Typography variantMapping should merge with the default value

Duplicates

• I have searched the existing issues

Latest version

• I have tested the latest version

Current behavior 😯

variantMapping es sobreescrito por defaultVariantMapping estropeando la variantMapping propiedad.

https://github.com/mui/material-ui/blob/92a4866ce9a06769592cddc06cfa7455b4644544/packages/mui-material/src/Typography/Typography.js#L102

Se podría cambiar esta linea por
variantMapping["defaultVariantMapping"] = defaultVariantMapping,

En esta linea variantMapping[variant] no se lee nunca porque las propiedades quedan sobre escritas.
https://github.com/mui/material-ui/blob/92a4866ce9a06769592cddc06cfa7455b4644544/packages/mui-material/src/Typography/Typography.js#L121

Expected behavior 🤔

Que variantMapping funcione de manera correcta, sin tener que usar la api de componentes.

Steps to reproduce 🕹

Crear un tema y probar las opciones de typography con diferentes api
typography: {

fontFamily: "libre franklin",
"em":styleText(400 ,{name: "backgroundColor", value:"lawngreen"}),
/*
variantMapping: {
  "em": 'em',
},*/
defaultProps: {
  variantMapping: {
    "em": 'em',
  },
},

},

components: {
MuiTypography: {

  variants: [
    {
        props: { variant: 'mark' },
        style: {
          backgroundColor:"lightskyblue",
        },
    },
  ],

/* Nofunciona
variantMapping: {
"mark": 'mark',
},
*/
defaultProps: {
variantMapping: {
subtitle1: 'header',
subtitle2: 'header',
"mark": 'mark',
"em": 'em',
},
},
},
},

Context 🔦

Al ver porque usabais defaultProps me di cuenta de este error.

Your environment 🌎

No response

Start in packages/mui-material/src/Typography/Typography.js at the referenced lines and reproduce the issue with a theme's Typography defaultProps and variantMapping. Verify how the default mapping is applied and confirm that custom variant entries remain available alongside defaults when the fix is complete.