bug #50530 [DependencyInjection] Fix support for false boolean env vars (Okhoshi)

This PR was merged into the 6.3 branch.

Discussion
----------

[DependencyInjection] Fix support for `false` boolean env vars

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

After upgrading `symfony/dependency-injection` package to version 6.3, some of our env vars couldn't be found anymore.

For some scripts, we are providing an adhoc default value to env vars by setting `$_SERVER` directly. However, since version 6.3 of the DependencyInjection component, setting an env var to `false` (the boolean value, like in the snippet below) doesn't work anymore, and Symfony reports that the variable cannot be found.

```php
$_SERVER['FOO'] = false;
```

It seems to be a side effect of the changes made in #48705.

Commits
-------

5101d188c4 [DependencyInjection] Fix support for `false` boolean env vars

Author: nicolas-grekas

EnvVarProcessor.php

@@ -146,7 +146,7 @@ public function getEnv(string $prefix, string $name, \Closure $getEnv): mixed
         if (false !== $i || 'string' !== $prefix) {
             $env = $getEnv($name);
         } elseif ('' === ($env = $_ENV[$name] ?? (str_starts_with($name, 'HTTP_') ? null : ($_SERVER[$name] ?? null)))
-            || false === ($env = $env ?? getenv($name) ?? false) // null is a possible value because of thread safety issues
+            || (false !== $env && false === ($env = $env ?? getenv($name) ?? false)) // null is a possible value because of thread safety issues
         ) {
             foreach ($this->loadedVars as $vars) {
                 if (false !== ($env = ($vars[$name] ?? $env)) && '' !== $env) {

Tests/EnvVarProcessorTest.php

@@ -59,6 +59,67 @@ public static function validStrings()
         ];
     }
 
+    /**
+     * @dataProvider validRealEnvValues
+     */
+    public function testGetEnvRealEnv($value, $processed)
+    {
+        $_ENV['FOO'] = $value;
+
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('string', 'FOO', function () {
+            $this->fail('Should not be called');
+        });
+
+        $this->assertSame($processed, $result);
+
+        unset($_ENV['FOO']);
+    }
+
+    public static function validRealEnvValues()
+    {
+        return [
+            ['hello', 'hello'],
+            [true, '1'],
+            [false, ''],
+            [1, '1'],
+            [0, '0'],
+            [1.1, '1.1'],
+            [10, '10'],
+        ];
+    }
+
+    public function testGetEnvRealEnvInvalid()
+    {
+        $_ENV['FOO'] = null;
+        $this->expectException(EnvNotFoundException::class);
+        $this->expectExceptionMessage('Environment variable not found: "FOO".');
+
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('string', 'FOO', function () {
+            $this->fail('Should not be called');
+        });
+
+        unset($_ENV['FOO']);
+    }
+
+    public function testGetEnvRealEnvNonScalar()
+    {
+        $_ENV['FOO'] = [];
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Non-scalar env var "FOO" cannot be cast to "string".');
+
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('string', 'FOO', function () {
+            $this->fail('Should not be called');
+        });
+
+        unset($_ENV['FOO']);
+    }
+
     /**
      * @dataProvider validBools
      */
@@ -97,6 +158,7 @@ public static function validBools()
             ['true', true],
             ['false', false],
             ['null', false],
+            ['', false],
             ['1', true],
             ['0', false],
             ['1.1', true],