add-inline-scripts.php

<?php
/**
 * Plugin Name: Add Inline Scripts (and Styles)
 * Description: Test case to debug AMP plugin source attribution problems.
 * Author: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * Plugin URI: https://amp-wp.org
 * License: GPLv2 or later
 */

namespace Add_Inline_Scripts;

/**
 * Add inline style.
 */
function enqueue_assets() {
	wp_enqueue_script( 'underscore' );
	wp_localize_script( 'underscore', 'Hello_Underscores', [ 'message' => 'Hello wp_localize_script()!' ] );
	wp_add_inline_script( 'underscore', '/*Hello wp_add_inline_script( before )!*/', 'before' );
	wp_add_inline_script( 'underscore', '/*Hello wp_add_inline_script( after )!*/', 'after' );

	wp_add_inline_style( get_template() . '-style', '#add-inline-scripts-styled { color: blue; }' );
}
add_action( 'wp_enqueue_scripts', __NAMESPACE__ . '\enqueue_assets', 11 );

add_action(
	'wp_footer',
	function () {
		echo '<div id="add-inline-scripts-styled">Styled by add-inline-scripts</div>';
	}
);

add-more-inline-scripts.php

<?php
/**
 * Plugin Name: Add More Inline Scripts
 * Description: Test case to debug AMP plugin source attribution problems.
 * Author: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * Plugin URI: https://amp-wp.org
 * License: GPLv2 or later
 */

namespace Add_More_Inline_Scripts;

/**
 * Add inline style.
 */
function enqueue_assets() {
	wp_enqueue_script( 'underscore' );
	wp_localize_script( 'underscore', 'Hola_Underscores', [ 'message' => 'Hola wp_localize_script()!' ] );
	wp_add_inline_script( 'underscore', '/*Hola wp_add_inline_script( before )!*/', 'before' );
	wp_add_inline_script( 'underscore', '/*Hola wp_add_inline_script( after )!*/', 'after' );

	wp_add_inline_style( get_template() . '-style', '#add-more-inline-scripts-styled { color: red; }' );
}
add_action( 'wp_enqueue_scripts', __NAMESPACE__ . '\enqueue_assets', 20 );

add_action(
	'wp_footer',
	function () {
		echo '<div id="add-more-inline-scripts-styled">Styled by add-more-inline-scripts</div>';
	}
);