Add support for localSchemaFile option in client config

Author: Stefan Nowak

packages/apollo-language-server/src/config.ts

@@ -65,6 +65,7 @@ export interface ClientConfigFormat extends ConfigBase {
   referenceID?: string;
   version?: string;
   // client schemas
+  localSchemaFile?: string;
   clientOnlyDirectives?: string[];
   clientSchemaDirectives?: string[];
   addTypename?: boolean;

packages/apollo-language-server/src/schema/providers/index.ts

@@ -31,7 +31,13 @@ export function schemaProviderFromConfig(
     if (typeof config.client.service === "string") {
       return new EngineSchemaProvider(config);
     }
+
+    if (config.client.localSchemaFile) {
+      return new FileSchemaProvider({ path: config.client.localSchemaFile });
+    }
+
     return new IntrospectionSchemaProvider(config.client.service);
   }
+
   throw new Error("No provider was created for config");
 }