## Context
Follow-up to #22362, which made `isNullable` manifest changes actually
apply (including a nullable → non-nullable backfill). This models the
`isNullable` / `defaultValue` relationship directly in the
`FieldManifest` type.
## Rule
- A **non-nullable** field (`isNullable: false`) must declare a
`defaultValue`, so the column always has a value to fall back on (e.g.
for the backfill on the nullable → non-nullable transition).
- A **nullable** or **unspecified** field may omit `defaultValue`.
## Changes
- Split `RegularFieldManifest` into a base shape plus a discriminated
nullability union. The union keeps `isNullable` free once a
`defaultValue` is supplied, so helpers that always provide one can still
pass a dynamic `boolean` `isNullable`.
- `defaultValue` keeps its rich per-type `FieldMetadataDefaultValue<T>`
(POSITION → number, ACTOR → composite) rather than a bare `string`.
- `RelationFieldManifest` is rebased on the shared base and keeps
`isNullable` / `defaultValue` optional, since relation join columns are
always nullable by design.
- Narrowed `buildEstimateFieldManifest` in the manifest-update
integration test to satisfy the stricter type.
## Verification
Environment couldn't install the monorepo deps (registry connections
aborting), so `nx typecheck` wasn't run here. Validated the union
structure with standalone `tsc` synthetic tests mirroring every
construction pattern in the codebase:
- ✅ nullable/no-default, no-`isNullable`, non-nullable with
string/number/composite defaults, dynamic-boolean-with-default, and the
`DistributiveOmit` path into `ObjectFieldManifest`
- ✅ non-nullable **without** a default is correctly rejected with a
clear "defaultValue is missing but required" error
Recommend a full `nx typecheck twenty-shared twenty-sdk twenty-server`
in CI to confirm against full project resolution.
https://claude.ai/code/session_01VnbrgBB3kNGP876qaKPYDL
---
_Generated by [Claude
Code](https://claude.ai/code/session_01VnbrgBB3kNGP876qaKPYDL)_
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Thomas des Francs
