Add composer dependencies, add code analyser service and form to trigger code analyser

composer.json

+{
+    "name": "drupal/upgrade_status",
+    "type": "drupal-module",
+    "description": "Tool to review deprecation status.",
+    "homepage": "http://drupal.org/project/upgrade_status",
+    "license": "GPL-2.0-or-later",
+    "require": {
+        "drupal/core": "^8.6",
+        "mglaman/phpstan-drupal": "^0.12.0@dev",
+        "mglaman/phpstan-drupal-deprecations": "^0.11.1",
+        "mglaman/phpstan-junit": "^0.11.1",
+        "phpstan/phpstan-deprecation-rules": "^0.11.0@dev"
+    },
+    "minimum-stability": "dev"
+}

deprecation_testing.neon

+parameters:
+	excludes_analyse:
+		- *.api.php
+		- */tests/Drupal/Tests/Listeners/Legacy/*
+		- */tests/fixtures/*.php
+	customRulesetUsed: true
+	# Ignore phpstan-drupal extension's rules.
+	fileExtensions:
+		- module
+		- theme
+		- inc
+	ignoreErrors:
+		- '#\Drupal calls should be avoided in classes, use dependency injection instead#'
+		- '#Plugin definitions cannot be altered.#'
+		- '#Missing cache backend declaration for performance.#'
+		- '#Plugin manager has cache backend specified but does not declare cache tags.#'
+	reportUnmatchedIgnoredErrors: false
+	# Ignore tests
+extensions:
+	drupal: PHPStan\DependencyInjection\DrupalExtension
+drupal:
+	entityTypeStorageMapping:
+		node: Drupal\node\NodeStorage
+		taxonomy_term: Drupal\taxonomy\TermStorage
+		user: Drupal\user\UserStorage
+rules:
+	- PHPStan\Rules\Classes\PluginManagerInspectionRule
+	- PHPStan\Rules\Drupal\Coder\DiscouragedFunctionsRule
+	- PHPStan\Rules\Drupal\GlobalDrupalDependencyInjectionRule
+	- PHPStan\Rules\Drupal\PluginManager\PluginManagerSetsCacheBackendRule
+	- PHPStan\Rules\Deprecations\AccessDeprecatedPropertyRule
+	- PHPStan\Rules\Deprecations\AccessDeprecatedStaticPropertyRule
+	- PHPStan\Rules\Deprecations\CallToDeprecatedFunctionRule
+	- PHPStan\Rules\Deprecations\CallToDeprecatedMethodRule
+	- PHPStan\Rules\Deprecations\CallToDeprecatedStaticMethodRule
+	- PHPStan\Rules\Deprecations\FetchingClassConstOfDeprecatedClassRule
+	- PHPStan\Rules\Deprecations\ImplementationOfDeprecatedInterfaceRule
+	- PHPStan\Rules\Deprecations\InheritanceOfDeprecatedClassRule
+	- PHPStan\Rules\Deprecations\InheritanceOfDeprecatedInterfaceRule
+	- PHPStan\Rules\Deprecations\InstantiationOfDeprecatedClassRule
+	- PHPStan\Rules\Deprecations\UsageOfDeprecatedTraitRule
+services:
+	drupal.serviceMapFactory:
+		class: PHPStan\Drupal\ServiceMapFactoryInterface
+		factory: PHPStan\Drupal\ServiceMapFactory(%drupalServiceMap%)
+	-
+		class: @drupal.serviceMapFactory::create()
+	-
+		class: PHPStan\Type\EntityTypeManagerGetStorageDynamicReturnTypeExtension
+		arguments:
+			entityTypeStorageMapping: %drupal.entityTypeStorageMapping%
+		tags: [phpstan.broker.dynamicMethodReturnTypeExtension]
+	-
+		class: PHPStan\Type\ServiceDynamicReturnTypeExtension
+		tags: [phpstan.broker.dynamicMethodReturnTypeExtension]
+	errorFormatter.junit:
+		class: PHPStan\Command\ErrorFormatter\JUnitErrorFormatter

