post_status_form: inherit language from parent

If I'm replying to a post in Klingon, chances are I'm going to write in
Klingon. This reduces friction for properly marking post language in a
conversation.

src/components/post_status_form/post_status_form.js

@@ -85,6 +85,7 @@ const PostStatusForm = {
     'quoteId',
     'repliedUser',
     'attentions',
+    'copyMessageLanguage',
     'copyMessageScope',
     'subject',
     'disableSubject',
@@ -153,8 +154,7 @@ const PostStatusForm = {
       statusText = buildMentionsString({ user: this.repliedUser, attentions: this.attentions }, currentUser)
     }
 
-    const { postContentType: contentType, postLanguage: defaultPostLanguage, sensitiveByDefault, sensitiveIfSubject, interfaceLanguage, alwaysShowSubjectInput } = this.$store.getters.mergedConfig
-    const postLanguage = defaultPostLanguage || interfaceToISOLanguage(interfaceLanguage)
+    const { postContentType: contentType, sensitiveByDefault, sensitiveIfSubject, alwaysShowSubjectInput } = this.$store.getters.mergedConfig
 
     let statusParams = {
       spoilerText: this.subject || '',
@@ -165,7 +165,7 @@ const PostStatusForm = {
       poll: {},
       mediaDescriptions: {},
       visibility: this.suggestedVisibility(),
-      language: postLanguage,
+      language: this.suggestedLanguage(),
       contentType
     }
 
@@ -180,7 +180,7 @@ const PostStatusForm = {
         poll: this.statusPoll || {},
         mediaDescriptions: this.statusMediaDescriptions || {},
         visibility: this.statusScope || this.suggestedVisibility(),
-        language: this.statusLanguage || postLanguage,
+        language: this.statusLanguage || this.suggestedLanguage(),
         contentType: statusContentType
       }
     }
@@ -342,7 +342,6 @@ const PostStatusForm = {
     },
     clearStatus () {
       const config = this.$store.getters.mergedConfig
-      const postLanguage = config.postLanguage || interfaceToISOLanguage(config.interfaceLanguage)
       this.newStatus = {
         status: '',
         spoilerText: '',
@@ -350,7 +349,7 @@ const PostStatusForm = {
         nsfw: !!config.sensitiveByDefault,
         visibility: this.suggestedVisibility(),
         contentType: config.postContentType,
-        language: postLanguage,
+        language: this.suggestedLanguage(),
         poll: {},
         mediaDescriptions: {}
       }
@@ -766,6 +765,15 @@ const PostStatusForm = {
     openProfileTab () {
       this.$store.dispatch('openSettingsModalTab', 'profile')
     },
+    suggestedLanguage () {
+      // Make sure the inherited language is actually valid
+      if (this.postLanguageOptions.find(o => o.value === this.copyMessageLanguage)) {
+        return this.copyMessageLanguage
+      }
+      const { postLanguage: defaultPostLanguage, interfaceLanguage } = this.$store.getters.mergedConfig
+      const postLanguage = defaultPostLanguage || interfaceToISOLanguage(interfaceLanguage)
+      return postLanguage
+    },
     suggestedVisibility () {
       if (this.copyMessageScope) {
         if (this.copyMessageScope === 'direct') {

src/components/status/status.vue

@@ -519,6 +519,7 @@
           :reply-to="status.id"
           :attentions="status.attentions"
           :replied-user="status.user"
+          :copy-message-language="status.language"
           :copy-message-scope="status.visibility"
           :subject="replySubject"
           @posted="toggleReplying"
@@ -533,6 +534,7 @@
           :quote-id="status.id"
           :attentions="[status.user]"
           :replied-user="status.user"
+          :copy-message-language="status.language"
           :copy-message-scope="status.visibility"
           :subject="replySubject"
           @posted="toggleQuoting"

src/services/entity_normalizer/entity_normalizer.service.js

@@ -326,6 +326,7 @@ export const parseStatus = (data) => {
     }
     output.pinned = data.pinned
     output.muted = data.muted
+    output.language = data.language
   } else {
     output.favorited = data.favorited
     output.fave_num = data.fave_num