fix: decompose should preserve ordering of query results (#531)

* Add failing test

* Fix: Decomposed results are not ordered correctly

The issue was caused by a behavior of Object.keys() which sorts integer keys numerically. This fix ensures that the keys are strictly treated as strings by simply prefixing a non-numeric character onto each id used as a key in the decompose mapping.

* Fix test broken by previous fix

lib/util/decompose.js

@@ -44,22 +44,27 @@ exports = module.exports = function (schema, data) {
     return (function build (obj, objSchema) {
       const id = row[objSchema.pk];
 
+      // Use a string id instead of the (potentially numerical) row id as keys
+      // in the mapping. This prevents Object.keys from reordering the
+      // mapping in the "transform" step.
+      const strid = '_' + id;
+
       if (id === null) {
         // null id means this entity doesn't exist (eg outer join)
         return undefined;
-      } else if (!obj.hasOwnProperty(id)) {
+      } else if (!obj.hasOwnProperty(strid)) {
         // this entity is new
-        obj[id] = {};
+        obj[strid] = {};
       }
 
       let mapper;
 
       if (_.isArray(objSchema.columns)) {
         // columns is just a list of field names
-        mapper = val => obj[id][val] = row[val];
+        mapper = val => obj[strid][val] = row[val];
       } else {
         // the columns object maps field names in the row to object key names
-        mapper = (val, key) => obj[id][val] = row[key];
+        mapper = (val, key) => obj[strid][val] = row[key];
       }
 
       _.map(objSchema.columns, mapper);
@@ -68,13 +73,13 @@ exports = module.exports = function (schema, data) {
         switch (c) {
           case 'pk': case 'columns': case 'array': break;
           default: {
-            const descendant = build(obj[id][c] || {}, objSchema[c]);
+            const descendant = build(obj[strid][c] || {}, objSchema[c]);
 
             if (descendant) {
-              obj[id][c] = descendant;
+              obj[strid][c] = descendant;
             } else if (objSchema[c].array) {
               // we always want an array if there could be multiple descendants
-              obj[id][c] = [];
+              obj[strid][c] = [];
             }
 
             break;

test/queryable/decomposition.js

@@ -61,10 +61,6 @@ describe('decomposing results', function () {
       id: 3,
       username: 'carol',
       tests: [{
-        id: 2,
-        name: 'carol\'s first test',
-        issues: []
-      }, {
         id: 3,
         name: 'carol\'s second test',
         issues: [{
@@ -73,6 +69,10 @@ describe('decomposing results', function () {
           test_id: 3,
           description: 'carol\'s issue'
         }]
+      }, {
+        id: 2,
+        name: 'carol\'s first test',
+        issues: []
       }]
     }]);
   });
@@ -122,4 +122,71 @@ describe('decomposing results', function () {
       });
     });
   });
+
+  it('preserves ordering of query results', function* () {
+    const issues = yield db.everything.find({}, {
+      decompose: {
+        pk: 'user_id',
+        columns: {
+          user_id: 'id',
+          username: 'username'
+        },
+        tests: {
+          pk: 'test_id',
+          columns: {
+            test_id: 'id',
+            name: 'name'
+          },
+          array: true,
+          issues: {
+            pk: 'id',
+            columns: {
+              id: 'id',
+              user_id: 'user_id',
+              test_id: 'test_id',
+              description: 'description'
+            },
+            array: true
+          }
+        }
+      },
+      order: 'username DESC'
+    });
+
+    assert.deepEqual(issues, [{
+      id: 3,
+      username: 'carol',
+      tests: [{
+        id: 3,
+        name: 'carol\'s second test',
+        issues: [{
+          id: 2,
+          user_id: 3,
+          test_id: 3,
+          description: 'carol\'s issue'
+        }]
+      }, {
+        id: 2,
+        name: 'carol\'s first test',
+        issues: []
+      }]
+    }, {
+      id: 2,
+      username: 'bob',
+      tests: []
+    }, {
+      id: 1,
+      username: 'alice',
+      tests: [{
+        id: 1,
+        name: 'alice\'s test',
+        issues: [{
+          id: 1,
+          user_id: 1,
+          test_id: 1,
+          description: 'alice\'s issue'
+        }]
+      }]
+    }]);
+  });
 });