[Container] classes generated wrongly after migration to emotion

[povilass]

1. Something interesting happening to clsx if classes.disableGutters is undefined or classes.fixed is undefined

But both combination produces just first undefined?

2. While using maxWitdh=false generates unnecessary class MuiContainer-maxWidthFalse
   

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

1. generates class MuiContainer-maxWidthFalse
2. Generates undefined classes on fixed, disableGutters properties while using clsx.

Expected Behavior 🤔

1. Using maxWitdh=false should not generate class maxWidthFalse
2. No undefined classes should be applied.

Steps to Reproduce 🕹

Updated version from "@material-ui/core": "5.0.0-alpha.21" to "@material-ui/core": "5.0.0-alpha.22"
Reference playground

Overall this probably should be changed to this.

const useUtilityClasses = (styleProps) => {
  const { classes = {}, fixed, disableGutters, maxWidth } = styleProps;

  const maxWidthClassName = `maxWidth${capitalize(String(maxWidth))}`;

  return {
    root: clsx(
      containerClasses.root,
      classes.root,
      typeof maxWidth === "string" && getContainerUtilityClass(maxWidthClassName),
      typeof maxWidth === "string" && classes[maxWidthClassName],
      fixed && containerClasses.fixed,
      fixed && classes.fixed,
      disableGutters && containerClasses.disableGutters,
      disableGutters && classes.disableGutters,
    )
  };
};

Context 🔦

Updating version.

[povilass]

@oliviertassinari has a proposal solution in #24250 (comment)

[mnajdova]

@povilass can you please share a repro where you see the undefined classes? I debugged locally the examples for the container and there aren't any undefined classes, although I don't have any overrides on the classes.

Regarding the maxWidthFalse I don't have a strong reference, but I agree, I think it makes sense not to add it when the value of the prop is false, as it would be more consistent with the other components 👍

[mnajdova]

Anyway, I agree that we should soon rather then later update the classes generation to something like it is proposed in #24250 (comment) for making sure we keep this behavior consistent across different components.

[povilass]

@mnajdova the same code just needed to uncomment old useUtilityClasses code

[mnajdova]

Should have been fixed by #24371 I believe.

[povilass]

OK let's wait for the new version for now I think we can close it.

[oliviertassinari]

@povilass developers can already test it: https://github.com/mui-org/material-ui/blob/next/CONTRIBUTING.md#how-can-i-use-a-change-that-wasnt-released-yet

[povilass]

@oliviertassinari Yes it works updated and I used https://ci.codesandbox.io/status/mui-org/material-ui/pr/24371 to find the correct pull request and how to install it to my repository.