#428

frontend/src/pages/help/HelpDiffPage.tsx

@@ -30,17 +30,19 @@ const HelpDiffPage: FC = () => {
       queryKey: helpKeys.article (identifier),
       queryFn: () => getHelpArticle (identifier),
       staleTime: Infinity })
-  const language = resolveHelpLanguage (article, localeLanguage (locale))
+  const requestedLanguage = localeLanguage (locale)
+  const language = resolveHelpLanguage (article, requestedLanguage)
   const validParams = Boolean (identifier && from && to)
       && searchParams.getAll ('from').length === 1
       && searchParams.getAll ('to').length === 1
   const { data: diff, isLoading, isError } = useQuery ({
-      enabled: validParams && article != null,
-      queryKey: helpKeys.diff (identifier, language, from, to),
-      queryFn: () => getHelpDiff (identifier, language, from, to),
+      enabled: validParams && language != null,
+      queryKey: helpKeys.diff (identifier, requestedLanguage, from, to),
+      queryFn: () => getHelpDiff (identifier, requestedLanguage, from, to),
       staleTime: Infinity })
 
-  if (!(validParams) || isError || (!(isLoading) && diff == null))
+  if (!(validParams) || (article != null && language == null)
+      || isError || (!(isLoading) && diff == null))
     return <NotFound/>
 
   const title = `${ diff?.to.title ?? identifier } (${ from } → ${ to })`
@@ -65,7 +67,7 @@ const HelpDiffPage: FC = () => {
 		  {diff.to.title} ({to})
 		</PrefetchLink>
 	      </div>
-	      <pre lang={language} className="mt-4 overflow-x-auto whitespace-pre">
+	      <pre lang={requestedLanguage} className="mt-4 overflow-x-auto whitespace-pre">
 		<code>
 		  {diff.lines.map ((line, index) => {
 		    const colour = cn (