Refactor and split ApplicationHelper#avatar_icon.

When we don't use the original `ApplicationHelper#avatar_icon` anymore, we
can just remove it (and its specs).

Closes #42800.

app/helpers/application_helper.rb

@@ -69,17 +69,27 @@ module ApplicationHelper
   end
   def avatar_icon(user_or_email = nil, size = nil, scale = 2, only_path: true)
-    user =
-      if user_or_email.is_a?(User)
-        user_or_email
-      else
-        User.find_by_any_email(user_or_email.try(:downcase))
-      end
+    if user_or_email.is_a?(User)
+      avatar_icon_for_user(user_or_email, size, scale, only_path: only_path)
+    else
+      avatar_icon_for_email(user_or_email, size, scale, only_path: only_path)
+    end
+  end
+
+  def avatar_icon_for_email(email = nil, size = nil, scale = 2, only_path: true)
+    user = User.find_by_any_email(email.try(:downcase))
+    if user
+      avatar_icon_for_user(user, size, scale, only_path: only_path)
+    else
+      gravatar_icon(email, size, scale)
+    end
+  end
+  def avatar_icon_for_user(user = nil, size = nil, scale = 2, only_path: true)
     if user
       user.avatar_url(size: size, only_path: only_path) || default_avatar
     else
-      gravatar_icon(user_or_email, size, scale)
+      gravatar_icon(nil, size, scale)
     end
   end

spec/helpers/application_helper_spec.rb

@@ -91,6 +91,54 @@ describe ApplicationHelper do
     end
   end
+  describe 'avatar_icon_for_email' do
+    let(:user) { create(:user, avatar: File.open(uploaded_image_temp_path)) }
+
+    context 'using an email' do
+      context 'when there is a matching user' do
+        it 'returns a relative URL for the avatar' do
+          expect(helper.avatar_icon_for_email(user.email).to_s)
+            .to eq(user.avatar.url)
+        end
+      end
+
+      context 'when no user exists for the email' do
+        it 'calls gravatar_icon' do
+          expect(helper).to receive(:gravatar_icon).with('foo@example.com', 20, 2)
+
+          helper.avatar_icon_for_email('foo@example.com', 20, 2)
+        end
+      end
+
+      context 'without an email passed' do
+        it 'calls gravatar_icon' do
+          expect(helper).to receive(:gravatar_icon).with(nil, 20, 2)
+
+          helper.avatar_icon_for_email(nil, 20, 2)
+        end
+      end
+    end
+  end
+
+  describe 'avatar_icon_for_user' do
+    let(:user) { create(:user, avatar: File.open(uploaded_image_temp_path)) }
+
+    context 'with a user object passed' do
+      it 'returns a relative URL for the avatar' do
+        expect(helper.avatar_icon_for_user(user).to_s)
+          .to eq(user.avatar.url)
+      end
+    end
+
+    context 'without a user object passed' do
+      it 'calls gravatar_icon' do
+        expect(helper).to receive(:gravatar_icon).with(nil, 20, 2)
+
+        helper.avatar_icon_for_user(nil, 20, 2)
+      end
+    end
+  end
+
   describe 'gravatar_icon' do
     let(:user_email) { 'user@email.com' }