feature: tighten return types of config helper by using dynamic analysis

src/Handlers/Helpers/ConfigHandler.php

@@ -0,0 +1,105 @@
+<?php
+
+namespace Psalm\LaravelPlugin\Handlers\Helpers;
+
+use Illuminate\Config\Repository;
+use Psalm\LaravelPlugin\Providers\ApplicationProvider;
+use Psalm\Plugin\EventHandler\Event\FunctionReturnTypeProviderEvent;
+use Psalm\Plugin\EventHandler\FunctionReturnTypeProviderInterface;
+use Psalm\Type\Atomic\TArray;
+use Psalm\Type\Atomic\TArrayKey;
+use Psalm\Type\Atomic\TBool;
+use Psalm\Type\Atomic\TClosedResource;
+use Psalm\Type\Atomic\TFloat;
+use Psalm\Type\Atomic\TLiteralFloat;
+use Psalm\Type\Atomic\TLiteralInt;
+use Psalm\Type\Atomic\TLiteralString;
+use Psalm\Type\Atomic\TMixed;
+use Psalm\Type\Atomic\TNamedObject;
+use Psalm\Type\Atomic\TNull;
+use Psalm\Type\Atomic\TResource;
+use Psalm\Type\Union;
+
+use function gettype;
+use function get_class;
+
+class ConfigHandler implements FunctionReturnTypeProviderInterface
+{
+    public static function getFunctionIds(): array
+    {
+        return ['config'];
+    }
+
+    public static function getFunctionReturnType(FunctionReturnTypeProviderEvent $event): ?Union
+    {
+        // we're going to attempt some dynamic analysis to tighten the actual return type here.
+        // this could be done statically, but it's quicker + easier to do this dynamically.
+        // PRs to make this static in the future more than welcome!
+        $call_args = $event->getCallArgs();
+        if (!isset($call_args[0])) {
+            return new Union([
+                new TNamedObject(Repository::class),
+            ]);
+        }
+
+        $argumentType = $call_args[0]->value;
+
+        if (!isset($argumentType->value)) {
+            return null;
+        }
+
+        $argumentValue = $argumentType->value;
+
+        try {
+            // dynamic analysis
+            $returnValue = ApplicationProvider::getApp()->make('config')->get($argumentValue);
+        } catch (\Throwable $t) {
+            return null;
+        }
+
+        // turn actual return value into a psalm type. there's probably a helper in psalm to do this, but i couldn't find one
+        switch (gettype($returnValue)) {
+            case 'boolean':
+                $type = new TBool();
+                break;
+            case 'integer':
+                $type = new TLiteralInt($returnValue);
+                break;
+            case 'double':
+                $type = new TLiteralFloat($returnValue);
+                break;
+            case 'string':
+                $type = new TLiteralString($returnValue);
+                break;
+            case 'array':
+                $type = new TArray([
+                    new Union([new TArrayKey()]),
+                    new Union([new TMixed()]),
+                ]);
+                break;
+            case 'object':
+                $type = new TNamedObject(get_class($returnValue));
+                break;
+            case 'resource':
+                $type = new TResource();
+                break;
+            case 'resource (closed)':
+                $type = new TClosedResource();
+                break;
+            case 'NULL':
+                if (isset($call_args[1])) {
+                    return $event->getStatementsSource()->getNodeTypeProvider()->getType($call_args[1]->value);
+                }
+                $type = new TNull();
+                break;
+            case 'unknown type':
+            default:
+                $type = new TMixed();
+                break;
+        }
+
+        return new Union([
+            $type,
+        ]);
+    }
+}

src/Plugin.php

@@ -12,6 +12,7 @@
 use Psalm\LaravelPlugin\Handlers\Eloquent\ModelPropertyAccessorHandler;
 use Psalm\LaravelPlugin\Handlers\Eloquent\ModelRelationshipPropertyHandler;
 use Psalm\LaravelPlugin\Handlers\Eloquent\RelationsMethodHandler;
+use Psalm\LaravelPlugin\Handlers\Helpers\ConfigHandler;
 use Psalm\LaravelPlugin\Handlers\Helpers\CacheHandler;
 use Psalm\LaravelPlugin\Handlers\Helpers\PathHandler;
 use Psalm\LaravelPlugin\Handlers\Helpers\TransHandler;
@@ -135,6 +136,8 @@ private function registerHandlers(RegistrationInterface $registration): void
 
         require_once 'Handlers/SuppressHandler.php';
         $registration->registerHooksFromClass(SuppressHandler::class);
+        require_once 'Handlers/Helpers/ConfigHandler.php';
+        $registration->registerHooksFromClass(ConfigHandler::class);
     }
 
     private function generateStubFiles(): void

tests/acceptance/ConfigTypes.feature

@@ -0,0 +1,54 @@
+Feature: Config helper
+The global config helper will return a strict type
+
+Background:
+Given I have the following config
+"""
+<?xml version="1.0"?>
+<psalm errorLevel="1">
+    <projectFiles>
+        <directory name="."/>
+        <ignoreFiles> <directory name="../../vendor"/> </ignoreFiles>
+    </projectFiles>
+    <plugins>
+        <pluginClass class="Psalm\LaravelPlugin\Plugin"/>
+    </plugins>
+</psalm>
+"""
+And I have the following code preamble
+"""
+<?php declare(strict_types=1);
+
+"""
+
+Scenario: config with no arguments returns a repository instance
+  Given I have the following code
+  """
+  function test(): \Illuminate\Config\Repository {
+    return config();
+  }
+  """
+  When I run Psalm
+  Then I see no errors
+
+Scenario: config with one argument
+    Given I have the following code
+    """
+    function test(): string
+    {
+        return config('app.name');
+    }
+    """
+    When I run Psalm
+    Then I see no errors
+
+Scenario: config with first null argument and second argument provided
+    Given I have the following code
+    """
+    function test(): bool
+    {
+        return config('app.non-existent', false);
+    }
+    """
+    When I run Psalm
+    Then I see no errors