FEATURE: Treat emoji or similar characters as one (#12482)

Long messages consisting only of emojis, dots or commas used to be
valid because character-wise they were over the limit.

spec/components/validators/post_validator_spec.rb

@@ -52,6 +52,33 @@ describe PostValidator do
       expect(post.errors.count).to eq(1)
     end
 
+    it "counts emoji as a single character" do
+      post.raw = ":smiling_face_with_three_hearts:" * (SiteSetting.min_post_length - 1)
+      validator.stripped_length(post)
+      expect(post.errors.count).to eq(1)
+
+      post = build(:post, topic: topic)
+      post.raw = ":smiling_face_with_three_hearts:" * SiteSetting.min_post_length
+      validator.stripped_length(post)
+      expect(post.errors.count).to eq(0)
+    end
+
+    it "counts multiple characters as a single character" do
+      post.raw = "." * SiteSetting.min_post_length
+      validator.stripped_length(post)
+      expect(post.errors.count).to eq(1)
+
+      post = build(:post, topic: topic)
+      post.raw = "," * SiteSetting.min_post_length
+      validator.stripped_length(post)
+      expect(post.errors.count).to eq(1)
+
+      post = build(:post, topic: topic)
+      post.raw = "<!-- #{'very long comment' * SiteSetting.min_post_length} -->"
+      validator.stripped_length(post)
+      expect(post.errors.count).to eq(1)
+    end
+
     it "adds no error for long raw" do
       post.raw = "this is a long topic body testing 123"
       validator.stripped_length(post)