Strip duplicate fragments from AST

While duplicate fragments will result in “warnings”, generating a document with duplicate fragments results in an invalid GraphQL document. This was recently introduced when fragment interpolation became the defacto way to insert fragments.

See upstream issue [here](apollographql#27). This is not intended to go upstream (yet).

index.js

@@ -26,8 +26,8 @@ function resetCaches() {
 // check all fragment definitions, checking for name->source uniqueness
 var printFragmentWarnings = true;
 function checkFragments(ast) {
-  for (var i = 0; i < ast.definitions.length; i++) {
-    var fragmentDefinition = ast.definitions[i];
+  const astFragmentMap = {};
+  ast.definitions = ast.definitions.filter(fragmentDefinition => {
     if (fragmentDefinition.kind === 'FragmentDefinition') {
       var fragmentName = fragmentDefinition.name.value;
       var sourceKey = cacheKeyFromLoc(fragmentDefinition.loc);
@@ -51,7 +51,14 @@ function checkFragments(ast) {
         fragmentSourceMap[fragmentName][sourceKey] = true;
       }
     }
-  }
+
+    if (!astFragmentMap[sourceKey]) {
+      astFragmentMap[sourceKey] = true;
+      return true;
+    } else {
+      return false;
+    }
+  });
 }
 
 function disableFragmentWarnings() {

test.js

@@ -282,6 +282,20 @@ const assert = require('chai').assert;
       });
     });
 
+    describe('fragment de-duplication', () => {
+      beforeEach(() => {
+        gqlRequire.resetCaches();
+      });
+
+      it('strips duplicate fragments from the document', () => {
+        const frag1 = gql`fragment TestDuplicate on Bar { field }`;
+        const query1 = gql`{ bar { fieldOne ...TestDuplicate } } ${frag1} ${frag1}`;
+
+        assert.equal(query1.definitions.length, 2);
+        assert.equal(query1.definitions[1].kind, 'FragmentDefinition')
+      });
+    });
+
     // How to make this work?
     // it.only('can reference a fragment passed as a document via shorthand', () => {
     //   const ast = gql`