[Umbrella] v3 data fetching follow-through and Gameplan migration

[netchampfaris]

Post-v1 follow-through on v3 data fetching: full Gameplan migration off v1
resources, ergonomic additions surfaced during migration, Frappe v15 backport,
and the eventual v2 deprecation decision.

v3 itself ships in v1.0 via PR #610 with a frozen public import surface.
This umbrella tracks the work that intentionally did not block 1.0.

In scope

Gameplan migration

• frontend/src no longer uses:
  • resources: {}, $resources, $getResource
  • createResource, createListResource, createDocumentResource
• v1 resource usage removed from active app codepaths
• Migration findings folded back into v3 API improvements

v3 ergonomics (additive within frozen surface contract)

• .submit, .cancel, and similar parity gaps surfaced during migration
• DocType Meta composable (DocType Meta composable #260)
• Cancel ongoing fetch requests in handles (Cancel ongoing fetch requests in resources when component is unmounted #26 — re-scope for v3, not legacy resources)
• Additional cache adapter implementations if needed

Backend / framework

• Frappe v15 /api/v2/* backport — until this lands, v3 stays v16+ only
• Session and user utilities (Session and user utilities #441)
• First-class socket.io utilities
• Broader internal migration of frappe-ui/frappe/* to v3

v2 deprecation decision

• Re-evaluate after Gameplan migration completes and v15 backport status is known
• If kept supported, document long-term coexistence; if deprecated, define removal target (likely v2.0)

Acceptance

• Gameplan fully migrated off v1 resources
• v3 ergonomic gaps from migration are closed
• v15 backport status resolved (landed, or explicitly punted)
• v2's fate decided and documented
• Any additions to v3 honor the v1.x frozen-surface contract (no breaking changes; deprecation cycles only)

References

• v1 plan: v1-release/plan.md — workstreams §4 (carve-out) and §5
• v3 spec: frappe/client/spec/{api,core,vue}.md (in PR frappe/client — data-fetching v3 #610)
• v3 frozen surface contract: see v1-release/plan.md Data API strategy section

Raw

1. Ability to append/remove/modify a child row in a document

2. Ability to fetch a "publicly accessible" document via data fetching utility.

 // for some documents that have `public=1`, allow get doc without permission check
doc = InsightsQuery.get(<>)
// same with a few methods that should be callable without auth/perms
doc.execute()

3. First-class doc editing API
   doc.isDirty(), doc.discard()

let todo = ToDo.getDoc(() => props.id)
todo.description = 'asdf'
todo.save.call()

4. doc.submit.call(), doc.cancel.call()

5. staleness check api
   if a fetched document is changed at the server side, set doc.isStale = true

6. If multiple doc.setValue.call() calls, there can be two modes: one is queue all setValue calls one after the other, or debounce.

7. Attempt todo.setValue() (without the .call) with typescript support

8. Task.getMeta()