Asynchronous resolution of validation messages

[0cv]

**I'm submitting a Feature (or Support) request ** (check one with "x")

[ ] bug report => search github for a similar issue or PR before submitting
[ x ] feature request
[ x ] support request

Current behavior
This is possible to customise validation messages in the forRoot function. However, even so it's possible to tweak the messages a bit by using a synchronous function, this does not seem possible to resolve messages asynchronously, through e.g. Observable (let me know if I missed something).

Expected behavior
Depending on the user language filling the form, it would be great to have an advanced customisation of error messages. Observable would give the possibility to fetch data possibly remotely.

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

[0cv]

Guess I found something which fulfils partially what I'm asking: https://github.com/formly-js/ng2-formly/blob/503e803e27896f73042ef3024cad8321adf4a749/demo/hello.ts#L221

         validators: {
            city: {
              expression: (control: FormControl) => control.value && control.value.length > 3,
              message: `City: Should have atleast 3 Characters`,
            },
          },

But it seems to only work when an expression is specified as well. Is there anything else?

[mohammedzamakhan]

There's #307 that's in the pipeline. We hope that someone can help us with it by making their first PR for the repo 😁

[0cv]

This sounds good, but I'm not sure that's exactly the same. Does Field.level.messages applies at Form or at Field level? In my case, I'm not looking specifically at customising the message at field level, but instead looking at customising generic error messages, at least at Form level or ideally at application level (e.g. the error message for required or minLength). A bit like this https://github.com/formly-js/ng2-formly/blob/master/demo/validation.service.ts#L6-L9

[mohammedzamakhan]

For that you always have setValidator in FormlyConfig https://github.com/formly-js/ng2-formly/blob/master/src/core/services/formly.config.ts#L138

[0cv]

We are getting closer. So much like this in forRoot, but instead directly in the component https://github.com/formly-js/ng2-formly/blob/master/demo/hello.ts#L552 ? However this does not seem to be the place where the messages can be customized, isn't it? Feels like setValidationMessages or similar is missing on FormlyConfig

[mohammedzamakhan]

Makes sense 👍 I thought there is already a way for that. Can you make a PR for that?

[0cv]

While trying to make the PR, I realized that actually it already exists... Just need to include the service private validationMessages: FormlyValidationMessages in the Component constructor and then for example in ngOnInit to configure the required message: this.validationMessages.addStringMessage('required', 'Field required!');

It works also when wrapped into a setTimeout so ultimately, that's all what's needed I guess

[rogercoder]

Using ngx-formly 4.8.0, you now include private formlyConfig: FormlyConfig in your constructor, and then, in ngOnInit():

this.formlyConfig.addValidatorMessage("required", 'This field is required');