Added validation rule for unique directives per location

src/Validator/DocumentValidator.php

@@ -43,6 +43,7 @@ use GraphQL\Validator\Rules\QueryComplexity;
 use GraphQL\Validator\Rules\QueryDepth;
 use GraphQL\Validator\Rules\ScalarLeafs;
 use GraphQL\Validator\Rules\UniqueArgumentNames;
+use GraphQL\Validator\Rules\UniqueDirectivesPerLocation;
 use GraphQL\Validator\Rules\UniqueFragmentNames;
 use GraphQL\Validator\Rules\UniqueInputFieldNames;
 use GraphQL\Validator\Rules\UniqueOperationNames;
@@ -88,6 +89,7 @@ class DocumentValidator
                 'NoUndefinedVariables' => new NoUndefinedVariables(),
                 'NoUnusedVariables' => new NoUnusedVariables(),
                 'KnownDirectives' => new KnownDirectives(),
+                'UniqueDirectivesPerLocation' => new UniqueDirectivesPerLocation(),
                 'KnownArgumentNames' => new KnownArgumentNames(),
                 'UniqueArgumentNames' => new UniqueArgumentNames(),
                 'ArgumentsOfCorrectType' => new ArgumentsOfCorrectType(),

src/Validator/Rules/UniqueDirectivesPerLocation.php

@@ -0,0 +1,38 @@
+<?php
+namespace GraphQL\Validator\Rules;
+
+use GraphQL\Error\Error;
+use GraphQL\Language\AST\Directive;
+use GraphQL\Language\AST\Node;
+use GraphQL\Validator\ValidationContext;
+
+class UniqueDirectivesPerLocation
+{
+    static function duplicateDirectiveMessage($directiveName)
+    {
+        return 'The directive "'.$directiveName.'" can only be used once at this location.';
+    }
+
+    public function __invoke(ValidationContext $context)
+    {
+        return [
+            'enter' => function(Node $node) use ($context) {
+                if (isset($node->directives)) {
+                    $knownDirectives = [];
+                    foreach ($node->directives as $directive) {
+                        /** @var Directive $directive */
+                        $directiveName = $directive->name->value;
+                        if (isset($knownDirectives[$directiveName])) {
+                            $context->reportError(new Error(
+                                self::duplicateDirectiveMessage($directiveName),
+                                [$knownDirectives[$directiveName], $directive]
+                            ));
+                        } else {
+                            $knownDirectives[$directiveName] = $directive;
+                        }
+                    }
+                }
+            }
+        ];
+    }
+}

tests/Validator/UniqueDirectivesPerLocationTest.php

@@ -0,0 +1,138 @@
+<?php
+namespace GraphQL\Tests\Validator;
+
+use GraphQL\Validator\Rules\UniqueDirectivesPerLocation;
+
+class UniqueDirectivesPerLocationTest extends TestCase
+{
+    /**
+     * @it no directives
+     */
+    public function testNoDirectives()
+    {
+        $this->expectPassesRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type {
+        field
+      }
+        ');
+    }
+
+    /**
+     * @it unique directives in different locations
+     */
+    public function testUniqueDirectivesInDifferentLocations()
+    {
+        $this->expectPassesRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type @directiveA {
+        field @directiveB
+      }
+        ');
+    }
+
+    /**
+     * @it unique directives in same locations
+     */
+    public function testUniqueDirectivesInSameLocations()
+    {
+        $this->expectPassesRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type @directiveA @directiveB {
+        field @directiveA @directiveB
+      }
+        ');
+    }
+
+    /**
+     * @it same directives in different locations
+     */
+    public function testSameDirectivesInDifferentLocations()
+    {
+        $this->expectPassesRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type @directiveA {
+        field @directiveA
+      }
+        ');
+    }
+
+    /**
+     * @it same directives in similar locations
+     */
+    public function testSameDirectivesInSimilarLocations()
+    {
+        $this->expectPassesRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type {
+        field @directive
+        field @directive
+      }
+        ');
+    }
+
+    /**
+     * @it duplicate directives in one location
+     */
+    public function testDuplicateDirectivesInOneLocation()
+    {
+        $this->expectFailsRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type {
+        field @directive @directive
+      }
+        ', [
+            $this->duplicateDirective('directive', 3, 15, 3, 26)
+        ]);
+    }
+
+    /**
+     * @it many duplicate directives in one location
+     */
+    public function testManyDuplicateDirectivesInOneLocation()
+    {
+        $this->expectFailsRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type {
+        field @directive @directive @directive
+      }
+        ', [
+            $this->duplicateDirective('directive', 3, 15, 3, 26),
+            $this->duplicateDirective('directive', 3, 15, 3, 37)
+        ]);
+    }
+
+    /**
+     * @it different duplicate directives in one location
+     */
+    public function testDifferentDuplicateDirectivesInOneLocation()
+    {
+        $this->expectFailsRule(new UniqueDirectivesPerLocation, '
+      fragment Test on Type {
+        field @directiveA @directiveB @directiveA @directiveB
+      }
+        ', [
+            $this->duplicateDirective('directiveA', 3, 15, 3, 39),
+            $this->duplicateDirective('directiveB', 3, 27, 3, 51)
+        ]);
+    }
+
+    /**
+     * @it duplicate directives in many locations
+     */
+    public function testDuplicateDirectivesInManyLocations()
+    {
+        $this->expectFailsRule(new UniqueDirectivesPerLocation(), '
+      fragment Test on Type @directive @directive {
+        field @directive @directive
+      }
+        ', [
+            $this->duplicateDirective('directive', 2, 29, 2, 40),
+            $this->duplicateDirective('directive', 3, 15, 3, 26)
+        ]);
+    }
+
+    private function duplicateDirective($directiveName, $l1, $c1, $l2, $c2)
+    {
+        return [
+            'message' =>UniqueDirectivesPerLocation::duplicateDirectiveMessage($directiveName),
+            'locations' => [
+                ['line' => $l1, 'column' => $c1],
+                ['line' => $l2, 'column' => $c2]
+            ]
+        ];
+    }
+}