Don't add duplicate field names

CHANGELOG.md

@@ -6,6 +6,7 @@ Expect active development and potentially significant breaking changes in the `0
 
 - Move out GraphQL query parsing into a new package [`graphql-tag`](https://github.com/apollostack/graphql-tag) with a backcompat shim for `apollo-client/gql`. [Issue #312](https://github.com/apollostack/apollo-client/issues/312) [PR #313](https://github.com/apollostack/apollo-client/pull/313)
 - Added `ssrMode` (to disable `forceFetch` queries completely) and `ssrForceFetchDelay` (to disable it for a short time period). This is for server-side rendering -- on the server it doesn't make sense to force fetch (you just want a single snapshot of data, not changing data), and when you first re-render on the client, the server's data is up to date, so there's no need to re-fetch. [Issue #298](https://github.com/apollostack/apollo-client/issues/298) [PR #309](https://github.com/apollostack/apollo-client/pull/309)
+- `addTypename` query transform now doesn't add extra `__typename` fields where they are already present. [PR #323](https://github.com/apollostack/apollo-client/pull/323)
 
 ### v0.3.20
 

src/queries/queryTransform.ts

@@ -8,16 +8,16 @@ import {
 import cloneDeep = require('lodash.clonedeep');
 
 // A QueryTransformer takes a SelectionSet and transforms it in someway (in place).
-export type QueryTransformer = (queryPiece: SelectionSet) => void
+export type QueryTransformer = (selectionSet: SelectionSet) => void
 
 // Adds a field with a given name to every node in the AST recursively.
 // Note: this mutates the AST passed in.
-export function addFieldToSelectionSet(fieldName: string, queryPiece: SelectionSet) {
-  if (queryPiece == null || queryPiece.selections == null) {
-    return queryPiece;
+export function addFieldToSelectionSet(fieldName: string, selectionSet: SelectionSet) {
+  if (selectionSet == null || selectionSet.selections == null) {
+    return selectionSet;
   }
 
-  const typenameFieldAST: Field = {
+  const fieldAst: Field = {
     kind: 'Field',
     alias: null,
     name: {
@@ -26,23 +26,31 @@ export function addFieldToSelectionSet(fieldName: string, queryPiece: SelectionS
     },
   };
 
-  queryPiece.selections.map((child) => {
-    // We use type assertions to make sure the child isn't a FragmentSpread because
+  let alreadyHasThisField = false;
+  selectionSet.selections.map((selection) => {
+    // We use type assertions to make sure the selection isn't a FragmentSpread because
     // that can't have a selectionSet.
-    if (child.kind === 'Field' || child.kind === 'InlineFragment') {
-      addTypenameToSelectionSet((child as (Field | InlineFragment)).selectionSet);
+    if (selection.kind === 'Field' || selection.kind === 'InlineFragment') {
+      addTypenameToSelectionSet((selection as (Field | InlineFragment)).selectionSet);
+    }
+
+    if (selection.kind === 'Field' && (selection as Field).name.value === fieldName) {
+      alreadyHasThisField = true;
     }
   });
 
-  // Add the typename to this particular node's children
-  queryPiece.selections.push(typenameFieldAST);
-  return queryPiece;
+  if (! alreadyHasThisField) {
+    // Add the typename to this particular node's children
+    selectionSet.selections.push(fieldAst);
+  }
+
+  return selectionSet;
 }
 
 // Adds typename fields to every node in the AST recursively.
 // Note: This muates the AST passed in.
-export function addTypenameToSelectionSet(queryPiece: SelectionSet) {
-  return addFieldToSelectionSet('__typename', queryPiece);
+export function addTypenameToSelectionSet(selectionSet: SelectionSet) {
+  return addFieldToSelectionSet('__typename', selectionSet);
 }
 
 // Add typename field to the root query node (i.e. OperationDefinition). Returns a new

test/queryTransform.ts

@@ -22,7 +22,7 @@ describe('query transforms', () => {
           }
         }
       }
-`;
+    `;
     const queryDef = getQueryDefinition(testQuery);
     const queryRes = addTypenameToSelectionSet(queryDef.selectionSet);
 
@@ -39,7 +39,45 @@ describe('query transforms', () => {
           }
           __typename
         }
-        __typename}`);
+        __typename
+      }
+    `);
+    const expectedQueryStr = print(expectedQuery);
+
+    assert.equal(expectedQueryStr, modifiedQueryStr);
+  });
+
+  it('should not add duplicates', () => {
+    let testQuery = gql`
+      query {
+        author {
+          name {
+            firstName
+            lastName
+            __typename
+          }
+        }
+      }
+    `;
+    const queryDef = getQueryDefinition(testQuery);
+    const queryRes = addTypenameToSelectionSet(queryDef.selectionSet);
+
+    // GraphQL print the parsed, updated query and replace the trailing
+    // newlines.
+    const modifiedQueryStr = print(queryRes);
+    const expectedQuery = getQueryDefinition(gql`
+      query {
+        author {
+          name {
+            firstName
+            lastName
+            __typename
+          }
+          __typename
+        }
+        __typename
+      }
+    `);
     const expectedQueryStr = print(expectedQuery);
 
     assert.equal(expectedQueryStr, modifiedQueryStr);