Add ast toString returning query string

src/index.js

@@ -1,6 +1,8 @@
 var parser = require('graphql/language/parser');
+var printer = require('graphql/language/printer');
 
 var parse = parser.parse;
+var print = printer.print;
 
 // Strip insignificant whitespace
 // Note that this could do a lot more, such as reorder fields etc.
@@ -135,6 +137,7 @@ function parseDocument(doc) {
   // existing fragments of the same name
   parsed = processFragments(parsed);
   parsed = stripLoc(parsed, false);
+  parsed.toString = function() { return print(this); };
   docCache[cacheKey] = parsed;
 
   return parsed;

test/graphql.js

@@ -2,6 +2,7 @@ const gqlRequire = require('../src');
 const gqlDefault = require('../src').default;
 const loader = require('../loader');
 const assert = require('chai').assert;
+const print = require('graphql/language/printer').print;
 
 [gqlRequire, gqlDefault].forEach((gql, i) => {
   describe(`gql ${i}`, () => {
@@ -438,6 +439,22 @@ const assert = require('chai').assert;
       });
     });
 
+    it('returned ast toString returns query string', () => {
+      const query = `{ user(id: 5) { firstName lastName } }`;
+      const doc = gql(query);
+
+      assert.equal(doc.toString(), print(doc));
+    });
+
+    it('returned ast toString returns updated query string after ast mutation', () => {
+      const query = `{ user(id: 5) { firstName lastName } }`;
+      const doc = gql(query);
+
+      assert.equal(doc.toString().includes('user'), true);
+      doc.definitions[0].selectionSet.selections[0].name.value = 'employee';
+      assert.equal(doc.toString().includes('employee'), true);
+    });
+
     // How to make this work?
     // it.only('can reference a fragment passed as a document via shorthand', () => {
     //   const ast = gql`