fix(federation): relaxes @requires and @external constraints (#1778)

Relaxing `@requires` and `@external` constraints. Previously ALL fields referenced from the `@requires` selection set had to be marked `@external`. This was too strict as it is possible to define `@requires` selection set against **local** object type with some `@external` fields. As a result only leaf fields (i.e. scalar/enum fields) have to be explicitly marked `@external` OR implicitly inherit `@external` characteristic through any of the leaf field ancestors.

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/validation/ValidateFieldSelection.kt

@@ -26,7 +26,7 @@ import graphql.schema.GraphQLType
 import graphql.schema.GraphQLTypeUtil
 import graphql.schema.GraphQLUnionType
 
-internal fun validateFieldSelection(validatedDirective: DirectiveInfo, selection: FieldSetSelection, targetType: GraphQLType, errors: MutableList<String>) {
+internal fun validateFieldSelection(validatedDirective: DirectiveInfo, selection: FieldSetSelection, targetType: GraphQLType, errors: MutableList<String>, isExternalPath: Boolean = false) {
     when (val unwrapped = GraphQLTypeUtil.unwrapNonNull(targetType)) {
         is GraphQLScalarType, is GraphQLEnumType -> {
             if (selection.subSelections.isNotEmpty()) {
@@ -38,7 +38,7 @@ internal fun validateFieldSelection(validatedDirective: DirectiveInfo, selection
             if (KEY_DIRECTIVE_NAME == validatedDirective.directiveName) {
                 errors.add("$validatedDirective specifies invalid field set - field set references GraphQLList, field=${selection.field}")
             } else {
-                validateFieldSelection(validatedDirective, selection, GraphQLTypeUtil.unwrapOne(targetType), errors)
+                validateFieldSelection(validatedDirective, selection, GraphQLTypeUtil.unwrapOne(targetType), errors, isExternalPath)
             }
         }
         is GraphQLInterfaceType -> {
@@ -51,7 +51,8 @@ internal fun validateFieldSelection(validatedDirective: DirectiveInfo, selection
                     validatedDirective,
                     selection.subSelections,
                     unwrapped.fieldDefinitions.associateBy { it.name },
-                    errors
+                    errors,
+                    isExternalPath
                 )
             }
         }
@@ -63,7 +64,8 @@ internal fun validateFieldSelection(validatedDirective: DirectiveInfo, selection
                     validatedDirective,
                     selection.subSelections,
                     unwrapped.fieldDefinitions.associateBy { it.name },
-                    errors
+                    errors,
+                    isExternalPath
                 )
             }
         }

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/validation/validateDirective.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 Expedia, Inc
+ * Copyright 2023 Expedia, Inc
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,7 @@ internal fun validateDirective(
     validatedType: String,
     targetDirective: String,
     directiveMap: Map<String, List<GraphQLAppliedDirective>>,
-    fieldMap: Map<String, GraphQLFieldDefinition>,
+    fieldMap: Map<String, GraphQLFieldDefinition>
 ): List<String> {
     val validationErrors = mutableListOf<String>()
     val directives = directiveMap[targetDirective]

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/validation/validateFieldSetSelection.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 Expedia, Inc
+ * Copyright 2023 Expedia, Inc
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,24 +18,32 @@ package com.expediagroup.graphql.generator.federation.validation
 
 import com.expediagroup.graphql.generator.federation.directives.EXTERNAL_DIRECTIVE_NAME
 import com.expediagroup.graphql.generator.federation.directives.REQUIRES_DIRECTIVE_NAME
+import graphql.schema.GraphQLDirectiveContainer
 import graphql.schema.GraphQLFieldDefinition
+import graphql.schema.GraphQLNamedType
+import graphql.schema.GraphQLTypeUtil
 
 internal fun validateFieldSetSelection(
     validatedDirective: DirectiveInfo,
     selections: List<FieldSetSelection>,
     fields: Map<String, GraphQLFieldDefinition>,
-    errors: MutableList<String>
+    errors: MutableList<String>,
+    isExternalPath: Boolean = false
 ) {
     for (selection in selections) {
         val currentField = fields[selection.field]
         if (currentField == null) {
             errors.add("$validatedDirective specifies invalid field set - field set specifies field that does not exist, field=${selection.field}")
         } else {
             val currentFieldType = currentField.type
-            if (REQUIRES_DIRECTIVE_NAME == validatedDirective.directiveName && currentField.getAppliedDirective(EXTERNAL_DIRECTIVE_NAME) == null) {
+            val isExternal = isExternalPath || GraphQLTypeUtil.unwrapAll(currentFieldType).isExternalPath() || currentField.isExternalType()
+            if (REQUIRES_DIRECTIVE_NAME == validatedDirective.directiveName && GraphQLTypeUtil.isLeaf(currentFieldType) && !isExternal) {
                 errors.add("$validatedDirective specifies invalid field set - @requires should reference only @external fields, field=${selection.field}")
             }
-            validateFieldSelection(validatedDirective, selection, currentFieldType, errors)
+            validateFieldSelection(validatedDirective, selection, currentFieldType, errors, isExternal)
         }
     }
 }
+
+private fun GraphQLDirectiveContainer.isExternalType(): Boolean = this.getAppliedDirectives(EXTERNAL_DIRECTIVE_NAME).isNotEmpty()
+private fun GraphQLNamedType.isExternalPath(): Boolean = this is GraphQLDirectiveContainer && this.isExternalType()

