Restore val:null in decorate with toJSON hack

src/common/coding/decodeTree.js

@@ -1,4 +1,5 @@
 import { isBranch, isLink, isPrefix, isRange } from '../node/index.js';
+import { NULL_VAL } from '../object.js';
 import { keyAfter } from '../ops/index.js';
 import { clone, cmp, isDef, isEmpty, isMaxKey, isMinKey } from '../util.js';
 import { decode as decodeArgs, splitArgs } from './args.js';
@@ -90,7 +91,7 @@ function decode(nodes = [], { isGraph } = {}) {
           delete item.$val;
 
           if ($val === null) {
-            $val = { $val };
+            $val = NULL_VAL;
           } else if (typeof $val === 'object') {
             $val = clone($val);
             Object.defineProperty($val, '$val', { value: true });

src/common/coding/decorate.js

@@ -1,4 +1,5 @@
 import { findFirst, isRange } from '../node/index.js';
+import { NULL_VAL } from '../object.js';
 import { IS_VAL, getNodeValue, unwrap } from '../ops/index.js';
 import {
   MIN_KEY,
@@ -26,7 +27,7 @@ const PRE = Symbol();
 export default function decorate(rootGraph, rootQuery) {
   // console.log('Decorating', rootGraph, rootQuery);
   function construct(plumGraph, query) {
-    if (plumGraph === null) return null;
+    if (plumGraph === null || plumGraph === NULL_VAL) return plumGraph;
     if (!isDef(plumGraph)) plumGraph = [];
     if (query.$key) query = [query];
 
@@ -95,15 +96,15 @@ export default function decorate(rootGraph, rootQuery) {
     } else if (query) {
       if (Array.isArray(plumGraph) && !plumGraph.length) {
         graph = undefined;
-      } else if (typeof plumGraph !== 'object' || !plumGraph) {
+      } else if (typeof plumGraph !== 'object') {
         graph = plumGraph;
       } else if (plumGraph[IS_VAL]) {
         graph = Array.isArray(plumGraph)
           ? plumGraph.slice(0)
           : { ...plumGraph };
         graph.$val = true;
       } else if (Array.isArray(plumGraph)) {
-        graph = deValNull(decodeGraph(plumGraph));
+        graph = decodeGraph(plumGraph);
       } else {
         throw Error('decorate.unexpected_graph');
       }
@@ -180,16 +181,6 @@ export default function decorate(rootGraph, rootQuery) {
   return result;
 }
 
-// Replace $val: null produced by
-function deValNull(graph) {
-  if (typeof graph !== 'object' || !graph) return graph;
-  if ('$val' in graph && graph.$val !== true) return graph.$val;
-
-  // Important: update graph in-place to avoid losing non-enumerable props.
-  for (const prop in graph) graph[prop] = deValNull(graph[prop]);
-  return graph;
-}
-
 function addPageMeta(graph, args) {
   if (args.$all) {
     Object.assign(graph, { $page: args, $prev: null, $next: null });

src/common/coding/test/decorate.test.js

@@ -1,5 +1,6 @@
 import { page } from '@graffy/testing';
 import { e } from '@graffy/testing/encoder.js';
+import { NULL_VAL } from '../../object.js';
 import { keyAfter as aft, keyBefore as bef } from '../../ops/step.js';
 import { MAX_KEY, MIN_KEY } from '../../util.js';
 import { decode } from '../base64.js';
@@ -174,13 +175,13 @@ describe('val_null', () => {
       ],
       { foo: 1 },
     );
-    expect(result).toEqual({ foo: { bar: null } });
+    expect(result).toEqual({ foo: { bar: NULL_VAL } });
   });
 
   test('explicit', () => {
     const result = decorate([{ key: e.foo, version: 0, value: null }], {
       foo: 1,
     });
-    expect(result).toEqual({ foo: null });
+    expect(result).toEqual({ foo: NULL_VAL });
   });
 });

src/common/coding/test/roundTrip.test.js

@@ -1,3 +1,4 @@
+import { NULL_VAL } from '../../object.js';
 import {
   decodeGraph,
   decodeQuery,
@@ -58,7 +59,7 @@ describe('graph', () => {
   });
 
   test('val_null', () => {
-    roundTrip({ foo: { $val: null } });
+    roundTrip({ foo: { $val: null } }, { foo: NULL_VAL });
   });
 
   test('val_scalar', () => {

src/common/object.js

@@ -2,6 +2,10 @@ import isEqual from 'lodash/isEqual.js';
 import { splitArgs } from './coding/index.js';
 import { isEmpty } from './util.js';
 
+export const NULL_VAL = {};
+Object.defineProperty(NULL_VAL, '$val', { value: null });
+Object.defineProperty(NULL_VAL, 'toJSON', { value: () => null });
+
 export function mergeObject(base, change) {
   if (
     typeof change !== 'object' ||

src/common/ops/path.js

@@ -1,4 +1,5 @@
 import { findFirst, isBranch, isRange } from '../node/index.js';
+import { NULL_VAL } from '../object.js';
 import { cmp } from '../util.js';
 
 export const IS_VAL = Symbol('IS_VAL');
@@ -53,7 +54,8 @@ export function unwrap(tree, path) {
 
 export function getNodeValue(node) {
   if (node.children) return node.children;
-  if (node.value && typeof node.value === 'object') {
+  if (node.value === null) return NULL_VAL;
+  if (typeof node.value === 'object') {
     node.value[IS_VAL] = true;
   }
   return node.value;