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

[kemsky]

[ ] 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]

[angular-robot[bot]]

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[dylhunn]

We'd likely accept a contribution in this area, and it's good for a first-time contributor. The message would go in forms/src/directives/template_driven_errors.ts, and the check would be somewhere in forms/src/directives.

[phalgunv]

I'd like to work on this issue.

[phalgunv]

How do I build Angular source code? When I run npm install I get the below error: `PS C:\code\angular> npm install npm ERR! code ERESOLVE npm ERR! ERESOLVE unable to resolve dependency tree npm ERR! npm ERR! While resolving: angular-srcs@14.1.0-next.0 npm ERR! Found: typescript@4.7.2 npm ERR! node_modules/typescript npm ERR! typescript@"~4.7.2" from the root project npm ERR! npm ERR! Could not resolve dependency: npm ERR! peer typescript@">=4.4.2 <4.7" from @angular/compiler-cli@13.3.11 npm ERR! node_modules/@angular/compiler-cli npm ERR! peer @angular/compiler-cli@"^13.0.0 || ^13.3.0-rc.0" from @angular-devkit/build-angular@13.3.6 npm ERR! node_modules/@angular-devkit/build-angular npm ERR! npm ERR! Fix the upstream dependency conflict, or retry npm ERR! this command with --force, or --legacy-peer-deps npm ERR!

npm ERR! A complete log of this run can be found in: npm ERR! C:\Users\pvaddepa\AppData\Local\npm-cache_logs\2022-06-08T19_35_31_088Z-debug.log`

Even npm install --force errors out. I am using node 16.10.0

Please let me know what I'm missing.

[hansireit]

@phalgunv The angular project uses yarn instead of npm. So just install yarn with "sudo npm install --global yarn" and then install the packages with yarn "yarn install". I would also like to contribute to this project, do you want to work on this issue together?

[phalgunv]

@phalgunv The angular project uses yarn instead of npm. So just install yarn with "sudo npm install --global yarn" and then install the packages with yarn "yarn install". I would also like to contribute to this project, do you want to work on this issue together?

Sure. Let's team up. My twitter handle is @PhalgunV

[GrizzlyEnglish]

@phalgunv Are you still working this? If not I'd like to give it a shot. Thanks!

[dylhunn]

@GrizzlyEnglish @phalgunv If one of you ends up implementing this, here is a code example of how to throw an Angular RuntimeError: Link to example.

As in the example, you should add a new RuntimeError enum value for the new error type.

[dylhunn]

Also @phalgunv I'm sorry I didn't see your request for setup help above. Long story short, it's much easier to get the build working on MacOS or Linux. I'd encourage you to dual-boot Linux (or possibly use WSL) to build Angular itself. I only have a Mac, so it's tough for me to offer Windows debugging advice. It sounds like @hansireit might be able to help you on Windows though

[GrizzlyEnglish]

@dylhunn Thanks! I have it all done, except one use case -> ngFor renaming elements being marked as dupes. Once I get that figured out should be good, unless @phalgunv still wants to work it; I don't mean to snatch it.

[phalgunv]

Thanks @dylhunn. I was stuck with for quite a long time due to build issues on Windows I have now switched to Ubuntu(via WSL).

@GrizzlyEnglish, I was probably only halfway through the changes and may not be able to get completed before you. So it seems fair if you'd continue with the fix.

[dylhunn]

Glad to hear you're working on this! No rush, but please send it my way and/or ping me when you want a review!

[GrizzlyEnglish]

@dylhunn Not sure if directed at me; but, I do have a PR open in draft (there was a bit of review done) and I seem to not have access to re-open the PR. Can you peek it and reopen please?

[dylhunn]

@GrizzlyEnglish I have reopened #46994. Is it ready for review? Edit: yes; convo continued on the PR

[dylhunn]

Unmarking as help wanted, since we have an almost-done PR that's likely to be finished soonish

[vp4140]

Hey @dylhunn , I'm interested in continuing working on the above mentioned PR.