AO3-6910 Report Elasticsearch syntax errors to Sentry

app/controllers/autocomplete_controller.rb

@@ -110,7 +110,8 @@ def noncanonical_tag
         body: { size: "100", query: { bool: { filter: [{ match: { tag_type: params[:type].capitalize } }, { match: { canonical: false } }], must: search_list } } }
       )
       render_output((match + search_results["hits"]["hits"].first(10).map { |t| t["_source"]["name"] }).uniq)
-    rescue Elastic::Transport::Transport::Errors::BadRequest
+    rescue Elastic::Transport::Transport::Errors::BadRequest => e
+      Sentry.capture_exception(e) if defined?(Sentry)
       render_output(match)
     end
   end

app/models/search/query.rb

@@ -14,7 +14,8 @@ def search
         body: generated_query,
         track_total_hits: true
       )
-    rescue Elastic::Transport::Transport::Errors::BadRequest
+    rescue Elastic::Transport::Transport::Errors::BadRequest => e
+      Sentry.capture_exception(e) if defined?(Sentry)
       { error: "Your search failed because of a syntax error. Please try again." }
     end
   end

spec/controllers/autocomplete_controller_spec.rb

@@ -3,6 +3,33 @@
 describe AutocompleteController do
   include LoginMacros
 
+  describe "GET #noncanonical_tag" do
+    context "when Elasticsearch raises a BadRequest error" do
+      before do
+        allow($elasticsearch).to receive(:search)
+          .and_raise(Elastic::Transport::Transport::Errors::BadRequest)
+      end
+
+      it "returns an empty result when there is no exact match" do
+        get :noncanonical_tag, params: { term: "test", type: "freeform", format: :json }
+        expect(JSON.parse(response.body)).to eq([])
+      end
+
+      it "falls back to the exact database match" do
+        create(:freeform, name: "test", canonical: false)
+        get :noncanonical_tag, params: { term: "test", type: "freeform", format: :json }
+        expect(JSON.parse(response.body)).to eq([{ "id" => "test", "name" => "test" }])
+      end
+
+      it "reports the exception to Sentry" do
+        sentry = class_double("Sentry", capture_exception: nil).as_stubbed_const
+        get :noncanonical_tag, params: { term: "test", type: "freeform", format: :json }
+        expect(sentry).to have_received(:capture_exception)
+          .with(instance_of(Elastic::Transport::Transport::Errors::BadRequest))
+      end
+    end
+  end
+
   describe "tag" do
     let!(:tag1) { create(:canonical_fandom, name: "Match") }
     let!(:tag2) { create(:canonical_fandom, name: "Blargh") }

spec/models/search/query_spec.rb

@@ -1,6 +1,27 @@
 require 'spec_helper'
 
 describe Query do
+  describe "#search" do
+    context "when Elasticsearch raises a BadRequest error" do
+      before do
+        allow($elasticsearch).to receive(:search)
+          .and_raise(Elastic::Transport::Transport::Errors::BadRequest)
+      end
+
+      it "returns an error hash" do
+        result = Query.new.search
+        expect(result).to eq(error: "Your search failed because of a syntax error. Please try again.")
+      end
+
+      it "reports the exception to Sentry" do
+        sentry = class_double("Sentry", capture_exception: nil).as_stubbed_const
+        Query.new.search
+        expect(sentry).to have_received(:capture_exception)
+          .with(instance_of(Elastic::Transport::Transport::Errors::BadRequest))
+      end
+    end
+  end
+
   describe '#split_query_text_phrases' do
     it "should add quoted phrases to a query string" do
       q = Query.new