Fix the Properties panel rejecting Obsidian-style empty tags: /…

.changeset/obsidian-empty-tags-frontmatter.md

@@ -0,0 +1,6 @@
+---
+"@inkeep/open-knowledge-core": patch
+"@inkeep/open-knowledge": patch
+---
+
+Fix the Properties panel rejecting Obsidian-style empty `tags:` / `aliases:` frontmatter. Files that use Obsidian's default "no tags" shape (an empty `tags:` list whose only item is a blank `- `, or a bare `tags:` with no value) parse to YAML `null`, which the read schema previously rejected for the whole frontmatter block — so the panel showed nothing (or an error banner) and refused every edit, even to the file's other valid properties. The read path now coerces these empty shapes to empty values (`tags:\n- ` reads as an empty list, a bare `tags:` as empty text), so the panel reads and edits these files normally. Files are not rewritten on disk until you actually edit a property.

packages/core/src/frontmatter/schema.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, test } from 'bun:test';
 import {
   FRONTMATTER_TYPES,
+  FrontmatterMapSchema,
   frontmatterValuesEqual,
   inferType,
   isFrontmatterValueEmpty,
@@ -122,3 +123,37 @@ describe('frontmatterValuesEqual', () => {
     expect(frontmatterValuesEqual({ a: 1, b: 2 }, { a: 1, c: 2 })).toBe(false);
   });
 });
+
+describe('FrontmatterMapSchema — Obsidian null coercion', () => {
+  test('drops null sequence elements ([null] → [])', () => {
+    const result = FrontmatterMapSchema.safeParse({ tags: [null] });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data).toEqual({ tags: [] });
+  });
+
+  test('drops null elements but keeps real items in a mixed sequence', () => {
+    const result = FrontmatterMapSchema.safeParse({ aliases: ['Real', null, 'Also'] });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data).toEqual({ aliases: ['Real', 'Also'] });
+  });
+
+  test('coerces a bare-key null scalar to an empty string (key stays visible)', () => {
+    const result = FrontmatterMapSchema.safeParse({ tags: null, author: 'Alice' });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data).toEqual({ tags: '', author: 'Alice' });
+  });
+
+  test('coerces null nested inside a mapping subtree', () => {
+    const result = FrontmatterMapSchema.safeParse({ metadata: { version: null, name: 'x' } });
+    expect(result.success).toBe(true);
+    if (result.success) expect(result.data).toEqual({ metadata: { version: '', name: 'x' } });
+  });
+
+  test('leaves null-free maps untouched (no behavior change for valid input)', () => {
+    const input = { title: 'Hello', tags: ['a', 'b'], meta: { n: 1 } };
+    const result = FrontmatterMapSchema.safeParse(input);
+    expect(result.success).toBe(true);
+    if (result.success)
+      expect(result.data).toEqual({ title: 'Hello', tags: ['a', 'b'], meta: { n: 1 } });
+  });
+});

packages/core/src/frontmatter/schema.ts

@@ -48,7 +48,29 @@ export function inferType(value: FrontmatterValue): FrontmatterType {
   return 'text';
 }
 
-export const FrontmatterMapSchema = z.record(z.string(), FrontmatterValueSchema);
+function coerceNullFrontmatter(value: unknown): unknown {
+  if (Array.isArray(value)) {
+    const out: unknown[] = [];
+    for (const element of value) {
+      if (element === null) continue;
+      out.push(coerceNullFrontmatter(element));
+    }
+    return out;
+  }
+  if (value !== null && typeof value === 'object') {
+    const out: Record<string, unknown> = {};
+    for (const [key, child] of Object.entries(value as Record<string, unknown>)) {
+      out[key] = child === null ? '' : coerceNullFrontmatter(child);
+    }
+    return out;
+  }
+  return value;
+}
+
+export const FrontmatterMapSchema = z.preprocess(
+  coerceNullFrontmatter,
+  z.record(z.string(), FrontmatterValueSchema),
+);
 export type FrontmatterMap = Record<string, FrontmatterValue>;
 
 export const FrontmatterPatchSchema = z.record(

packages/core/src/frontmatter/tags.test.ts

@@ -75,6 +75,14 @@ describe('extractFrontmatterTags', () => {
     expect(extractFrontmatterTags('tags: null\n')).toEqual([]);
   });
 
+  test("returns empty for Obsidian's empty-list shape (`tags:\\n- `)", () => {
+    expect(extractFrontmatterTags('tags:\n- \n')).toEqual([]);
+  });
+
+  test('drops a null entry but keeps real tags in a mixed block sequence', () => {
+    expect(extractFrontmatterTags('tags:\n  - real\n  - \n  - also\n')).toEqual(['real', 'also']);
+  });
+
   test('drops object array elements rather than stringifying them', () => {
     const yaml = 'tags:\n  - valid\n  - {nested: "object"}\n  - alsoValid\n';
     expect(extractFrontmatterTags(yaml)).toEqual(['valid', 'alsoValid']);

packages/core/src/frontmatter/yaml-codec.test.ts

@@ -60,6 +60,14 @@ describe('parseFrontmatterYaml', () => {
     expect(parseFrontmatterYaml('"just a string"').map).toBeNull();
   });
 
+  test("coerces Obsidian's empty-list / bare-key null shapes instead of rejecting the map", () => {
+    expect(parseFrontmatterYaml('tags:\n- \n').map).toEqual({ tags: [] });
+    expect(parseFrontmatterYaml('tags:\n').map).toEqual({ tags: '' });
+    const mixed = parseFrontmatterYaml('plugin-id: dataview\ntags:\n- \npublish: true\n');
+    expect(mixed.parseError).toBeUndefined();
+    expect(mixed.map).toEqual({ 'plugin-id': 'dataview', tags: [], publish: true });
+  });
+
   test('parses nested objects into a populated map with no parseError', () => {
     const yaml = 'name: skill\nmetadata:\n  version: 1.0.0\n  author: Inkeep\n';
     const { map, parseError } = parseFrontmatterYaml(yaml);

packages/server/src/api-agent-frontmatter.test.ts

@@ -698,6 +698,45 @@ describe('POST /api/agent-write-md (write_document) — malformed-FM refusal (PR
     }
   });
 
+  test("Obsidian's empty `tags:` / `aliases:` null shapes write through (200), not refused at the gate", async () => {
+    const { contentDir, hocuspocus, sessionManager, cleanup } = setup();
+    try {
+      const session = await sessionManager.getSession('test-doc');
+
+      const obsidianShape = [
+        '---',
+        'plugin-id: dataview',
+        'tags:',
+        '- ',
+        'aliases:',
+        '- ',
+        'publish: true',
+        '---',
+        '',
+        '# Body',
+        '',
+      ].join('\n');
+
+      const response = await callApi(
+        hocuspocus,
+        sessionManager,
+        contentDir,
+        '/api/agent-write-md',
+        { docName: 'test-doc', markdown: obsidianShape, position: 'replace' },
+      );
+
+      expect(response.status).toBe(200);
+      expect(fmMap(session.dc.document)).toEqual({
+        'plugin-id': 'dataview',
+        tags: [],
+        aliases: [],
+        publish: true,
+      });
+    } finally {
+      await cleanup();
+    }
+  });
+
   test('append AND prepend skip the gate even when the existing FM is already malformed', async () => {
     const { contentDir, hocuspocus, sessionManager, cleanup } = setup();
     try {