Add support for sparse javascript objects

For objects, silently drop undefined fields. For arrays, convert undefined entries to null. (Supporting true undefined values in arrays would require protocol changes, so null seems good enough for now)

Related to neo4j#91

Author: kpdecker

src/v1/internal/packstream.js

@@ -96,17 +96,27 @@ class Packer {
     } else if (x instanceof Array) {
       this.packListHeader(x.length);
       for(let i = 0; i < x.length; i++) {
-        this.pack(x[i]);
+        this.pack(x[i] === undefined ? null : x[i]);
       }
     } else if (x instanceof Structure) {
       this.packStruct( x.signature, x.fields );
     } else if (typeof(x) == "object") {
       let keys = Object.keys(x);
-      this.packMapHeader(keys.length);
+
+      let count = 0;
+      for(let i = 0; i < keys.length; i++) {
+        if (x[keys[i]] !== undefined) {
+          count++;
+        }
+      }
+
+      this.packMapHeader(count);
       for(let i = 0; i < keys.length; i++) {
         let key = keys[i];
-        this.packString(key);
-        this.pack(x[key]);
+        if (x[key] !== undefined) {
+          this.packString(key);
+          this.pack(x[key]);
+        }
       }
     } else {
       throw newError("Cannot pack this value: " + x);

test/v1/types.test.js

@@ -49,6 +49,7 @@ describe('string values', function() {
 
 describe('list values', function() {
   it('should support empty lists ',   testVal( [] ) );
+  it('should support sparse lists ',   testVal( [ undefined, 4 ], [ null, 4 ] ) );
   it('should support float lists ',   testVal( [ 1,2,3 ] ) );
   it('should support boolean lists ', testVal( [ true, false ] ) );
   it('should support string lists ',  testVal( [ "", "hello!" ] ) );
@@ -59,6 +60,7 @@ describe('list values', function() {
 describe('map values', function() {
   it('should support empty maps ', testVal( {} ) );
   it('should support basic maps ', testVal( {a:1, b:{}, c:[], d:{e:1}} ) );
+  it('should support sparse maps ', testVal( {foo: undefined, bar: null}, {bar: null} ) );
 });
 
 describe('node values', function() {
@@ -131,14 +133,14 @@ describe('path values', function() {
   });
 });
 
-function testVal( val ) {
+function testVal( val, expected ) {
   return function( done ) {
     var driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "neo4j"));
     var session = driver.session();
 
     session.run("RETURN {val} as v", {val: val})
       .then( function( result ) {
-        expect( result.records[0].get('v') ).toEqual( val );
+        expect( result.records[0].get('v') ).toEqual( expected || val );
         driver.close();
         done();
       }).catch(function(err) { console.log(err); });