Formatting: Treat math elements as block-level elements.

The `math` element can be displayed either as a block or inline element. If `wpautop` only treats it as an inline element, it will break multiline elements by inserting `br` elements. Treating the element as a block element means that the editor won't break common normative usages of the `math` element. 

Prevent `math` elements from having internal elements split up with `br` elements, disrupting formatting.

Props nicholaswilson, wojtek.szkutnik, hakre, conner_bw, ericlewis, hughie.molloy, SteelWagstaff, ryokuhi, joedolson, bgoewert, adamsilverstein, joedolson.
Fixes #13340.

git-svn-id: https://develop.svn.wordpress.org/trunk@55272 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-includes/formatting.php

@@ -480,7 +480,7 @@ function wpautop( $text, $br = true ) {
 	// Change multiple <br>'s into two line breaks, which will turn into paragraphs.
 	$text = preg_replace( '|<br\s*/?>\s*<br\s*/?>|', "\n\n", $text );
 
-	$allblocks = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|form|map|area|blockquote|address|math|style|p|h[1-6]|hr|fieldset|legend|section|article|aside|hgroup|header|footer|nav|figure|figcaption|details|menu|summary)';
+	$allblocks = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|form|map|area|blockquote|address|style|p|h[1-6]|hr|fieldset|legend|section|article|aside|hgroup|header|footer|nav|figure|figcaption|details|menu|summary)';
 
 	// Add a double line break above block-level opening tags.
 	$text = preg_replace( '!(<' . $allblocks . '[\s/>])!', "\n\n$1", $text );
@@ -568,7 +568,7 @@ function wpautop( $text, $br = true ) {
 	// Optionally insert line breaks.
 	if ( $br ) {
 		// Replace newlines that shouldn't be touched with a placeholder.
-		$text = preg_replace_callback( '/<(script|style|svg).*?<\/\\1>/s', '_autop_newline_preservation_helper', $text );
+		$text = preg_replace_callback( '/<(script|style|svg|math).*?<\/\\1>/s', '_autop_newline_preservation_helper', $text );
 
 		// Normalize <br>
 		$text = str_replace( array( '<br>', '<br/>' ), '<br />', $text );

tests/phpunit/tests/formatting/wpAutop.php

@@ -104,6 +104,63 @@ public function test_skip_input_elements() {
 		$this->assertSame( "<p>$str</p>", trim( wpautop( $str ) ) );
 	}
 
+	/**
+	 * wpautop() Should add <p> around inline "<math>" elements.
+	 *
+	 * @ticket 13340
+	 */
+	public function test_wrap_inline_math_elements() {
+		$str = '<math><mrow><msup><mi>a</mi><mn>2</mn></msup><mo>+</mo><msup><mi>b</mi><mn>2</mn></msup><mo>=</mo><msup><mi>c</mi><mn>2</mn></msup></mrow></math>';
+
+		$this->assertSame( "<p>$str</p>", trim( wpautop( $str ) ) );
+	}
+
+	/**
+	 * wpautop() Should not add <br> inside block "<math>" elements.
+	 *
+	 * @ticket 13340
+	 */
+	public function test_skip_block_math_elements() {
+		$str = '<math display="block">
+	<mtable>
+		<mtr>
+			<mtd>
+				<msup><mrow><mo>(</mo><mi>a</mi><mo>+</mo><mi>b</mi><mo>)</mo></mrow><mn>2</mn></msup>
+			</mtd>
+			<mtd>
+				<mo>=</mo>
+			</mtd>
+			<mtd>
+				<msup><mi>c</mi><mn>2</mn></msup>
+				<mo>+</mo><mn>4</mn><mo>⋅</mo>
+				<mo>(</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>a</mi><mi>b</mi><mo>)</mo>
+			</mtd>
+		</mtr>
+		<mtr>
+			<mtd>
+				<msup><mi>a</mi><mn>2</mn></msup>
+				<mo>+</mo><mn>2</mn><mi>a</mi><mi>b</mi><mo>+</mo>
+				<msup><mi>b</mi><mn>2</mn></msup>
+			</mtd>
+			<mtd>
+				<mo>=</mo>
+			</mtd>
+			<mtd>
+				<msup><mi>c</mi><mn>2</mn></msup>
+				<mo>+</mo><mn>2</mn><mi>a</mi><mi>b</mi>
+			</mtd>
+		</mtr>
+		<mtr>
+			<mtd><msup><mi>a</mi><mn>2</mn></msup><mo>+</mo><msup><mi>b</mi><mn>2</mn></msup></mtd>
+			<mtd><mo>=</mo></mtd>
+			<mtd><msup><mi>c</mi><mn>2</mn></msup></mtd>
+		</mtr>
+	</mtable>
+</math>';
+
+		$this->assertSame( "<p>$str</p>", trim( wpautop( $str ) ) );
+	}
+
 	/**
 	 * wpautop() Should not add <p> and <br/> around <source> and <track>
 	 *
@@ -308,7 +365,6 @@ public function test_that_wpautop_treats_block_level_elements_as_blocks() {
 			'map',
 			'area',
 			'address',
-			'math',
 			'style',
 			'p',
 			'h1',