Generators: add tests covering handling of invalid docs

This adds another set of dedicated tests to safeguard how XML docs which don't follow the specification are handled.

This initial set of tests for this documents the current behaviour [*]. This behaviour may not always be the desired behaviour, in which case, this will be fixed in follow-up commits.

To get these tests up and running, the following fatal errors needed to be fixed:

* Fatal error when a code comparison only contains a single code element:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:253
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 253
    ```

* Fatal error when a code element contains no textual content:
    ```
    Fatal error: Uncaught Error: Call to a member function getAttribute() on null in path/to/PHP_CodeSniffer/src/Generators/Markdown.php:246
    Stack trace:
    #0 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(139): PHP_CodeSniffer\Generators\Markdown->getFormattedCodeComparisonBlock(Object(DOMElement))
    #1 path/to/PHP_CodeSniffer/src/Generators/Markdown.php(39): PHP_CodeSniffer\Generators\Markdown->processSniff(Object(DOMElement))
    squizlabs#2 path/to/PHP_CodeSniffer/src/Runner.php(99): PHP_CodeSniffer\Generators\Markdown->generate()
    squizlabs#3 path/to/PHP_CodeSniffer/bin/phpcs(14): PHP_CodeSniffer\Runner->runPHPCS()
    squizlabs#4 {main}
      thrown in path/to/PHP_CodeSniffer/src/Generators/Markdown.php on line 246
    ```

Both of these fatals are fixed by adding defensive coding validating that there are (at least) two code blocks to the `getFormattedCodeComparisonBlock()` methods for all three generator classes.

src/Generators/HTML.php

@@ -383,20 +383,27 @@ protected function printCodeComparisonBlock(DOMNode $node)
      */
     protected function getFormattedCodeComparisonBlock(DOMNode $node)
     {
-        $codeBlocks = $node->getElementsByTagName('code');
+        $codeBlocks    = $node->getElementsByTagName('code');
+        $firstCodeElm  = $codeBlocks->item(0);
+        $secondCodeElm = $codeBlocks->item(1);
 
-        $firstTitle = trim($codeBlocks->item(0)->getAttribute('title'));
+        if (isset($firstCodeElm, $secondCodeElm) === false) {
+            // Missing at least one code block.
+            return '';
+        }
+
+        $firstTitle = trim($firstCodeElm->getAttribute('title'));
         $firstTitle = str_replace('  ', '  ', $firstTitle);
-        $first      = trim($codeBlocks->item(0)->nodeValue);
+        $first      = trim($firstCodeElm->nodeValue);
         $first      = str_replace('<?php', '&lt;?php', $first);
         $first      = str_replace("\n", '</br>', $first);
         $first      = str_replace(' ', '&nbsp;', $first);
         $first      = str_replace('<em>', '<span class="code-comparison-highlight">', $first);
         $first      = str_replace('</em>', '</span>', $first);
 
-        $secondTitle = trim($codeBlocks->item(1)->getAttribute('title'));
+        $secondTitle = trim($secondCodeElm->getAttribute('title'));
         $secondTitle = str_replace('  ', '&nbsp;&nbsp;', $secondTitle);
-        $second      = trim($codeBlocks->item(1)->nodeValue);
+        $second      = trim($secondCodeElm->nodeValue);
         $second      = str_replace('<?php', '&lt;?php', $second);
         $second      = str_replace("\n", '</br>', $second);
         $second      = str_replace(' ', '&nbsp;', $second);

src/Generators/Markdown.php

@@ -241,18 +241,25 @@ protected function printCodeComparisonBlock(DOMNode $node)
      */
     protected function getFormattedCodeComparisonBlock(DOMNode $node)
     {
-        $codeBlocks = $node->getElementsByTagName('code');
+        $codeBlocks    = $node->getElementsByTagName('code');
+        $firstCodeElm  = $codeBlocks->item(0);
+        $secondCodeElm = $codeBlocks->item(1);
 
-        $firstTitle = trim($codeBlocks->item(0)->getAttribute('title'));
+        if (isset($firstCodeElm, $secondCodeElm) === false) {
+            // Missing at least one code block.
+            return '';
+        }
+
+        $firstTitle = trim($firstCodeElm->getAttribute('title'));
         $firstTitle = str_replace('  ', '  ', $firstTitle);
-        $first      = trim($codeBlocks->item(0)->nodeValue);
+        $first      = trim($firstCodeElm->nodeValue);
         $first      = str_replace("\n", PHP_EOL.'    ', $first);
         $first      = str_replace('<em>', '', $first);
         $first      = str_replace('</em>', '', $first);
 
