Error with duplicate operation names (#1466)

Author: JakeDawkins

CHANGELOG.md

@@ -20,6 +20,7 @@
   - <First `apollo-graphql` related entry goes here>
 - `apollo-language-server`
   - Add debugging util classes for better error/warning handling [#1429](https://github.com/apollographql/apollo-tooling/pull/1429)
+  - Add error for duplicate client operation names [#1466](https://github.com/apollographql/apollo-tooling/pull/1466)
 - `apollo-tools`
   - <First `apollo-tools` related entry goes here>
 - `vscode-apollo`

packages/apollo-language-server/src/project/base.ts

@@ -8,7 +8,8 @@ import {
   TypeSystemExtensionNode,
   isTypeSystemExtensionNode,
   DefinitionNode,
-  GraphQLSchema
+  GraphQLSchema,
+  Kind
 } from "graphql";
 
 import {
@@ -203,6 +204,7 @@ export abstract class GraphQLProject implements GraphQLSchemaProvider {
 
   fileWasDeleted(uri: DocumentUri) {
     this.removeGraphQLDocumentsFor(uri);
+    this.checkForDuplicateOperations();
   }
 
   documentDidChange(document: TextDocument) {
@@ -216,6 +218,24 @@ export abstract class GraphQLProject implements GraphQLSchemaProvider {
     } else {
       this.removeGraphQLDocumentsFor(document.uri);
     }
+    this.checkForDuplicateOperations();
+  }
+
+  checkForDuplicateOperations(): void {
+    const operations = Object.create(null);
+    for (const document of this.documents) {
+      if (!document.ast) continue;
+      for (const definition of document.ast.definitions) {
+        if (definition.kind === Kind.OPERATION_DEFINITION && definition.name) {
+          if (operations[definition.name.value]) {
+            throw new Error(
+              `️️There are multiple definitions for the ${definition.name.value} operation. All operations in a project must have unique names. If generating types, only the types for the first definition found will be generated.`
+            );
+          }
+          operations[definition.name.value] = definition;
+        }
+      }
+    }
   }
 
   private removeGraphQLDocumentsFor(uri: DocumentUri) {