feature: Adds UniqueFragmentNamesRule

Author: NeedleInAJayStack

Sources/GraphQL/Validation/Rules/UniqueFragmentNamesRule.swift

@@ -0,0 +1,29 @@
+
+/**
+ * Unique fragment names
+ *
+ * A GraphQL document is only valid if all defined fragments have unique names.
+ *
+ * See https://spec.graphql.org/draft/#sec-Fragment-Name-Uniqueness
+ */
+func UniqueFragmentNamesRule(context: ValidationContext) -> Visitor {
+    var knownFragmentNames = [String: Name]()
+    return Visitor(
+        enter: { node, _, _, _, _ in
+            if let fragment = node as? FragmentDefinition {
+                let fragmentName = fragment.name
+                if let knownFragmentName = knownFragmentNames[fragmentName.value] {
+                    context.report(
+                        error: GraphQLError(
+                            message: "There can be only one fragment named \"\(fragmentName.value)\".",
+                            nodes: [knownFragmentName, fragmentName]
+                        )
+                    )
+                } else {
+                    knownFragmentNames[fragmentName.value] = fragmentName
+                }
+            }
+            return .continue
+        }
+    )
+}

Sources/GraphQL/Validation/SpecifiedRules.swift

@@ -11,7 +11,7 @@ public let specifiedRules: [(ValidationContext) -> Visitor] = [
     VariablesAreInputTypesRule,
     ScalarLeafsRule,
     FieldsOnCorrectTypeRule,
-//    UniqueFragmentNamesRule,
+    UniqueFragmentNamesRule,
 //    KnownFragmentNamesRule,
     NoUnusedFragmentsRule,
     PossibleFragmentSpreadsRule,

Tests/GraphQLTests/ValidationTests/UniqueFragmentNamesRuleTests.swift

@@ -0,0 +1,130 @@
+@testable import GraphQL
+import XCTest
+
+class UniqueFragmentNamesRuleTests: ValidationTestCase {
+    override func setUp() {
+        rule = UniqueFragmentNamesRule
+    }
+
+    func testNoFragments() throws {
+        try assertValid(
+            """
+            {
+              field
+            }
+            """
+        )
+    }
+
+    func testOneFragment() throws {
+        try assertValid(
+            """
+            {
+              ...fragA
+            }
+
+            fragment fragA on Type {
+              field
+            }
+            """
+        )
+    }
+
+    func testManyFragments() throws {
+        try assertValid(
+            """
+            {
+              ...fragA
+              ...fragB
+              ...fragC
+            }
+            fragment fragA on Type {
+              fieldA
+            }
+            fragment fragB on Type {
+              fieldB
+            }
+            fragment fragC on Type {
+              fieldC
+            }
+            """
+        )
+    }
+
+    func testInlineFragmentsAreAlwaysUnique() throws {
+        try assertValid(
+            """
+            {
+              ...on Type {
+                fieldA
+              }
+              ...on Type {
+                fieldB
+              }
+            }
+            """
+        )
+    }
+
+    func testFragmentAndOperationNamedTheSame() throws {
+        try assertValid(
+            """
+            query Foo {
+              ...Foo
+            }
+            fragment Foo on Type {
+              field
+            }
+            """
+        )
+    }
+
+    func testFragmentsNamedTheSame() throws {
+        let errors = try assertInvalid(
+            errorCount: 1,
+            query:
+            """
+            {
+              ...fragA
+            }
+            fragment fragA on Type {
+              fieldA
+            }
+            fragment fragA on Type {
+              fieldB
+            }
+            """
+        )
+        try assertValidationError(
+            error: errors[0],
+            locations: [
+                (line: 4, column: 10),
+                (line: 7, column: 10),
+            ],
+            message: "There can be only one fragment named \"fragA\"."
+        )
+    }
+
+    func testFragmentsNamedTheSameWithoutBeingReferenced() throws {
+        let errors = try assertInvalid(
+            errorCount: 1,
+            query:
+            """
+            fragment fragA on Type {
+              fieldA
+            }
+            fragment fragA on Type {
+              fieldB
+            }
+            """
+        )
+        try assertValidationError(
+            error: errors[0],
+            locations: [
+                (line: 1, column: 10),
+                (line: 4, column: 10),
+            ],
+            message: "There can be only one fragment named \"fragA\"."
+        )
+    }
+}