[core] Copy getClasses from the core (removed in v5)

[flaviendelangle]

#1994 starts using getClasses that was recently removed from the core (due to the migration away from enzyme)
See mui/material-ui@2569eb9#diff-f075d81b14df1f31fb0699c4516fe3d78490351867feeb4fb869d5dbe8c6128e

@oliviertassinari

[flaviendelangle]

https://app.circleci.com/pipelines/github/mui-org/material-ui-x/6063/workflows/274e60b1-d36b-4d0d-a6be-dbb0b3222d88/jobs/31907

Copy paste doen't work, I'll try to fix

[oliviertassinari]

Ok, so if this quick-win doesn't work. I would propose even simpler. We introduce the xxxClasses pattern for this component, it will help us migrate to v5, and avoid investing in legacy test utils.

[oliviertassinari]

Here is what we do in v5 (in the idea):

diff --git a/packages/grid/_modules_/grid/components/panel/GridPanel.test.tsx b/packages/grid/_modules_/grid/components/panel/GridPanel.test.tsx
index bf5027df..b8d6e468 100644
--- a/packages/grid/_modules_/grid/components/panel/GridPanel.test.tsx
+++ b/packages/grid/_modules_/grid/components/panel/GridPanel.test.tsx
@@ -4,11 +4,9 @@ import {
   // @ts-expect-error JS
   createMount,
   // @ts-expect-error JS
-  getClasses,
-  // @ts-expect-error JS
   describeConformance,
 } from 'test/utils';
-import { GridPanel, useGridApiRef, GridApiContext } from '@material-ui/data-grid';
+import { GridPanel, gridPanelClasses as classes, useGridApiRef, GridApiContext } from '@material-ui/data-grid';
 import { Popper } from '@material-ui/core';

 describe('<GridPanel />', () => {
@@ -16,8 +14,6 @@ describe('<GridPanel />', () => {
   // TODO v5: replace with createClientRender
   const render = createClientRenderStrictMode();

-  let classes;
-
   function Wrapper(props) {
     const apiRef = useGridApiRef();
     apiRef.current.columnHeadersContainerElementRef = {
@@ -28,10 +24,6 @@ describe('<GridPanel />', () => {
     return <GridApiContext.Provider value={apiRef} {...props} />;
   }

-  before(() => {
-    classes = getClasses(<GridPanel open={false} />);
-  });
-
   describeConformance(<GridPanel disablePortal open />, () => ({
     classes,
     inheritComponent: Popper,
diff --git a/packages/grid/_modules_/grid/components/panel/GridPanel.tsx b/packages/grid/_modules_/grid/components/panel/GridPanel.tsx
index 7f5416ed..ac458b4a 100644
--- a/packages/grid/_modules_/grid/components/panel/GridPanel.tsx
+++ b/packages/grid/_modules_/grid/components/panel/GridPanel.tsx
@@ -41,6 +41,11 @@ const useStyles = makeStyles(
   { name: 'MuiGridPanel', defaultTheme },
 );

+export const gridPanelClasses = {
+  root: 'MuiGridPanel-root',
+  paper: 'MuiGridPanel-paper',
+};
+
 export const GridPanel = React.forwardRef<HTMLDivElement, GridPanelProps>(function GridPanel(
   props,
   ref,
@@ -103,6 +108,3 @@ export const GridPanel = React.forwardRef<HTMLDivElement, GridPanelProps>(functi
     </Popper>
   );
 }) as (props: GridPanelProps) => JSX.Element;
-
-// @ts-ignore TODO migrate to v5 gridPanelClasses pattern, this is only for tests
-GridPanel.useStyles = useStyles;

If you want to push it further, to match v5 exactly, feel free to.

[oliviertassinari]

@mui-org/x think that we need to take over this effort as Flavien is off until next Monday.

[m4theushw]

@oliviertassinari I can take it as it's breaking master and blocking all new PRs.

[m4theushw]

@oliviertassinari Do you have any suggestion to fix the Netlify deploy? I think it fails because it's using a node_modules cache.

[oliviertassinari]

@m4theushw It's flaky, I don't know why. I have rerun it.

[oliviertassinari]

It's green 🎉

[oliviertassinari]

@m4theushw Thanks. I'm rebasing my other PR now :)