Add / display Custom meta field on WooCommerce General Product Tab

woocomerce-hack.php

<?php

	add_action('woocommerce_product_options_general_product_data', 'addCustomMetaDataProductGeneralTab' );
    function addCustomMetaDataProductGeneralTab() { 
        woocommerce_wp_text_input( 
			[
				'id' => '__optimist_color',
				'label' => 'Product Color',
				'description' => 'Add product color', 
			]
		);
        woocommerce_wp_text_input( 
			[
				'id' => '__optimist_stone_details',
				'label' => 'Stone Details',
				'description' => 'Add stone details', 
			]
		);
        woocommerce_wp_text_input( 
			[
				'id' => '__optimist_main_details',
				'label' => 'Main Details',
				'description' => 'Add main details', 
			]
		);
    }

    add_action( 'woocommerce_process_product_meta', 'saveCustomMetaDataProductGeneralTab' );
    function saveCustomMetaDataProductGeneralTab( $post_id ) 
	{
        if ( ! empty( $_POST['__optimist_color'] ) ) {
            update_post_meta( $post_id, '__optimist_color', esc_attr( $_POST['__optimist_color'] ) );
        }
        if ( ! empty( $_POST['__optimist_stone_details'] ) ) {
            update_post_meta( $post_id, '__optimist_stone_details', esc_attr( $_POST['__optimist_stone_details'] ) );
        }
        if ( ! empty( $_POST['__optimist_main_details'] ) ) {
            update_post_meta( $post_id, '__optimist_main_details', esc_attr( $_POST['__optimist_main_details'] ) );
        }
    }

	add_action('woocommerce_product_meta_end','displayCustoProductMetaOnFrontEnd' );
	function displayCustoProductMetaOnFrontEnd() 
	{
		global $post;

		$postId 	= $post->ID;
		$__color 	= get_post_meta( $postId, '__optimist_color' ,true);
		$__stone 	= get_post_meta( $postId, '__optimist_stone_details' ,true);
		$__main 	= get_post_meta( $postId, '__optimist_main_details' ,true);

		if(strlen($__color))
		{
			echo '<span class="tagged_as"><span class="qodef-woo-meta-label">Color:</span><span class="qodef-woo-meta-value">'.$__color.'</span></span>';
		}
		if(strlen($__stone))
		{
			echo '<span class="tagged_as"><span class="qodef-woo-meta-label">Stone Details:</span><span class="qodef-woo-meta-value">'.$__stone.'</span></span>';
		}
		if(strlen($__main))
		{
			echo '<span class="tagged_as"><span class="qodef-woo-meta-label">Main Details:</span><span class="qodef-woo-meta-value">'.$__main.'</span></span>';
		}
	}