share/sharedb

Projection's nested fields aren't being updated when subscribing to a query

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#365 opened on Apr 21, 2020

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 (1 comment) (0 reactions) (0 assignees)JavaScript (5,791 stars) (449 forks)batch import
enhancementhelp wanted

Description

Created a projection as follows:

  backend.addProjection 'gameInfos', 'games',
    id: true
    testGame: true
    host: true
    classIds: true
    createdAt: true    
    mode: true
    'scenario.name': true
    'scenario.labels.publish': true
    'scenario.labels.unpublish': true
    'scenario.scenarioName': true
    'scenario.playedAt': true
    'scenario.gameCategory': true
    'scenario.gameType': true
    'scenario.password': true
    'scenario.roles': true

Subscribed to a regular query:

   $games = @model.query 'gameInfos', someQuery
   @model.subscribe $games, =>
       @model.ref '_page.games', $games
       @page.render ...

All first-level nested fields, e.g. mode, host are being reactively updated. But the specified nested fields, e.g. scenario.name are not. It will work fine if I pass just scenario: true into addProjection, i.e. all nested fields under scenario object will be updated reactively, but what if I only want a subset of the nested fields.

Contributor guide

Tech stack
javascriptnodejs
Domain
backenddatabaseapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understanding of ShareDB projectionsFamiliarity with Node.jsKnowledge of Operational Transformation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the projection handling in ShareDB's client or server code, specifically how nested fields are merged during updates. Look at the subscription logic and the diff/op processing for projections. The issue describes that nested fields specified with dot notation are not updating reactively, while passing the parent object works. This suggests a bug in the field inclusion logic for nested paths. The fix likely involves correcting the projection resolution or the application of updates to nested fields. No linked PRs or assignees; consider examining the 'ot' or 'projection' modules in the repository.