[FormHelperText] Error styles should override disabled styles

[matthewdordal]

Material UI is a great project so just looking to help out.

According to the issue the error styles in the FormHelperText take precedence over the disabled styles. Please let me know if there is further changes that are required. If this is not an actual issue also feel free to close the PR.

Before this PR here was the behavior:

Example Code:

<TextField
          error
          disabled
          id="standard-disabled"
          label="Disabled"
          defaultValue="Hello World"
          className={classes.textField}
          margin="normal"
          helperText="Some helper text"
 />

Before this PR:

After this PR:

Closes #13210

[mbrookes]

@matthewdordal Please could you follow the issue title / commit message format we use elsewhere?

"[ComponentName] Imperative commit message"

[matthewdordal]

@mbrookes sorry that I missed the commit message format. I updated the commit message. Please let me know if there's any other things I should update. 😸

[oliviertassinari]

I can confirm the same behavior with Bootstrap. It makes sense. In some way, this change can be seen as breaking, but I like to think it's a bug fix, solving a usability problem.

[oliviertassinari]

Let's wait for the next minor v3.3.0.

[mbrookes]

@oliviertassinari I agree with you that this is more of a bugfix, however I'm not sure how much sense it makes (the behavior, rather than the fix per se). How can you fix an error on a disabled input?!

[jiayuandeng]

@mbrookes The error could be fixed by another component. Here is a case:

Assume a user can use the Select (<TextField select />) to select from some uploaded files (like using file IDs). If there is no file to select, the Select is disabled, and an error message shows when the user tries to submit the form. To fix the error, the user can click a button next to it to upload a file. Once a file is uploaded, the select is not disabled anymore.

[oliviertassinari]

@matthewdordal It's a great first pull request on Material-UI 👌🏻. Thank you for working on it!