff->edits[0]->type, 'copy', 'The first item in the diff is a copy.');
-    $this->assertEqual($diff->edits[1]->type, 'delete', 'The second item in the diff is a delete.');
-    $this->assertEqual($diff->edits[1]->orig[0], $remove_key . ': ' . $original_data[$remove_key], format_string("The active value for key '%remove_key' is '%original_data'.", array('%remove_key' => $remove_key, '%original_data' => $original_data[$remove_key])));
-    $this->assertFalse($diff->edits[1]->closing, format_string("The key '%remove_key' does not exist in staging.", array('%remove_key' => $remove_key)));
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'copy', 'The first item in the diff is a copy.');
+    $this->assertEqual($edits[1]->type, 'delete', 'The second item in the diff is a delete.');
+    $this->assertEqual($edits[1]->orig[0], $remove_key . ': ' . $original_data[$remove_key], format_string("The active value for key '%remove_key' is '%original_data'.", array('%remove_key' => $remove_key, '%original_data' => $original_data[$remove_key])));
+    $this->assertFalse($edits[1]->closing, format_string("The key '%remove_key' does not exist in staging.", array('%remove_key' => $remove_key)));
 
     // Reset data back to original and add a key
     $staging_data = $original_data;
@@ -80,10 +82,11 @@ function testDiff() {
 
     // Verify that the diff reflects an added key.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
-    $this->assertEqual($diff->edits[0]->type, 'copy', 'The first item in the diff is a copy.');
-    $this->assertEqual($diff->edits[1]->type, 'add', 'The second item in the diff is an add.');
-    $this->assertFalse($diff->edits[1]->orig, format_string("The key '%add_key' does not exist in active.", array('%add_key' => $add_key)));
-    $this->assertEqual($diff->edits[1]->closing[0], $add_key . ': ' . $add_data, format_string("The staging value for key '%add_key' is '%add_data'.", array('%add_key' => $add_key, '%add_data' => $add_data)));
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'copy', 'The first item in the diff is a copy.');
+    $this->assertEqual($edits[1]->type, 'add', 'The second item in the diff is an add.');
+    $this->assertFalse($edits[1]->orig, format_string("The key '%add_key' does not exist in active.", array('%add_key' => $add_key)));
+    $this->assertEqual($edits[1]->closing[0], $add_key . ': ' . $add_data, format_string("The staging value for key '%add_key' is '%add_data'.", array('%add_key' => $add_key, '%add_data' => $add_data)));
 
     // Test diffing a renamed config entity.
     $test_entity_id = $this->randomName();
@@ -97,8 +100,9 @@ function testDiff() {
     $config_name = 'config_test.dynamic.' . $test_entity_id;
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name, $config_name);
     // Prove the fields match.
-    $this->assertEqual($diff->edits[0]->type, 'copy',  'The first item in the diff is a copy.');
-    $this->assertEqual(count($diff->edits), 1, 'There is one item in the diff');
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'copy',  'The first item in the diff is a copy.');
+    $this->assertEqual(count($edits), 1, 'There is one item in the diff');
 
     // Rename the entity.
     $new_test_entity_id = $this->randomName();
@@ -106,11 +110,12 @@ function testDiff() {
     $test_entity->save();
 
     $diff = \Drupal::service('config.manager')->diff($active, $staging, 'config_test.dynamic.' . $new_test_entity_id, $config_name);
-    $this->assertEqual($diff->edits[0]->type, 'change',  'The second item in the diff is a copy.');
-    $this->assertEqual($diff->edits[0]->orig, array('id: ' . $new_test_entity_id));
-    $this->assertEqual($diff->edits[0]->closing, array('id: ' . $test_entity_id));
-    $this->assertEqual($diff->edits[1]->type, 'copy',  'The second item in the diff is a copy.');
-    $this->assertEqual(count($diff->edits), 2, 'There are two items in the diff.');
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'change',  'The second item in the diff is a copy.');
+    $this->assertEqual($edits[0]->orig, array('id: ' . $new_test_entity_id));
+    $this->assertEqual($edits[0]->closing, array('id: ' . $test_entity_id));
+    $this->assertEqual($edits[1]->type, 'copy',  'The second item in the diff is a copy.');
+    $this->assertEqual(count($edits), 2, 'There are two items in the diff.');
   }
 
   /**
@@ -134,15 +139,17 @@ function testCollectionDiff() {
 
     // Test the fields match in the default collection diff.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
-    $this->assertEqual($diff->edits[0]->type, 'copy',  'The first item in the diff is a copy.');
-    $this->assertEqual(count($diff->edits), 1, 'There is one item in the diff');
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'copy',  'The first item in the diff is a copy.');
+    $this->assertEqual(count($edits), 1, 'There is one item in the diff');
 
     // Test that the differences are detected when diffing the collection.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name, NULL, 'test');
-    $this->assertEqual($diff->edits[0]->type, 'change',  'The second item in the diff is a copy.');
-    $this->assertEqual($diff->edits[0]->orig, array('foo: bar'));
-    $this->assertEqual($diff->edits[0]->closing, array('foo: baz'));
-    $this->assertEqual($diff->edits[1]->type, 'copy',  'The second item in the diff is a copy.');
+    $edits = $diff->getEdits();
+    $this->assertEqual($edits[0]->type, 'change',  'The second item in the diff is a copy.');
+    $this->assertEqual($edits[0]->orig, array('foo: bar'));
+    $this->assertEqual($edits[0]->closing, array('foo: baz'));
+    $this->assertEqual($edits[1]->type, 'copy',  'The second item in the diff is a copy.');
   }
 
 }

core/modules/system/config/install/system.diff.yml

+context:
+  lines_leading: 2
+  lines_trailing: 2

core/modules/system/config/schema/system.schema.yml

@@ -128,6 +128,21 @@ system.date_format.*:
       type: string
       label: 'Default language'
 
+system.diff:
+  type: mapping
+  label: 'Diff settings'
+  mapping:
+    context:
+      type: mapping
+      label: 'Context'
+      mapping:
+        lines_leading:
+          type: integer
+          label: 'Number of leading lines in a diff'
+        lines_trailing:
+          type: integer
+          label: 'Number of trailing lines in a diff'
+
 system.filter:
   type: mapping
   label: 'Filter settings'