-        $secondTitle = trim($codeBlocks->item(1)->getAttribute('title'));
+        $secondTitle = trim($secondCodeElm->getAttribute('title'));
         $secondTitle = str_replace('  ', '&nbsp;&nbsp;', $secondTitle);
-        $second      = trim($codeBlocks->item(1)->nodeValue);
+        $second      = trim($secondCodeElm->nodeValue);
         $second      = str_replace("\n", PHP_EOL.'    ', $second);
         $second      = str_replace('<em>', '', $second);
         $second      = str_replace('</em>', '', $second);

src/Generators/Text.php

@@ -198,9 +198,17 @@ protected function printCodeComparisonBlock(DOMNode $node)
      */
     protected function getFormattedCodeComparisonBlock(DOMNode $node)
     {
-        $codeBlocks = $node->getElementsByTagName('code');
-        $first      = trim($codeBlocks->item(0)->nodeValue);
-        $firstTitle = trim($codeBlocks->item(0)->getAttribute('title'));
+        $codeBlocks    = $node->getElementsByTagName('code');
+        $firstCodeElm  = $codeBlocks->item(0);
+        $secondCodeElm = $codeBlocks->item(1);
+
+        if (isset($firstCodeElm, $secondCodeElm) === false) {
+            // Missing at least one code block.
+            return '';
+        }
+
+        $first      = trim($firstCodeElm->nodeValue);
+        $firstTitle = trim($firstCodeElm->getAttribute('title'));
 
         $firstTitleLines = [];
         $tempTitle       = '';
@@ -234,8 +242,8 @@ protected function getFormattedCodeComparisonBlock(DOMNode $node)
         $first      = str_replace('</em>', '', $first);
         $firstLines = explode("\n", $first);
 
-        $second      = trim($codeBlocks->item(1)->nodeValue);
-        $secondTitle = trim($codeBlocks->item(1)->getAttribute('title'));
+        $second      = trim($secondCodeElm->nodeValue);
+        $secondTitle = trim($secondCodeElm->getAttribute('title'));
 
         $secondTitleLines = [];
         $tempTitle        = '';

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMismatchedCodeElms.html

@@ -0,0 +1,88 @@
+<html>
+ <head>
+  <title>GeneratorTest Coding Standards</title>
+  <style>
+        body {
+            background-color: #FFFFFF;
+            font-size: 14px;
+            font-family: Arial, Helvetica, sans-serif;
+            color: #000000;
+        }
+
+        h1 {
+            color: #666666;
+            font-size: 20px;
+            font-weight: bold;
+            margin-top: 0px;
+            background-color: #E6E7E8;
+            padding: 20px;
+            border: 1px solid #BBBBBB;
+        }
+
+        h2 {
+            color: #00A5E3;
+            font-size: 16px;
+            font-weight: normal;
+            margin-top: 50px;
+        }
+
+        .code-comparison {
+            width: 100%;
+        }
+
+        .code-comparison td {
+            border: 1px solid #CCCCCC;
+        }
+
+        .code-comparison-title, .code-comparison-code {
+            font-family: Arial, Helvetica, sans-serif;
+            font-size: 12px;
+            color: #000000;
+            vertical-align: top;
+            padding: 4px;
+            width: 50%;
+            background-color: #F1F1F1;
+            line-height: 15px;
+        }
+
+        .code-comparison-code {
+            font-family: Courier;
+            background-color: #F9F9F9;
+        }
+
+        .code-comparison-highlight {
+            background-color: #DDF1F7;
+            border: 1px solid #00A5E3;
+            line-height: 15px;
+        }
+
+        .tag-line {
+            text-align: center;
+            width: 100%;
+            margin-top: 30px;
+            font-size: 12px;
+        }
+
+        .tag-line a {
+            color: #000000;
+        }
+    </style>
+ </head>
+ <body>
+  <h1>GeneratorTest Coding Standards</h1>
+  <a name="Code-Comparison,-mismatched-code-blocks" />
+  <h2>Code Comparison, mismatched code blocks</h2>
+  <p class="text">This doc has two code elements, one only has a title, one has actual code. Unbalanced</p>
+  <table class="code-comparison">
+   <tr>
+    <td class="code-comparison-title">Code title</td>
+    <td class="code-comparison-title"></td>
+   </tr>
+   <tr>
+    <td class="code-comparison-code"></td>
+    <td class="code-comparison-code">$a&nbsp;=&nbsp;'Example&nbsp;code';</td>
+   </tr>
+  </table>
+  <div class="tag-line">Documentation generated on #REDACTED# by <a href="https://github.com/PHPCSStandards/PHP_CodeSniffer">PHP_CodeSniffer #VERSION#</a></div>
+ </body>
+</html>

