Class constraints: nested JSON Schema for json and array values

CHANGELOG.md

@@ -7,6 +7,7 @@ See [STATUS.md](server/STATUS.md) to learn more about which features will remain
 
 ## UNRELEASED
 
+- Class constraints: a property's entry in `constraints` can describe nested JSON values with `type` (including `["string", "null"]`), `const`, `properties`, `required`, `additionalProperties`, `items` and `anyOf`, up to 16 levels deep. Every keyword works at every level and errors name the failing value by JSON pointer (`... breaks maximum on class patch at /pad/tune: ...`). JSON Schema import keeps nested schemas, nullable types and `anyOf` below a property as `json` plus constraints instead of refusing them, and export writes them back (`docs/src/schema/classes.md`, `json-schema.md`). Older nodes reject commits that put the new keywords in a class, and skip every constraint of such a class (flat ones included) when it reaches them by sync.
 - Loro documents: strings that start with `[`, `{`, `atomic:`, `did:ad:` or `http(s)://` are tagged as `string` in the `datatypes` map so they are no longer read back as nested resources or URLs, and JSON `null` is kept inside nested maps and lists.
 
 ## [v0.41.0-beta.8] - 2026-10-10

browser/data-browser/src/chunks/FormBuilder/useFormFieldPropertySync.ts

@@ -2,10 +2,10 @@ import {
   canonicalizeScheme,
   core,
   forms,
-  parseConstraints,
   Resource,
   setClassConstraint,
   Store,
+  type ConstraintPatch,
   useResource,
   useStore,
 } from '@tomic/react';
@@ -105,13 +105,20 @@ async function moveClassConstraint(
     return;
   }
 
-  const entry = parseConstraints(raw).get(canonicalizeScheme(from));
+  // Move the stored JSON, not a parsed constraint: nested schemas and
+  // patterns have to arrive exactly as they were written.
+  const map: unknown = typeof raw === 'string' ? JSON.parse(raw) : raw;
+  const key = canonicalizeScheme(from);
+  const entry =
+    typeof map === 'object' && map !== null
+      ? Object.entries(map).find(([k]) => canonicalizeScheme(k) === key)?.[1]
+      : undefined;
 
-  if (!entry) {
+  if (typeof entry !== 'object' || entry === null || Array.isArray(entry)) {
     return;
   }
 
-  await setClassConstraint(dataClass, to, entry);
+  await setClassConstraint(dataClass, to, entry as ConstraintPatch);
   await setClassConstraint(dataClass, from, undefined);
 }
 

browser/lib/src/class-constraints.test.ts

@@ -13,6 +13,10 @@ interface FixtureCase {
   value: unknown;
   valid: boolean;
   rule?: string;
+  /** JSON pointer of the failing value, when the case pins it. */
+  path?: string;
+  /** The constraint itself must be refused by the parser. */
+  rejected?: boolean;
 }
 
 const cases = JSON.parse(
@@ -31,6 +35,12 @@ describe('class constraints fixture', () => {
   });
 
   it.each(cases.map((c, i) => [i, c] as const))('case %i', (_i, c) => {
+    if (c.rejected) {
+      expect(() => parseConstraint(c.constraint)).toThrow();
+
+      return;
+    }
+
     const constraint = parseConstraint(c.constraint);
 
     if (c.valid) {
@@ -45,6 +55,9 @@ describe('class constraints fixture', () => {
     } catch (e) {
       expect(e).toBeInstanceOf(ConstraintError);
       expect((e as ConstraintError).keyword).toBe(c.rule);
+
+      if (c.path !== undefined)
+        expect((e as ConstraintError).path).toBe(c.path);
     }
   });
 });
@@ -109,6 +122,41 @@ describe('checkResourceConstraints', () => {
     );
   });
 
+  it('names the nested path in the message', () => {
+    const nested = new Map(store);
+
+    nested.set(classSubject, {
+      'https://atomicdata.dev/properties/shortname': 'task',
+      'https://atomicdata.dev/properties/constraints': {
+        [nameProp]: {
+          type: 'object',
+          properties: { tune: { type: 'number', maximum: 24 } },
+        },
+      },
+    });
+
+    const getNested = (subject: string) => {
+      const props = nested.get(subject);
+
+      return (
+        props && { subject, getClasses: () => [], get: (p: string) => props[p] }
+      );
+    };
+
+    const withValue = (value: unknown) => ({
+      subject: 'https://example.com/t1',
+      getClasses: () => [classSubject],
+      get: (p: string) => (p === nameProp ? value : undefined),
+    });
+
+    expect(() =>
+      checkResourceConstraints(withValue({ tune: 24 }), getNested),
+    ).not.toThrow();
+    expect(() =>
+      checkResourceConstraints(withValue({ tune: 25 }), getNested),
+    ).toThrow(/^Value for name breaks maximum on class task at \/tune: /);
+  });
+
   it('skips classes that are not loaded', () => {
     expect(() =>
       checkResourceConstraints(