Make inapplicable_reason text to be reusable

We also need to display the inapplicable_reason text in another
place (`Gitlab::Suggestions::SuggestionSet`).

There's no need to return `inapplicable_reason` as symbol for now
so it was converted to return text instead.

app/models/suggestion.rb

@@ -43,12 +43,12 @@ class Suggestion < ApplicationRecord
 
   def inapplicable_reason(cached: true)
     strong_memoize("inapplicable_reason_#{cached}") do
-      next :applied if applied?
-      next :merge_request_merged if noteable.merged?
-      next :merge_request_closed if noteable.closed?
-      next :source_branch_deleted unless noteable.source_branch_exists?
-      next :outdated if outdated?(cached: cached) || !note.active?
-      next :same_content unless different_content?
+      next _("Can't apply this suggestion.") if applied?
+      next _("This merge request was merged. To apply this suggestion, edit this file directly.") if noteable.merged?
+      next _("This merge request is closed. To apply this suggestion, edit this file directly.") if noteable.closed?
+      next _("Can't apply as the source branch was deleted.") unless noteable.source_branch_exists?
+      next outdated_reason if outdated?(cached: cached) || !note.active?
+      next _("This suggestion already matches its content.") unless different_content?
     end
   end
 
@@ -73,4 +73,12 @@ class Suggestion < ApplicationRecord
   def different_content?
     from_content != to_content
   end
+
+  def outdated_reason
+    if single_line?
+      _("Can't apply as this line was changed in a more recent version.")
+    else
+      _("Can't apply as these lines were changed in a more recent version.")
+    end
+  end
 end

app/serializers/suggestion_entity.rb

@@ -16,24 +16,8 @@ class SuggestionEntity < API::Entities::Suggestion
 
   expose :inapplicable_reason do |suggestion|
     next _("You don't have write access to the source branch.") unless can_apply?(suggestion)
-    next if suggestion.appliable?
 
-    case suggestion.inapplicable_reason
-    when :merge_request_merged
-      _("This merge request was merged. To apply this suggestion, edit this file directly.")
-    when :merge_request_closed
-      _("This merge request is closed. To apply this suggestion, edit this file directly.")
-    when :source_branch_deleted
-      _("Can't apply as the source branch was deleted.")
-    when :outdated
-      phrase = suggestion.single_line? ? 'this line was' : 'these lines were'
-
-      _("Can't apply as %{phrase} changed in a more recent version.") % { phrase: phrase }
-    when :same_content
-      _("This suggestion already matches its content.")
-    else
-      _("Can't apply this suggestion.")
-    end
+    suggestion.inapplicable_reason
   end
 
   private

locale/gitlab.pot

@@ -4134,10 +4134,13 @@ msgstr ""
 msgid "Can override approvers and approvals required per merge request"
 msgstr ""
 
-msgid "Can't apply as %{phrase} changed in a more recent version."
+msgid "Can't apply as the source branch was deleted."
 msgstr ""
 
-msgid "Can't apply as the source branch was deleted."
+msgid "Can't apply as these lines were changed in a more recent version."
+msgstr ""
+
+msgid "Can't apply as this line was changed in a more recent version."
 msgstr ""
 
 msgid "Can't apply this suggestion."

spec/models/suggestion_spec.rb

@@ -53,7 +53,7 @@ RSpec.describe Suggestion do
     end
 
     context 'when inapplicable_reason is not nil' do
-      let(:inapplicable_reason) { :applied }
+      let(:inapplicable_reason) { "Can't apply this suggestion." }
 
       it { is_expected.to be_falsey }
     end
@@ -77,7 +77,7 @@ RSpec.describe Suggestion do
     context 'when suggestion is already applied' do
       let(:suggestion) { build(:suggestion, :applied, note: note) }
 
-      it { is_expected.to eq(:applied) }
+      it { is_expected.to eq("Can't apply this suggestion.") }
     end
 
     context 'when merge request was merged' do
@@ -85,7 +85,7 @@ RSpec.describe Suggestion do
         merge_request.mark_as_merged!
       end
 
-      it { is_expected.to eq(:merge_request_merged) }
+      it { is_expected.to eq("This merge request was merged. To apply this suggestion, edit this file directly.") }
     end
 
     context 'when merge request is closed' do
@@ -93,7 +93,7 @@ RSpec.describe Suggestion do
         merge_request.close!
       end
 
-      it { is_expected.to eq(:merge_request_closed) }
+      it { is_expected.to eq("This merge request is closed. To apply this suggestion, edit this file directly.") }
     end
 
     context 'when source branch is deleted' do
@@ -101,23 +101,51 @@ RSpec.describe Suggestion do
         merge_request.project.repository.rm_branch(merge_request.author, merge_request.source_branch)
       end
 
