fix: canonicalize hidden system metadata

src/hooks/frontmatterOps.systemMetadata.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest'
+import type { VaultEntry } from '../types'
+import { contentToEntryPatch, frontmatterToEntryPatch } from './frontmatterOps'
+
+describe('frontmatterOps system metadata', () => {
+  it.each([
+    ['_icon', 'rocket', { icon: 'rocket' }],
+    ['icon', 'rocket', { icon: 'rocket' }],
+    ['_order', 4, { order: 4 }],
+    ['order', 4, { order: 4 }],
+    ['_sort', 'title:asc', { sort: 'title:asc' }],
+    ['sort', 'title:asc', { sort: 'title:asc' }],
+    ['_sidebar_label', 'Projects', { sidebarLabel: 'Projects' }],
+    ['sidebar label', 'Projects', { sidebarLabel: 'Projects' }],
+  ] as [string, unknown, Partial<VaultEntry>][])('maps %s to the expected entry field', (key, value, expected) => {
+    expect(frontmatterToEntryPatch('update', key, value as never).patch).toEqual(expected)
+  })
+
+  it('maps canonical delete keys for system metadata', () => {
+    expect(frontmatterToEntryPatch('delete', '_icon').patch).toEqual({ icon: null })
+    expect(frontmatterToEntryPatch('delete', '_sidebar_label').patch).toEqual({ sidebarLabel: null })
+    expect(frontmatterToEntryPatch('delete', '_order').patch).toEqual({ order: null })
+    expect(frontmatterToEntryPatch('delete', '_sort').patch).toEqual({ sort: null })
+  })
+
+  it('keeps canonical system metadata out of custom properties', () => {
+    const patch = contentToEntryPatch(
+      '---\ntype: Type\n_icon: rocket\n_order: 4\n_sidebar_label: Projects\n_sort: title:asc\n_internal: secret\nOwner: Luca\n---\n# Project\n',
+    )
+
+    expect(patch).toEqual({
+      isA: 'Type',
+      icon: 'rocket',
+      order: 4,
+      sidebarLabel: 'Projects',
+      sort: 'title:asc',
+      properties: { Owner: 'Luca' },
+    })
+  })
+})