GeezerVison

Builds on #67 (getMergedData, generated, unique, the shared fetches), so this PR targets its branch. Once #67 is merged, it needs a rebase onto main.

New

Hooks

• check works like a CHECK constraint across fields, e.g. startDate <= endDate. The fields are read with getMergedData, so a patch of only endDate is checked against the stored startDate, which a validator of data can't do. Nothing is checked for a patch that touches none of the fields, or for items whose fields keep their values. test runs per item and may be async; error replaces the BadRequest.
• restrictQuery({ fields }) limits the fields external callers may filter, sort and select by, and the operators they may use on each. It covers $and/$or/$nor, $sort, $select and nested paths, and the id field is always allowed. Without it, a client can filter by { password: { $regex: '^a' } }. Internal calls are not restricted.
• skipUnchanged drops the fields of a patch that keep their stored value (for every item of a multi patch). If nothing changes, the write is skipped: the result is the stored items, with the call's $select, and no patched event is sent. ignore: ['updatedAt'] keeps timestamps from counting as a change.
• counterCache keeps a count on the parent item, e.g. posts.commentCount, across create, remove, and patch/update that moves items. It counts every touched parent again with count (where can narrow the count) instead of $inc, which isn't portable. Parents with an equal count share a write.
• denormalize copies fields from a related item and keeps them in sync. It returns two hooks:
  • target is a generated hook that fills e.g. posts.authorName from users.name, with one query per call.
  • source copies changed fields to the target items with one patchMany per changed source item. These patches go through the target's hooks and send events. The two hooks share a mark in params, so target lets the patches of source through.

Utils

• getChanges(before, after, fields?) returns the fields that differ, as { [path]: { before, after } }, compared with isDeepEqual.

Options

• select: false on getMergedData, generated, unique and check fetches whole items instead of just the needed fields, so stash, trigger and later hooks of the call reuse the fetch.

Changed

• preventChanges now compares with the stored item:
  • On update it always compares. A changed field gets its stored value back (or the hook throws with error). Before, it deleted the field, because update replaces the whole item, and with error it always threw.
  • On patch, the comparison is opt-in with compare: true. A nested field that changes gets its stored value back instead of being removed, since its parent replaces the stored one as a whole.

Internal

• call-fetches.ts: fetchStored (the items before the call, narrow or whole, shared per call) and resultWith (the result, refetched only if the call's $select drops a needed field). Used by getMergedData, preventChanges, skipUnchanged, counterCache and denormalize.

Review notes

• preventChanges on update is a behavior change, see above.
• preventChanges without compare still turns { role: { type } } into { role: {} } when role.type is protected, which wipes the stored role.type. This is existing behavior with an existing test, so I left it unchanged; it's worth a follow-up.
• counterCache and denormalize write after the call. Without a transaction in params, those writes are not atomic with the call.

Testing

pnpm test (lint, typecheck, coverage) passes: 173 test files, 2091 tests, coverage 97.8%. pnpm build passes, and the new exports load from dist.

🤖 Generated with Claude Code