Raise a descriptive error if the MySQL adapter fails to parse the version string.

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Raise an `ActiveRecord::ActiveRecordError` error when the MySQL database returns an invalid version string.
+
+    *Kevin McPhillips*
+
 *   `ActiveRecord::Base.transaction` now yields an `ActiveRecord::Transation` object.
 
     This allows to register callbacks on it.

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -680,7 +680,7 @@ module ActiveRecord
 
       def check_version # :nodoc:
         if database_version < "5.5.8"
-          raise "Your version of MySQL (#{database_version}) is too old. Active Record supports MySQL >= 5.5.8."
+          raise DatabaseVersionError, "Your version of MySQL (#{database_version}) is too old. Active Record supports MySQL >= 5.5.8."
         end
       end
 
@@ -1023,7 +1023,11 @@ module ActiveRecord
         end
 
         def version_string(full_version_string)
-          full_version_string.match(/^(?:5\.5\.5-)?(\d+\.\d+\.\d+)/)[1]
+          if full_version_string && matches = full_version_string.match(/^(?:5\.5\.5-)?(\d+\.\d+\.\d+)/)
+            matches[1]
+          else
+            raise DatabaseVersionError, "Unable to parse MySQL version from #{full_version_string.inspect}"
+          end
         end
     end
   end

activerecord/lib/active_record/errors.rb

@@ -575,4 +575,9 @@ module ActiveRecord
   # values, such as request parameters or model attributes to query methods.
   class UnknownAttributeReference < ActiveRecordError
   end
+
+  # DatabaseVersionError will be raised when the database version is not supported, or when
+  # the database version cannot be determined.
+  class DatabaseVersionError < ActiveRecordError
+  end
 end

activerecord/test/cases/adapters/abstract_mysql_adapter/connection_test.rb

@@ -216,6 +216,39 @@ class ConnectionTest < ActiveRecord::AbstractMysqlTestCase
       "expected release_advisory_lock to return false when there was no lock to release"
   end
 
+  def test_version_string
+    @connection.stub(:get_full_version, "8.0.35-0ubuntu0.22.04.1") do
+      assert_equal "8.0.35", @connection.get_database_version.to_s
+    end
+
+    @connection.stub(:get_full_version, "5.7.0") do
+      assert_equal "5.7.0", @connection.get_database_version.to_s
+    end
+  end
+
+  def test_version_string_invalid
+    @connection.stub(:get_full_version, "some-database-proxy") do
+      error = assert_raises(ActiveRecord::DatabaseVersionError) do
+        @connection.get_database_version
+      end
+      assert_equal "Unable to parse MySQL version from \"some-database-proxy\"", error.message
+    end
+
+    @connection.stub(:get_full_version, "") do
+      error = assert_raises(ActiveRecord::DatabaseVersionError) do
+        @connection.get_database_version
+      end
+      assert_equal "Unable to parse MySQL version from \"\"", error.message
+    end
+
+    @connection.stub(:get_full_version, nil) do
+      error = assert_raises(ActiveRecord::DatabaseVersionError) do
+        @connection.get_database_version
+      end
+      assert_equal "Unable to parse MySQL version from nil", error.message
+    end
+  end
+
   private
     def cause_server_side_disconnect
       @connection.update("set @@wait_timeout=1")