-      it { is_expected.to eq(:source_branch_deleted) }
+      it { is_expected.to eq("Can't apply as the source branch was deleted.") }
     end
 
-    context 'when content is outdated' do
-      before do
-        allow(suggestion).to receive(:outdated?).and_return(true)
+    context 'when outdated' do
+      shared_examples_for 'outdated suggestion' do
+        before do
+          allow(suggestion).to receive(:single_line?).and_return(single_line)
+        end
+
+        context 'and suggestion is for a single line' do
+          let(:single_line) { true }
+
+          it { is_expected.to eq("Can't apply as this line was changed in a more recent version.") }
+        end
+
+        context 'and suggestion is for multiple lines' do
+          let(:single_line) { false }
+
+          it { is_expected.to eq("Can't apply as these lines were changed in a more recent version.") }
+        end
       end
 
-      it { is_expected.to eq(:outdated) }
+      context 'and content is outdated' do
+        before do
+          allow(suggestion).to receive(:outdated?).and_return(true)
+        end
+
+        it_behaves_like 'outdated suggestion'
+      end
+
+      context 'and note is outdated' do
+        before do
+          allow(note).to receive(:active?).and_return(false)
+        end
+
+        it_behaves_like 'outdated suggestion'
+      end
     end
 
-    context 'when note is outdated' do
+    context 'when suggestion has the same content' do
       before do
-        allow(note).to receive(:active?).and_return(false)
+        allow(suggestion).to receive(:different_content?).and_return(false)
       end
 
-      it { is_expected.to eq(:outdated) }
+      it { is_expected.to eq("This suggestion already matches its content.") }
     end
 
     context 'when applicable' do

spec/serializers/suggestion_entity_spec.rb

@@ -36,87 +36,11 @@ RSpec.describe SuggestionEntity do
       let(:can_apply_suggestion) { true }
 
       before do
-        allow(suggestion).to receive(:appliable?).and_return(appliable)
+        allow(suggestion).to receive(:inapplicable_reason).and_return("Can't apply this suggestion.")
       end
 
-      context 'and suggestion is appliable' do
-        let(:appliable) { true }
-
-        it 'returns nil' do
-          expect(inapplicable_reason).to be_nil
-        end
-      end
-
-      context 'but suggestion is not applicable' do
-        let(:appliable) { false }
-
-        before do
-          allow(suggestion).to receive(:inapplicable_reason).and_return(reason)
-        end
-
-        context 'and merge request was merged' do
-          let(:reason) { :merge_request_merged }
-
-          it 'returns appropriate message' do
-            expect(inapplicable_reason).to eq("This merge request was merged. To apply this suggestion, edit this file directly.")
-          end
-        end
-
-        context 'and source branch was deleted' do
-          let(:reason) { :source_branch_deleted }
-
-          it 'returns appropriate message' do
-            expect(inapplicable_reason).to eq("Can't apply as the source branch was deleted.")
-          end
-        end
-
-        context 'and merge request is closed' do
-          let(:reason) { :merge_request_closed }
-
-          it 'returns appropriate message' do
-            expect(inapplicable_reason).to eq("This merge request is closed. To apply this suggestion, edit this file directly.")
-          end
-        end
-
-        context 'and suggestion is outdated' do
-          let(:reason) { :outdated }
-
-          before do
-            allow(suggestion).to receive(:single_line?).and_return(single_line)
-          end
-
-          context 'and suggestion is for a single line' do
-            let(:single_line) { true }
-
-            it 'returns appropriate message' do
-              expect(inapplicable_reason).to eq("Can't apply as this line was changed in a more recent version.")
-            end
-          end
-
-          context 'and suggestion is for multiple lines' do
-            let(:single_line) { false }
-
-            it 'returns appropriate message' do
-              expect(inapplicable_reason).to eq("Can't apply as these lines were changed in a more recent version.")
-            end
-          end
-        end
-
-        context 'and suggestion has the same content' do
-          let(:reason) { :same_content }
-
-          it 'returns appropriate message' do
-            expect(inapplicable_reason).to eq("This suggestion already matches its content.")
-          end
-        end
-
-        context 'and suggestion is inapplicable for other reasons' do
-          let(:reason) { :some_other_reason }
-
-          it 'returns default message' do
-            expect(inapplicable_reason).to eq("Can't apply this suggestion.")
-          end
-        end
+      it 'returns the inapplicable reason' do
+        expect(inapplicable_reason).to eq(suggestion.inapplicable_reason)
       end
     end