Fix the wp_http_supports( array( 'ssl' ) ) function (#819)

Gets the `wp_http_supports()` function to return true when the `fetch()`
http transport is available.

## Rationale

`wp_http_supports` checks whether an HTTP tranport with the requests
capabilities is available. However, it does so using the
`_get_first_available_transport()` function which sources its knowledge
about HTTP transport from the `http_api_transports` filter. Therefore,
we must hook into that filter and also rename the
`Requests_Transport_Fetch` class to use the class name pattern expected
by `_get_first_available_transport()`, which is `Wp_Http_*`

## Testing instructions:

This PR ships a new E2E test – confirm it passes.

## Follow-up work

Turn the e2e test into a unit test once WordPress data modules are
easily available for import.

packages/playground/blueprints/src/lib/steps/apply-wordpress-patches/index.ts

@@ -4,7 +4,7 @@ import { updateFile } from '../common';
 import { defineWpConfigConsts } from '../define-wp-config-consts';
 
 /** @ts-ignore */
-import transportFetch from './wp-content/mu-plugins/playground-includes/requests_transport_fetch.php?raw';
+import transportFetch from './wp-content/mu-plugins/playground-includes/wp_http_fetch.php?raw';
 /** @ts-ignore */
 import transportDummy from './wp-content/mu-plugins/playground-includes/requests_transport_dummy.php?raw';
 /** @ts-ignore */
@@ -186,7 +186,7 @@ class WordPressPatcher {
 
 		// Add fetch and dummy transports for HTTP requests
 		await this.php.writeFile(
-			`${this.wordpressPath}/wp-content/mu-plugins/playground-includes/requests_transport_fetch.php`,
+			`${this.wordpressPath}/wp-content/mu-plugins/playground-includes/wp_http_fetch.php`,
 			transportFetch
 		);
 		await this.php.mkdir(`${this.wordpressPath}/wp-content/fonts`);

packages/playground/blueprints/src/lib/steps/apply-wordpress-patches/wp-content/mu-plugins/0-playground.php

@@ -81,15 +81,24 @@ function () {
  * 
  * This mu-plugin provides that transport. It's one of the two:
  * 
- * * Requests_Transport_Fetch – Sends requests using browser's fetch() function.
- *                              Only enabled when PHP was compiled with the VRZNO
- * 								extension.
+ * * WP_Http_Fetch – Sends requests using browser's fetch() function.
+ *                   Only enabled when PHP was compiled with the VRZNO
+ * 					 extension.
  * * Requests_Transport_Dummy – Does not send any requests and only exists to keep
  * 								the Requests class happy.
  */
 if (defined('USE_FETCH_FOR_REQUESTS') && USE_FETCH_FOR_REQUESTS) {
-	require(__DIR__ . '/playground-includes/requests_transport_fetch.php');
-	Requests::add_transport('Requests_Transport_Fetch');
+	require(__DIR__ . '/playground-includes/wp_http_fetch.php');
+	Requests::add_transport('WP_Http_Fetch');
+
+	/**
+	 * Add Fetch transport to the list of transports that WordPress
+	 * will test for in the _get_first_available_transport() function.
+	 */
+	add_filter('http_api_transports', function ($transports) {
+		$transports[] = 'Fetch';
+		return $transports;
+	});
 	/**
 	 * Disable signature verification as it doesn't seem to work with
 	 * fetch requests:

packages/playground/blueprints/src/lib/steps/apply-wordpress-patches/wp-content/mu-plugins/playground-includes/requests_transport_fetch.php → packages/playground/blueprints/src/lib/steps/apply-wordpress-patches/wp-content/mu-plugins/playground-includes/wp_http_fetch.php

@@ -6,8 +6,13 @@
  * This file isn't actually used. It's just here for reference and development. The actual
  * PHP code used in WordPress is hardcoded copy residing in wordpress.mjs in the _patchWordPressCode
  * function.
+ * 
+ * The reason for calling it Wp_Http_Fetch and not something more natural like
+ * Requests_Transport_Fetch is the _get_first_available_transport(). It checks for
+ * a class named "Wp_Http_" . $transport_name – which means we must adhere to this
+ * hardcoded pattern.
  */
-class Requests_Transport_Fetch implements Requests_Transport
+class Wp_Http_Fetch implements Requests_Transport
 {
 	public $headers = '';
 

packages/playground/website/cypress/e2e/app.cy.ts

@@ -70,6 +70,32 @@ describe('Query API', () => {
 				.find('.plugin-card')
 				.should('have.length.above', 4);
 		});
+
+		/**
+		 * @see https://github.com/WordPress/wordpress-playground/pull/819
+		 * @TODO: Turn this into a unit test once WordPress modules are available
+		 *        for import.
+		 */
+		it('should return true from wp_http_supports(array( "ssl" ))', () => {
+			const blueprint = {
+				landingPage: '/test.php',
+				features: {
+					networking: true,
+				},
+				steps: [
+					{
+						step: 'writeFile',
+						path: '/wordpress/test.php',
+						data: `<?php 
+						require("/wordpress/wp-load.php");
+						echo wp_http_supports(array( "ssl" )) ? "true" : "false";
+						`,
+					},
+				],
+			};
+			cy.visit('/#' + JSON.stringify(blueprint));
+			cy.wordPressDocument().its('body').should('contain', 'true');
+		});
 	});
 
 	describe('option `plugin`', () => {
@@ -211,6 +237,7 @@ if (!Cypress.env('CI')) {
 				.should('contain', 'Cypress tests – site title');
 
 			// Download a zip file
+			const downloadsFolder = Cypress.config('downloadsFolder');
 			cy.get('[data-cy="dropdown-menu"]').click();
 			cy.get('[data-cy="download-as-zip"]').click();
 			cy.readFile(downloadsFolder + '/wordpress-playground.zip').should(
@@ -229,7 +256,6 @@ if (!Cypress.env('CI')) {
 			// Import the zip file
 			cy.get('[data-cy="dropdown-menu"]').click();
 			cy.get('[data-cy="restore-from-zip"]').click();
-			const downloadsFolder = Cypress.config('downloadsFolder');
 			cy.get('#import-select-file').selectFile(
 				`${downloadsFolder}/wordpress-playground.zip`
 			);