Add three new sniffs for LearnDash coding standards

src/LearnDash/Sniffs/Classes/DisallowNonPrivateConstSniff.php

@@ -0,0 +1,105 @@
+<?php
+/**
+ * Disallows public and protected class constants.
+ *
+ * Public/protected class constants cannot be deprecated, so we should use
+ * public/protected static properties instead.
+ *
+ * @package StellarWP/learndash-php-sniffs
+ */
+
+namespace StellarWP\PHP_Sniffs\LearnDash\Sniffs\Classes;
+
+use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\Sniff;
+
+/**
+ * DisallowNonPrivateConstSniff class
+ */
+class DisallowNonPrivateConstSniff implements Sniff {
+	/**
+	 * Returns an array of tokens this test wants to listen for.
+	 *
+	 * @return array<int>
+	 */
+	public function register(): array {
+		return [ T_CONST ];
+	}
+
+	/**
+	 * Processes this test, when one of its tokens is encountered.
+	 *
+	 * @param File $phpcs_file The file being scanned.
+	 * @param int  $stack_ptr  The position of the current token in the stack.
+	 *
+	 * @return void
+	 *
+	 * @phpcs:disable SlevomatCodingStandard.TypeHints.ParameterTypeHint.MissingNativeTypeHint
+	 */
+	public function process( File $phpcs_file, $stack_ptr ): void {
+		$tokens = $phpcs_file->getTokens();
+
+		// Check if this const is inside a class/interface/trait.
+		if ( empty( $tokens[ $stack_ptr ]['conditions'] ) ) {
+			return;
+		}
+
+		$conditions     = $tokens[ $stack_ptr ]['conditions'];
+		$last_condition = end( $conditions );
+		$valid_scopes   = [ T_CLASS, T_INTERFACE, T_TRAIT, T_ENUM ];
+
+		if ( ! in_array( $last_condition, $valid_scopes, true ) ) {
+			return;
+		}
+
+		// Skip over whitespace, comments, and 'final' keyword to find visibility modifier.
+		$skip_tokens = [
+			T_WHITESPACE,
+			T_FINAL,
+			T_COMMENT,
+			T_DOC_COMMENT_CLOSE_TAG,
+		];
+
+		$previous_ptr = $phpcs_file->findPrevious(
+			$skip_tokens,
+			$stack_ptr - 1,
+			null,
+			true, // Exclude these tokens (find something that's NOT in this list).
+			null,
+			true  // Local scope only.
+		);
+
+		if ( $previous_ptr === false ) {
+			// No visibility means public by default in PHP.
+			$phpcs_file->addError(
+				'Class constants should be private. Use a static property for public/protected visibility to allow deprecation.',
+				$stack_ptr,
+				'ImplicitPublicConst'
+			);
+			return;
+		}
+
+		$previous_token = $tokens[ $previous_ptr ];
+
+		if ( $previous_token['code'] === T_PUBLIC ) {
+			$phpcs_file->addError(
+				'Public class constants are not allowed. Use a public static property instead to allow deprecation.',
+				$stack_ptr,
+				'PublicConst'
+			);
+		} elseif ( $previous_token['code'] === T_PROTECTED ) {
+			$phpcs_file->addError(
+				'Protected class constants are not allowed. Use a protected static property instead to allow deprecation.',
+				$stack_ptr,
+				'ProtectedConst'
+			);
+		} elseif ( $previous_token['code'] !== T_PRIVATE ) {
+			// No visibility modifier found (implicit public).
+			$phpcs_file->addError(
+				'Class constants should be private. Use a static property for public/protected visibility to allow deprecation.',
+				$stack_ptr,
+				'ImplicitPublicConst'
+			);
+		}
+	}
+}