Merge pull request rails#50104 from joshuay03/improve-adapter-not-found-error-message

Improve `AdapterNotFound` error message

Author: byroot

activerecord/lib/active_record/connection_adapters.rb

@@ -23,28 +23,32 @@ def register(name, class_name, path = class_name.underscore)
 
       def resolve(adapter_name) # :nodoc:
         # Require the adapter itself and give useful feedback about
-        #   1. Missing adapter gems and
-        #   2. Adapter gems' missing dependencies.
+        #   1. Missing adapter gems.
+        #   2. Incorrectly registered adapters.
+        #   3. Adapter gems' missing dependencies.
         class_name, path_to_adapter = @adapters[adapter_name]
 
         unless class_name
-          raise AdapterNotFound, "database configuration specifies nonexistent '#{adapter_name}' adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile."
+          raise AdapterNotFound, <<~MSG.squish
+            Database configuration specifies nonexistent '#{adapter_name}' adapter.
+            Available adapters are: #{@adapters.keys.sort.join(", ")}.
+            Ensure that the adapter is spelled correctly in config/database.yml or that you've added the necessary
+            adapter gem to your Gemfile if it's not in the list of available adapters.
+          MSG
         end
 
         unless Object.const_defined?(class_name)
           begin
             require path_to_adapter
           rescue LoadError => error
-            # We couldn't require the adapter itself. Raise an exception that
-            # points out config typos and missing gems.
+            # We couldn't require the adapter itself.
             if error.path == path_to_adapter
-              # We can assume that a non-builtin adapter was specified, so it's
-              # either misspelled or missing from Gemfile.
-              raise LoadError, "Error loading the '#{adapter_name}' Active Record adapter. Ensure that the necessary adapter gem is in the Gemfile. #{error.message}", error.backtrace
-
+              # We can assume here that a non-builtin adapter was specified and the path
+              # registered by the adapter gem is incorrect.
+              raise LoadError, "Error loading the '#{adapter_name}' Active Record adapter. Ensure that the path registered by the adapter gem is correct. #{error.message}", error.backtrace
+            else
               # Bubbled up from the adapter require. Prefix the exception message
               # with some guidance about how to address it and reraise.
-            else
               raise LoadError, "Error loading the '#{adapter_name}' Active Record adapter. Missing a gem it depends on? #{error.message}", error.backtrace
             end
           end

activerecord/test/cases/database_configurations/resolver_test.rb

@@ -16,7 +16,7 @@ def test_url_invalid_adapter
             Base.connection_handler.establish_connection "ridiculous://foo?encoding=utf8"
           end
 
-          assert_match "database configuration specifies nonexistent 'ridiculous' adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", error.message
+          assert_match "Database configuration specifies nonexistent 'ridiculous' adapter. Available adapters are: abstract, fake, mysql2, postgresql, sqlite3, trilogy. Ensure that the adapter is spelled correctly in config/database.yml or that you've added the necessary adapter gem to your Gemfile if it's not in the list of available adapters.", error.message
         end
 
         # The abstract adapter is used simply to bypass the bit of code that

railties/test/commands/dbconsole_test.rb

@@ -120,7 +120,7 @@ def test_start
   def test_unknown_command_line_client
     start(adapter: "unknown", database: "db")
     assert aborted
-    assert_match(/database configuration specifies nonexistent 'unknown' adapter/, output)
+    assert_match(/Database configuration specifies nonexistent 'unknown' adapter/, output)
   end
 
   def test_primary_is_automatically_picked_with_3_level_configuration