src/DeprecationAnalyser.php

+<?php
+
+namespace Drupal\upgrade_status;
+
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Logger\LoggerChannelFactoryInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use PHPStan\Command\AnalyseApplication;
+use PHPStan\Command\CommandHelper;
+use PHPStan\Command\ErrorFormatter\ErrorFormatter;
+use PHPStan\Command\InceptionNotSuccessfulException;
+use PHPStan\ShouldNotHappenException;
+use Symfony\Component\Console\Input\StringInput;
+use Symfony\Component\Console\Output\BufferedOutput;
+
+class DeprecationAnalyser {
+
+  use StringTranslationTrait;
+
+  const ERROR_FORMAT = 'json';
+
+  /**
+   * @var \Drupal\Core\Cache\CacheBackendInterface
+   */
+  private $cache;
+
+  /**
+   * @var \Drupal\Core\Logger\LoggerChannelInterface
+   */
+  private $logger;
+
+  /**
+   * DeprecationAnalyser constructor.
+   *
+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache
+   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $loggerFactory
+   */
+  public function __construct(
+    CacheBackendInterface $cache,
+    LoggerChannelFactoryInterface $loggerFactory
+  ) {
+    $this->cache = $cache;
+    $this->logger = $loggerFactory->get('readiness');
+  }
+
+  public function analyse() {
+    $modulePath = drupal_get_path('module', 'upgrade_status');
+
+    if (!isset($GLOBALS['autoloaderInWorkingDirectory'])) {
+      $GLOBALS['autoloaderInWorkingDirectory'] = implode(DIRECTORY_SEPARATOR, [DRUPAL_ROOT, 'autoload.php']);
+    }
+
+    $errorOutput = new BufferedOutput();
+    $configuration = implode(DIRECTORY_SEPARATOR, [DRUPAL_ROOT, $modulePath, 'deprecation_testing.neon']);
+
+    $files = [];
+    $files[] = implode(DIRECTORY_SEPARATOR, [DRUPAL_ROOT, 'core/lib/Drupal.php']);
+
+    try {
+      $inspectionResult = CommandHelper::begin(
+        new StringInput('analyse'),
+        $errorOutput,
+        $files,
+        null,
+        null,
+        null,
+        $configuration,
+        null
+      );
+    } catch (InceptionNotSuccessfulException $e) {
+      $this->logger->error($e);
+    } catch (ShouldNotHappenException $e) {
+      $this->logger->error($e);
+    }
+
+    $container = $inspectionResult->getContainer();
+    $errorFormatterServiceName = sprintf('errorFormatter.%s', self::ERROR_FORMAT);
+    if (!$container->hasService($errorFormatterServiceName)) {
+      $this->logger->error($this->t('Error formatter @formatter not found'), ['@formatter' => self::ERROR_FORMAT]);
+      return '';
+    }
+
+    /** @var ErrorFormatter $errorFormatter */
+    $errorFormatter = $container->getService($errorFormatterServiceName);
+    $application = $container->getByType(AnalyseApplication::class);
+
+    $inspectionResult->handleReturn(
+      $application->analyse(
+        $inspectionResult->getFiles(),
+        $inspectionResult->isOnlyFiles(),
+        $inspectionResult->getConsoleStyle(),
+        $errorFormatter,
+        $inspectionResult->isDefaultLevelUsed(),
+        FALSE
+      )
+    );
+
+    return $errorOutput->fetch();
+  }
+
+}

src/DeprecationAnalyserInterface.php

+<?php
+
+interface DeprecationAnalyserInterface {
+
+  public function analyse(): array;
+
+}

src/Form/ReadinessForm.php

+<?php
+
+namespace Drupal\upgrade_status\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\upgrade_status\DeprecationAnalyser;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+class ReadinessForm extends FormBase {
+
+  /**
+   * @var \Drupal\upgrade_status\DeprecationAnalyser
+   */
+  protected $deprecationAnalyser;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('upgrade_status.deprecation_analyser')
+    );
+  }
+
+  /**
+   * ReadinessForm constructor.
+   *
+   * @param \Drupal\upgrade_status\DeprecationAnalyser $deprecationAnalyser
+   */
+  public function __construct(DeprecationAnalyser $deprecationAnalyser) {
+    $this->deprecationAnalyser = $deprecationAnalyser;
+  }
+
+    /**
+   * Returns a unique string identifying the form.
+   *
+   * The returned ID should be a unique string that can be a valid PHP function
+   * name, since it's used in hook implementation names such as
+   * hook_form_FORM_ID_alter().
+   *
+   * @return string
+   *   The unique string identifying the form.
+   */
+  public function getFormId() {
+    return 'drupal_readiness_form';
+  }
+
+  /**
+   * Form constructor.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return array
+   *   The form structure.
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $data = $form_state->get('deprecation_data');
+
+    $form['drupal_readiness_form'] = [
+      'response' => [
+        '#type' => 'details',
+        '#title' => $this->t('Response'),
+        '#tree' => TRUE,
+        '#open' => TRUE,
+        'data' => [
+          '#type' => '#markup',
+          '#markup' => $data,
+        ],
+      ],
+    ];
+
+    $form['drupal_readiness_form']['action']['submit'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Analyse'),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * Form submission handler.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $form_state->setRebuild(TRUE);
+
+    $form_state->set('deprecation_data', $this->deprecationAnalyser->analyse());
+  }
+
+}

upgrade_status.routing.yml

+upgrade_status.analyse:
+  path: '/admin/reports/updates/deprecations'
+  defaults:
+    _title: 'Drupal 9 Readiness'
+    _form: 'Drupal\upgrade_status\Form\ReadinessForm'
+  requirements:
+    _permission: 'administer site configuration'

upgrade_status.services.yml

+services:
+  upgrade_status.deprecation_analyser:
+    class: Drupal\upgrade_status\DeprecationAnalyser
+    arguments: ['@cache.default', '@logger.factory']