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMismatchedCodeElms.md

@@ -0,0 +1,25 @@
+# GeneratorTest Coding Standard
+
+## Code Comparison, mismatched code blocks
+
+This doc has two code elements, one only has a title, one has actual code. Unbalanced
+  <table>
+   <tr>
+    <th>Code title</th>
+    <th></th>
+   </tr>
+   <tr>
+<td>
+
+
+
+</td>
+<td>
+
+    $a = 'Example code';
+
+</td>
+   </tr>
+  </table>
+
+Documentation generated on *REDACTED* by [PHP_CodeSniffer *VERSION*](https://github.com/PHPCSStandards/PHP_CodeSniffer)

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMismatchedCodeElms.txt

@@ -0,0 +1,13 @@
+
+--------------------------------------------------------------------------
+| GENERATORTEST CODING STANDARD: CODE COMPARISON, MISMATCHED CODE BLOCKS |
+--------------------------------------------------------------------------
+
+This doc has two code elements, one only has a title, one has actual code. Unbalanced
+
+----------------------------------------- CODE COMPARISON ------------------------------------------
+| Code title                                     |                                                 |
+----------------------------------------------------------------------------------------------------
+|                                                | $a = 'Example code';                            |
+----------------------------------------------------------------------------------------------------
+

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMissingCodeElm.html

@@ -0,0 +1,78 @@
+<html>
+ <head>
+  <title>GeneratorTest Coding Standards</title>
+  <style>
+        body {
+            background-color: #FFFFFF;
+            font-size: 14px;
+            font-family: Arial, Helvetica, sans-serif;
+            color: #000000;
+        }
+
+        h1 {
+            color: #666666;
+            font-size: 20px;
+            font-weight: bold;
+            margin-top: 0px;
+            background-color: #E6E7E8;
+            padding: 20px;
+            border: 1px solid #BBBBBB;
+        }
+
+        h2 {
+            color: #00A5E3;
+            font-size: 16px;
+            font-weight: normal;
+            margin-top: 50px;
+        }
+
+        .code-comparison {
+            width: 100%;
+        }
+
+        .code-comparison td {
+            border: 1px solid #CCCCCC;
+        }
+
+        .code-comparison-title, .code-comparison-code {
+            font-family: Arial, Helvetica, sans-serif;
+            font-size: 12px;
+            color: #000000;
+            vertical-align: top;
+            padding: 4px;
+            width: 50%;
+            background-color: #F1F1F1;
+            line-height: 15px;
+        }
+
+        .code-comparison-code {
+            font-family: Courier;
+            background-color: #F9F9F9;
+        }
+
+        .code-comparison-highlight {
+            background-color: #DDF1F7;
+            border: 1px solid #00A5E3;
+            line-height: 15px;
+        }
+
+        .tag-line {
+            text-align: center;
+            width: 100%;
+            margin-top: 30px;
+            font-size: 12px;
+        }
+
+        .tag-line a {
+            color: #000000;
+        }
+    </style>
+ </head>
+ <body>
+  <h1>GeneratorTest Coding Standards</h1>
+  <a name="Code-Comparison,-missing-code-element" />
+  <h2>Code Comparison, missing code element</h2>
+  <p class="text">This is a standard block.</p>
+  <div class="tag-line">Documentation generated on #REDACTED# by <a href="https://github.com/PHPCSStandards/PHP_CodeSniffer">PHP_CodeSniffer #VERSION#</a></div>
+ </body>
+</html>

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMissingCodeElm.md

@@ -0,0 +1,7 @@
+# GeneratorTest Coding Standard
+
+## Code Comparison, missing code element
+
+This is a standard block.
+
+Documentation generated on *REDACTED* by [PHP_CodeSniffer *VERSION*](https://github.com/PHPCSStandards/PHP_CodeSniffer)

tests/Core/Generators/Expectations/ExpectedOutputInvalidCodeComparisonMissingCodeElm.txt

@@ -0,0 +1,7 @@
+
+------------------------------------------------------------------------
+| GENERATORTEST CODING STANDARD: CODE COMPARISON, MISSING CODE ELEMENT |
+------------------------------------------------------------------------
+
+This is a standard block.
+