PHPLIB-831: Allow $$exists within $$unsetOrMatches

tests/UnifiedSpecTests/Constraint/Matches.php

@@ -24,6 +24,7 @@
 use function is_float;
 use function is_int;
 use function is_object;
+use function ltrim;
 use function PHPUnit\Framework\assertIsBool;
 use function PHPUnit\Framework\assertIsString;
 use function PHPUnit\Framework\assertMatchesRegularExpression;
@@ -37,6 +38,7 @@
 use function range;
 use function sprintf;
 use function strpos;
+use function strrchr;
 
 use const PHP_INT_SIZE;
 
@@ -240,6 +242,19 @@ private function assertMatchesOperator(BSONDocument $operator, $actual, string $
     {
         $name = self::getOperatorName($operator);
 
+        if ($name === '$$exists') {
+            assertIsBool($operator['$$exists'], '$$exists requires bool');
+
+            /* If we get to this point, the field itself must already exist so
+             * we need only fail if $$exists is false. */
+            if ($operator['$$exists'] === false) {
+                $key = ltrim(strrchr($keyPath, '.'), '.');
+                self::failAt(sprintf('$actual has unexpected key "%s"', $key), $keyPath);
+            }
+
+            return;
+        }
+
         if ($name === '$$type') {
             assertThat(
                 $operator['$$type'],

tests/UnifiedSpecTests/Constraint/MatchesTest.php

@@ -119,6 +119,26 @@ public function testOperatorUnsetOrMatches(): void
         $this->assertResult(false, $c, ['x' => ['y' => 1, 'z' => 2]], 'value does not match (embedded)');
     }
 
+    public function testOperatorUnsetOrMatchesWithNestedOperator(): void
+    {
+        // Nested $$unsetOrMatches is redundant, but should behave the same as if it was omitted
+        $c = new Matches(['x' => ['$$unsetOrMatches' => ['$$unsetOrMatches' => ['y' => 1]]]]);
+        $this->assertResult(true, $c, new stdClass(), 'missing value is considered unset (embedded)');
+        $this->assertResult(false, $c, ['x' => null], 'null value is not considered unset (embedded)');
+        $this->assertResult(true, $c, ['x' => ['y' => 1]], 'value matches (embedded)');
+        $this->assertResult(false, $c, ['x' => ['y' => 1, 'z' => 2]], 'value does not match (embedded)');
+
+        $c = new Matches(['x' => ['$$unsetOrMatches' => ['$$exists' => true]]]);
+        $this->assertResult(true, $c, new stdClass(), 'missing value is considered unset (embedded)');
+        $this->assertResult(true, $c, ['x' => null], 'null value is not considered unset (embedded)');
+        $this->assertResult(true, $c, ['x' => ['y' => 1]], 'non-null value is not considered unset (embedded)');
+
+        $c = new Matches(['x' => ['$$unsetOrMatches' => ['$$exists' => false]]]);
+        $this->assertResult(true, $c, new stdClass(), 'missing value is considered unset (embedded)');
+        $this->assertResult(false, $c, ['x' => null], 'null value is not considered unset (embedded)');
+        $this->assertResult(false, $c, ['x' => ['y' => 1]], 'non-null value is not considered unset (embedded)');
+    }
+
     public function testOperatorSessionLsid(): void
     {
         $session = $this->manager->startSession();