feat(language-filter): implement fallback component for language-filt…

…er (#3204)

(identical implementation to the i18n plugin)

packages/@sanity/language-filter/src/SelectLanguageProvider.tsx

@@ -1,10 +1,11 @@
 // @todo: remove the following line when part imports has been removed from this file
 ///<reference types="@sanity/types/parts" />
 
-import React, {useRef, useEffect, useState} from 'react'
+import React, {useRef, useEffect, useState, useMemo} from 'react'
 import config from 'part:@sanity/language-filter/config'
 import {SchemaType} from '@sanity/types'
 import {Subscription} from 'rxjs'
+import languageFilterImplementations from 'all:part:@sanity/desk-tool/language-select-component'
 import {selectedLanguages$, setLangs} from './datastore'
 import SelectLanguage from './SelectLanguage'
 
@@ -16,6 +17,20 @@ const SelectLanguageProvider = ({schemaType}: Props) => {
   const subscriptionRef$ = useRef<Subscription | null>(null)
   const [selected, setSelected] = useState<string[]>([])
   const [currentDocumentType, setCurrentDocumentType] = useState<string | undefined>()
+  const shouldShow = useMemo(() => {
+    const {documentTypes} = config
+    return !!(documentTypes && schemaType?.name && documentTypes.includes(schemaType.name))
+  }, [schemaType])
+  const FallbackImplementation = useMemo(() => {
+    if (languageFilterImplementations && Array.isArray(languageFilterImplementations)) {
+      return (
+        languageFilterImplementations?.filter(
+          (component) => SelectLanguageProvider !== component
+        )?.[0] ?? null
+      )
+    }
+    return null
+  }, [])
 
   useEffect(() => {
     setCurrentDocumentType(schemaType?.name)
@@ -32,16 +47,24 @@ const SelectLanguageProvider = ({schemaType}: Props) => {
     }
   }, [])
 
-  return (
-    <SelectLanguage
-      languages={config.supportedLanguages}
-      defaultLanguages={config.defaultLanguages}
-      documentTypes={config.documentTypes}
-      currentDocumentType={currentDocumentType}
-      selected={selected}
-      onChange={setLangs}
-    />
-  )
+  if (shouldShow) {
+    return (
+      <SelectLanguage
+        languages={config.supportedLanguages}
+        defaultLanguages={config.defaultLanguages}
+        documentTypes={config.documentTypes}
+        currentDocumentType={currentDocumentType}
+        selected={selected}
+        onChange={setLangs}
+      />
+    )
+  }
+
+  if (FallbackImplementation) {
+    return <FallbackImplementation schemaType={schemaType} />
+  }
+
+  return null
 }
 
 export default SelectLanguageProvider

packages/@sanity/types/parts/part.@sanity/language-filter/language-filter.d.ts

@@ -1,3 +1,12 @@
+declare module 'all:part:@sanity/desk-tool/language-select-component' {
+  const implementations:
+    | React.FC<{
+        schemaType?: import('@sanity/types').SchemaType
+      }>[]
+    | undefined
+  export default implementations
+}
+
 declare module 'part:@sanity/language-filter/config' {
   interface Config {
     supportedLanguages: {