Write tests for HEAD -/-> GET rewrite option

tests/RouterHeadToGetDisabledTest.php

@@ -0,0 +1,56 @@
+<?hh // strict
+/*
+ *  Copyright (c) 2015-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the MIT license found in the
+ *  LICENSE file in the root directory of this source tree.
+ *
+ */
+
+namespace Facebook\HackRouter;
+
+use function Facebook\FBExpect\expect;
+use type Facebook\HackRouter\Tests\NoHeadGetRewriteRouter;
+use type Facebook\HackTest\DataProvider;
+
+final class RouterHeadToGetDisabledTest extends \Facebook\HackTest\HackTest {
+  public function getAllResolvers(): vec<(
+    string,
+    (function(dict<HttpMethod, dict<string, string>>): IResolver<string>),
+  )> {
+    return vec[
+      tuple('simple regexp', $map ==> new SimpleRegexpResolver($map)),
+      tuple('prefix matching', PrefixMatchingResolver::fromFlatMap<>),
+    ];
+  }
+
+  <<DataProvider('getAllResolvers')>>
+  public function testMethodNotAllowedResponses(
+    string $_name,
+    (function(
+      dict<HttpMethod, dict<string, string>>,
+    ): IResolver<string>) $factory,
+  ): void {
+    $map = dict[
+      HttpMethod::GET => dict['/get' => 'get'],
+      HttpMethod::HEAD => dict['/head' => 'head'],
+    ];
+
+    $router = $this->getRouter()->setResolver($factory($map));
+
+    // GET -> HEAD ( no re-routing ), deviating from the default behavior.
+    $e = expect(() ==> $router->routeMethodAndPath(HttpMethod::HEAD, '/get'))
+      ->toThrow(MethodNotAllowedException::class);
+    expect($e->getAllowedMethods())->toBeSame(keyset[HttpMethod::GET]);
+
+    // GET -> HEAD
+    $e = expect(() ==> $router->routeMethodAndPath(HttpMethod::GET, '/head'))
+      ->toThrow(MethodNotAllowedException::class);
+    expect($e->getAllowedMethods())->toBeSame(keyset[HttpMethod::HEAD]);
+  }
+
+  private function getRouter(): NoHeadGetRewriteRouter<string> {
+    return new NoHeadGetRewriteRouter(dict[]);
+  }
+}

tests/lib/NoHeadGetRewriteRouter.php

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+<?hh // strict
+/*
+ *  Copyright (c) 2015-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the MIT license found in the
+ *  LICENSE file in the root directory of this source tree.
+ *
+ */
+
+namespace Facebook\HackRouter\Tests;
+
+use type Facebook\HackRouter\{BaseRouter, HttpMethod, IResolver};
+
+final class NoHeadGetRewriteRouter<T> extends BaseRouter<T> {
+  public function __construct(
+    private dict<string, T> $routes,
+    private ?IResolver<T> $resolver = null,
+  ) {
+    parent::__construct(shape('use_get_responder_for_head' => false));
+  }
+
+  <<__Override>>
+  protected function getRoutes(): ImmMap<HttpMethod, ImmMap<string, T>> {
+    return ImmMap {
+      HttpMethod::GET => new ImmMap($this->routes),
+    };
+  }
+
+  public function setResolver(IResolver<T> $resolver): this {
+    $this->resolver = $resolver;
+    return $this;
+  }
+
+  <<__Override>>
+  protected function getResolver(): IResolver<T> {
+    $r = $this->resolver;
+    if ($r === null) {
+      return parent::getResolver();
+    }
+    return $r;
+  }
+}