Assert non-empty-string when UUID is valid (#410)

* Assert, for psalm, the string is non-empty if validation passes
* Adds a test for SA asserting that valid string are also non-empty
* Suppress PHPStan error for unsupported conditional type assertion
* Check SA tools don't complain about non-empty-string as input parameter to `Uuid::isValid()`

phpstan-tests.neon

@@ -26,3 +26,7 @@ parameters:
                 - ./tests/Guid/*Test.php
                 - ./tests/Nonstandard/*Test.php
                 - ./tests/Rfc4122/*Test.php
+        -
+            message: "#^Method Ramsey\\\\Uuid\\\\.+ should return non-empty-string but returns string\\.$#"
+            paths:
+                - ./tests/static-analysis/ValidUuidIsNonEmpty.php

src/Uuid.php

@@ -549,6 +549,8 @@ class Uuid implements UuidInterface
      *
      * @psalm-pure note: changing the internal factory is an edge case not covered by purity invariants,
      *             but under constant factory setups, this method operates in functionally pure manners
+     *
+     * @psalm-assert-if-true non-empty-string $uuid
      */
     public static function isValid(string $uuid): bool
     {

tests/static-analysis/ValidUuidIsNonEmpty.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Ramsey\Uuid\StaticAnalysis;
+
+use InvalidArgumentException;
+use Ramsey\Uuid\Uuid;
+
+final class ValidUuidIsNonEmpty
+{
+    /** @return non-empty-string */
+    public function validUuidsAreNotEmpty(string $input): string
+    {
+        if (Uuid::isValid($input)) {
+            return $input;
+        }
+
+        throw new InvalidArgumentException('Not a UUID');
+    }
+
+    /**
+     * @param non-empty-string $input
+     *
+     * @return non-empty-string
+     */
+    public function givenNonEmptyInputAssertionRemainsValid(string $input): string
+    {
+        if (Uuid::isValid($input)) {
+            return $input;
+        }
+
+        throw new InvalidArgumentException('Not a UUID');
+    }
+}