vuetifyjs · DerYeger · Dec 19, 2024
diff --git a/packages/docs/src/pages/en/features/theme.md b/packages/docs/src/pages/en/features/theme.md
@@ -350,4 +350,10 @@ export const vuetify = createVuetify({
 
 ## Implementation
 
-Vuetify generates theme styles at runtime according to the given configuration. The generated styles are injected into the `<head>` section of the DOM in a `<style>` tag with an **id** of `vuetify-theme-stylesheet`.
+Vuetify generates theme styles at runtime according to the given configuration. The generated styles are injected into the `<head>` section of the DOM in a `<style>` tag with a default **id** of `vuetify-theme-stylesheet`.
+
+### Microfrontends
+
+An application using microfrontends with multiple instances of Vuetify may need to define unique **theme.stylesheetId** values for each microfrontend in order to prevent conflicts between their generated stylesheets.
+Further, such a scenario might require styles to be scoped to a specific microfrontend, which can be achieved by setting the **theme.scope** property.
+For example, a microfrontend mounted in an element `#my-app` can define a **theme.scope** of `#my-app` to scope its styles to that element and its children instead of `:root` and global classes.
diff --git a/packages/vuetify/src/composables/__tests__/theme.spec.ts b/packages/vuetify/src/composables/__tests__/theme.spec.ts
@@ -148,6 +148,33 @@ describe('createTheme', () => {
     expect(theme.computedThemes.value.light.colors).toHaveProperty('color2-lighten-1')
   })
 
+  it('should allow for customization of the stylesheet id', () => {
+    const customStylesheetId = 'custom-vuetify-stylesheet-id'
+    const theme = createTheme({
+      stylesheetId: customStylesheetId,
+    })
+
+    theme.install(app)
+
+    expect(document.getElementById(customStylesheetId)).toBeDefined()
+  })
+
+  it('should allow for themes to be scoped', () => {
+    const scope = '#my-app'
+    const theme = createTheme({
+      scope,
+    })
+
+    theme.install(app)
+
+    const scopedStyles = document.getElementById('vuetify-theme-stylesheet')!.innerHTML
+    const selectors = scopedStyles.split('\n').filter(line => line.includes('{')).map(line => line.trim())
+    selectors.forEach(selector => {
+      expect(selector.startsWith(`:where(${scope})`)).toBe(true)
+      expect(selector).not.toContain(':root')
+    })
+  })
+
   // it('should use [email protected] functionality', () => {
   //   const theme = createTheme()
   //   const set = jest.fn()

diff --git a/packages/vuetify/src/composables/theme.ts b/packages/vuetify/src/composables/theme.ts
@@ -33,6 +33,8 @@ export type ThemeOptions = false | {
   defaultTheme?: string
   variations?: false | VariationsOptions
   themes?: Record<string, ThemeDefinition>
+  stylesheetId?: string
+  scope?: string
 }
 export type ThemeDefinition = DeepPartial<InternalThemeDefinition>
 
@@ -42,6 +44,8 @@ interface InternalThemeOptions {
   defaultTheme: string
   variations: false | VariationsOptions
   themes: Record<string, InternalThemeDefinition>
+  stylesheetId: string
+  scope?: string
 }
 
 interface VariationsOptions {
@@ -185,6 +189,7 @@ function genDefaults () {
         },
       },
     },
+    stylesheetId: 'vuetify-theme-stylesheet',
   }
 }
 
@@ -252,6 +257,25 @@ export function createTheme (options?: ThemeOptions): ThemeInstance & { install:
   })
   const current = computed(() => computedThemes.value[name.value])
 
+  function createCssClass (lines: string[], selector: string, content: string[]) {
+    lines.push(
+      `${getScopedSelector(selector)} {\n`,
+      ...content.map(line => `  ${line};\n`),
+      '}\n',
+    )
+  }
+
+  function getScopedSelector (selector: string) {
+    if (!parsedOptions.scope) {
+      return selector
+    }
+    const scopeSelector = `:where(${parsedOptions.scope})`
+    if (selector === ':root') {
+      return scopeSelector
+    }
+    return `${scopeSelector} ${selector}`
+  }
+
   const styles = computed(() => {
     const lines: string[] = []
 
@@ -295,7 +319,7 @@ export function createTheme (options?: ThemeOptions): ThemeInstance & { install:
     return {
       style: [{
         children: styles.value,
-        id: 'vuetify-theme-stylesheet',
+        id: parsedOptions.stylesheetId,
         nonce: parsedOptions.cspNonce || false as never,
       }],
     }
@@ -321,7 +345,7 @@ export function createTheme (options?: ThemeOptions): ThemeInstance & { install:
       }
     } else {
       let styleEl = IN_BROWSER
-        ? document.getElementById('vuetify-theme-stylesheet')
+        ? document.getElementById(parsedOptions.stylesheetId)
         : null
 
       if (IN_BROWSER) {
@@ -334,7 +358,7 @@ export function createTheme (options?: ThemeOptions): ThemeInstance & { install:
         if (typeof document !== 'undefined' && !styleEl) {
           const el = document.createElement('style')
           el.type = 'text/css'
-          el.id = 'vuetify-theme-stylesheet'
+          el.id = parsedOptions.stylesheetId
           if (parsedOptions.cspNonce) el.setAttribute('nonce', parsedOptions.cspNonce)
 
           styleEl = el
@@ -400,14 +424,6 @@ export function useTheme () {
   return theme
 }
 
-function createCssClass (lines: string[], selector: string, content: string[]) {
-  lines.push(
-    `${selector} {\n`,
-    ...content.map(line => `  ${line};\n`),
-    '}\n',
-  )
-}
-
 function genCssVariables (theme: InternalThemeDefinition) {
   const lightOverlay = theme.dark ? 2 : 1
   const darkOverlay = theme.dark ? 1 : 2