Allow multiple @link schema extensions (#6284)

* Allow multiple @link schema extensions

* Make getImports return the foreign schema for @link

Author: BoD

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/SchemaValidationScope.kt

@@ -318,15 +318,20 @@ private fun List<GQLSchemaExtension>.getImports(
   val schemaExtensions = this
 
   val imports = mutableListOf<Import>()
-
+  val linkForeignSchema = ForeignSchema("link", "v1.0", linkDefinitions())
+  val linkImport = Import(linkForeignSchema, linkForeignSchema.definitions, mapOf("link" to "link"))
   schemaExtensions.forEach { schemaExtension ->
     schemaExtension.directives.forEach eachDirective@{ gqlDirective ->
       if (gqlDirective.name == "link") {
+        if (!imports.contains(linkImport)) {
+          imports.add(linkImport)
+        }
+
         /**
          * Validate `@link` using a very minimal schema.
          * This ensure we can safely cast the arguments below
          */
-        val minimalSchema = builtinDefinitions + linkDefinitions()
+        val minimalSchema = builtinDefinitions + linkForeignSchema.definitions
         val scope = DefaultValidationScope(
             minimalSchema.filterIsInstance<GQLTypeDefinition>().associateBy { it.name },
             minimalSchema.filterIsInstance<GQLDirectiveDefinition>().associateBy { it.name },

libraries/apollo-ast/src/commonTest/kotlin/com/apollographql/apollo/graphql/ast/test/SchemaTest.kt

@@ -73,6 +73,40 @@ class SchemaTest {
     assertEquals("cacheControl", schema.originalDirectiveName("cacheControl"))
   }
 
+  @Test
+  fun multipleImportDirectives() {
+    // language=graphql
+    val schemaString = """
+      extend schema
+      @link(url: "https://specs.apollo.dev/cache/v0.1/", import: ["@cacheControl"])
+      @link(url: "https://example.com/example/v0.1/", import: ["@example"])
+      extend schema
+      @link(url: "https://example.com/example2/v0.1/", import: ["@example2"])
+
+      type Query {
+        foo: Int @cacheControl(maxAge: 100) @example @example2
+      }
+    """.trimIndent()
+
+    val schema = schemaString.toGQLDocument().validateAsSchema(
+        SchemaValidationOptions(
+            addKotlinLabsDefinitions = false,
+            foreignSchemas = listOf(
+                cacheControlSchema,
+                ForeignSchema("example", "v0.1",
+                    listOf("directive @example on FIELD_DEFINITION".parseAsGQLDocument().getOrThrow().definitions.single())
+                ),
+                ForeignSchema("example2", "v0.1",
+                    listOf("directive @example2 on FIELD_DEFINITION".parseAsGQLDocument().getOrThrow().definitions.single())
+                )
+            )
+        )
+    ).getOrThrow()
+
+    assertEquals("cacheControl", schema.originalDirectiveName("cacheControl"))
+    assertEquals("example", schema.originalDirectiveName("example"))
+  }
+
   @Test
   fun unknownSchemaFails() {
     // language=graphql