generator/graphql-kotlin-federation/src/test/kotlin/com/expediagroup/graphql/generator/federation/data/integration/requires/success/_5/LeafRequires.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2023 Expedia, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.expediagroup.graphql.generator.federation.data.integration.requires.success._5
+
+import com.expediagroup.graphql.generator.federation.directives.ExternalDirective
+import com.expediagroup.graphql.generator.federation.directives.FieldSet
+import com.expediagroup.graphql.generator.federation.directives.KeyDirective
+import com.expediagroup.graphql.generator.federation.directives.RequiresDirective
+import kotlin.properties.Delegates
+
+/*
+# only leaf fields have to be external when @requires references complex types
+type LeafRequires @key(fields : "id") {
+  complexType: ComplexType!
+  description: String!
+  id: String!
+  shippingCost: String! @requires(fields : "complexType { weight }")
+}
+
+type ComplexType {
+  localField: String
+  weight: Float! @external
+}
+ */
+@KeyDirective(fields = FieldSet("id"))
+class LeafRequires(val id: String, val description: String, val complexType: ComplexType) {
+
+    @RequiresDirective(FieldSet("complexType { weight }"))
+    fun shippingCost(): String = "$${complexType.weight * 9.99}"
+}
+
+class ComplexType(val localField: String) {
+    @ExternalDirective
+    var weight: Double by Delegates.notNull()
+}

generator/graphql-kotlin-federation/src/test/kotlin/com/expediagroup/graphql/generator/federation/data/integration/requires/success/_6/RecursiveExternalRequires.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2023 Expedia, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.expediagroup.graphql.generator.federation.data.integration.requires.success._6
+
+import com.expediagroup.graphql.generator.federation.directives.ExternalDirective
+import com.expediagroup.graphql.generator.federation.directives.FieldSet
+import com.expediagroup.graphql.generator.federation.directives.KeyDirective
+import com.expediagroup.graphql.generator.federation.directives.RequiresDirective
+import kotlin.properties.Delegates
+
+/*
+# @external information is applied recursively through parent fields
+type RecursiveExternalRequires @key(fields : "id") {
+  complexType: ComplexType! @external
+  description: String!
+  id: String!
+  shippingCost: String! @requires(fields : "complexType { weight }")
+}
+
+type ComplexType {
+  potentiallyExternal: String
+  weight: Float!
+}
+ */
+@KeyDirective(fields = FieldSet("id"))
+class RecursiveExternalRequires(val id: String, val description: String, @ExternalDirective val complexType: ComplexType) {
+
+    @RequiresDirective(FieldSet("complexType { weight }"))
+    fun shippingCost(): String = "$${complexType.weight * 9.99}"
+}
+
+class ComplexType(val potentiallyExternal: String) {
+    var weight: Double by Delegates.notNull()
+}

generator/graphql-kotlin-federation/src/test/kotlin/com/expediagroup/graphql/generator/federation/data/integration/requires/success/_7/ExternalRequiresType.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2023 Expedia, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.expediagroup.graphql.generator.federation.data.integration.requires.success._7
+
+import com.expediagroup.graphql.generator.federation.directives.ExternalDirective
+import com.expediagroup.graphql.generator.federation.directives.FieldSet
+import com.expediagroup.graphql.generator.federation.directives.KeyDirective
+import com.expediagroup.graphql.generator.federation.directives.RequiresDirective
+import kotlin.properties.Delegates
+
+/*
+# @external information is applied to fields within type
+type RecursiveExternalRequires @key(fields : "id") {
+  externalType: ExternalType!
+  description: String!
+  id: String!
+  shippingCost: String! @requires(fields : "complexType { weight }")
+}
+
+type ExternalType @external {
+  allExternal: String
+  weight: Float!
+}
+ */
+@KeyDirective(fields = FieldSet("id"))
+class ExternalRequiresType(val id: String, val description: String, val externalType: ExternalType) {
+
+    @RequiresDirective(FieldSet("externalType { weight }"))
+    fun shippingCost(): String = "$${externalType.weight * 9.99}"
+}
+
+@ExternalDirective
+class ExternalType(val allExternal: String) {
+    var weight: Double by Delegates.notNull()
+}