DEV: Truncate user agent string when it is too long instead of null (#27758)

This is a follow up to 005f623c42 where
we want to truncate the user agent string instead of nulling out the
column when the user agent string is too low. By truncating, we still
get to retain information that can still be useful.

app/models/search_log.rb

@@ -1,7 +1,10 @@
 # frozen_string_literal: true
 
 class SearchLog < ActiveRecord::Base
+  MAXIMUM_USER_AGENT_LENGTH = 2000
+
   validates_presence_of :term
+  validates :user_agent, length: { maximum: MAXIMUM_USER_AGENT_LENGTH }
 
   belongs_to :user
 
@@ -41,7 +44,9 @@ class SearchLog < ActiveRecord::Base
     ip_address = nil if user_id
     key = redis_key(user_id: user_id, ip_address: ip_address)
 
-    user_agent = nil if user_agent && user_agent.length > 2000
+    if user_agent && user_agent.length > MAXIMUM_USER_AGENT_LENGTH
+      user_agent = user_agent.truncate(MAXIMUM_USER_AGENT_LENGTH, omission: "")
+    end
 
     result = nil
 

spec/models/search_log_spec.rb

@@ -7,30 +7,30 @@ RSpec.describe SearchLog, type: :model do
     context "with invalid arguments" do
       it "no search type returns error" do
         status, _ =
-          SearchLog.log(
-            term: "bounty hunter",
-            search_type: :missing,
-            ip_address: "127.0.0.1",
-            user_agent: "Mozilla",
-          )
+          SearchLog.log(term: "bounty hunter", search_type: :missing, ip_address: "127.0.0.1")
+
         expect(status).to eq(:error)
       end
 
       it "no IP returns error" do
+        status, _ = SearchLog.log(term: "bounty hunter", search_type: :header, ip_address: nil)
+
+        expect(status).to eq(:error)
+      end
+
+      it "truncates the `user_agent` attribute if it exceeds #{described_class::MAXIMUM_USER_AGENT_LENGTH} characters" do
+        user_agent = "a" * (described_class::MAXIMUM_USER_AGENT_LENGTH + 1)
+
         status, _ =
           SearchLog.log(
             term: "bounty hunter",
             search_type: :header,
-            ip_address: nil,
-            user_agent: "Mozilla",
+            user_agent:,
+            ip_address: "127.0.0.1",
           )
-        expect(status).to eq(:error)
-      end
 
-      it "does not error when no user_agent" do
-        status, _ =
-          SearchLog.log(term: "bounty hunter", search_type: :header, ip_address: "127.0.0.1")
         expect(status).to eq(:created)
+        expect(SearchLog.last.user_agent).to eq("a" * described_class::MAXIMUM_USER_AGENT_LENGTH)
       end
     end