When creating terms, avoid false dupe checks due to accented characters.

`wp_insert_term()` doesn't allow the creation of a term when the term `name`
is the same as another term in the same hierarchy level of the same taxonomy.
Previously, this duplicate check used `get_term_by( 'name' )`, which uses the
database collation to determine sameness. But common collations do not
distinguish between accented and non-accented versions of a character. As a
result, it was impossible to create a term 'Foo' if a sibling term with an
accented character existed.

We address this problem by using `get_terms()` to do the duplicate check. This
query returns all potentially matching terms. We then do a stricter check
for equivalence in PHP, before determining whether one of the matches is
indeed a duplicate.

Props boonebgorges, tyxla, geza.miklo, mehulkaklotar.
Fixes #33864.

git-svn-id: https://develop.svn.wordpress.org/trunk@34809 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/taxonomy-functions.php

@@ -2516,7 +2516,26 @@ function wp_insert_term( $term, $taxonomy, $args = array() ) {
 	 * Prevent the creation of terms with duplicate names at the same level of a taxonomy hierarchy,
 	 * unless a unique slug has been explicitly provided.
 	 */
-	if ( $name_match = get_term_by( 'name', $name, $taxonomy ) ) {
+	$name_matches = get_terms( $taxonomy, array(
+		'name' => $name,
+		'hide_empty' => false,
+	) );
+
+	/*
+	 * The `name` match in `get_terms()` doesn't differentiate accented characters,
+	 * so we do a stricter comparison here.
+	 */
+	$name_match = null;
+	if ( $name_matches ) {
+		foreach ( $name_matches as $_match ) {
+			if ( strtolower( $name ) === strtolower( $_match->name ) ) {
+				$name_match = $_match;
+				break;
+			}
+		}
+	}
+
+	if ( $name_match ) {
 		$slug_match = get_term_by( 'slug', $slug, $taxonomy );
 		if ( ! $slug_provided || $name_match->slug === $slug || $slug_match ) {
 			if ( is_taxonomy_hierarchical( $taxonomy ) ) {

tests/phpunit/tests/term/wpInsertTerm.php

@@ -628,6 +628,31 @@ class Tests_Term_WpInsertTerm extends WP_UnitTestCase {
 		$this->assertTrue( in_array( $found['term_id'], $cached_children[ $t ] ) );
 	}
 
+	/**
+	 * @ticket 33864
+	 */
+	public function test_wp_insert_term_with_and_without_accents() {
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		$t1 = $this->factory->term->create( array(
+			'name' => 'Foó',
+			'taxonomy' => 'wptests_tax',
+		) );
+		$t2 = $this->factory->term->create( array(
+			'name' => 'Foo',
+			'taxonomy' => 'wptests_tax',
+		) );
+
+		$this->assertInternalType( 'int', $t1 );
+		$this->assertInternalType( 'int', $t2 );
+		$this->assertNotEquals( $t1, $t2 );
+
+		$term_2 = get_term( $t2, 'wptests_tax' );
+		$this->assertSame( $t2, $term_2->term_id );
+		$this->assertSame( 'Foo', $term_2->name );
+
+	}
+
 	/** Helpers **********************************************************/
 
 	public function deleted_term_cb( $term, $tt_id, $taxonomy, $deleted_term ) {