angular/angular

Forms should throw error if two or more NgModels appear in form with the same name

Open

#13993 opened on Jan 18, 2017

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 (20 comments) (11 reactions) (0 assignees)TypeScript (100,110 stars) (27,214 forks)batch import
area: formsfeaturefeature: under considerationfreq1: lowgood first issuestate: has PR

Description

[ ] bug report => search github for a similar issue or PR before submitting [x] feature request [ ] support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

Currently there is no error or warning if two form controls have the same name:

<input name="entireStateCoverage" type="checkbox" [(ngModel)]="item.entireStateCoverage">
<input name="entireStateCoverage" type="checkbox" [(ngModel)]="item.active">

Expected behavior

Forms should throw error if duplicate names are detected.

What is the motivation / use case for changing the behavior?

This leads to unpredictable results (value overwrites) which are difficult to find.

  • Angular version: 2.4.3

  • Browser: [all]

  • Language: [all]

Contributor guide

Tech stack
typescriptangular
Domain
frontend
Issue type
feature
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
None
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Investigate the Angular forms module to understand how NgModel directives register their names. Look for existing validation mechanisms in the AbstractControl class or the ControlContainer. Consider adding a check when two NgModels with the same name are registered and throw an error. Relevant files might include forms/directives/ng model.ts and forms/validators.ts. Also review the issue comments (20 comments) for any proposed solutions or design discussions.