Implement more specific exception classes

Author: byroot

lib/mysql2/error.rb

@@ -8,6 +8,13 @@ class Error < StandardError
       replace: '?'.freeze,
     }.freeze
 
+    BaseConnectionError = Class.new(Error)
+
+    CODES = {
+      1045 => AccessDenied = Class.new(BaseConnectionError),
+      2005 => UnknownHost = Class.new(BaseConnectionError),
+    }
+
     attr_reader :error_number, :sql_state
 
     # Mysql gem compatibility
@@ -23,7 +30,8 @@ def initialize(msg, server_version = nil, error_number = nil, sql_state = nil)
     end
 
     def self.new_with_args(msg, server_version, error_number, sql_state)
-      new(msg, server_version, error_number, sql_state)
+      error_class = CODES.fetch(error_number, self)
+      error_class.new(msg, server_version, error_number, sql_state)
     end
 
     private

spec/mysql2/client_spec.rb

@@ -19,12 +19,12 @@
     end
   end
 
-  it "should raise an exception upon connection failure" do
+  it "should raise a Mysql::Error::UnknownHost upon connection failure" do
     expect do
       # The odd local host IP address forces the mysql client library to
       # use a TCP socket rather than a domain socket.
       new_client('host' => '127.0.0.2', 'port' => 999999)
-    end.to raise_error(Mysql2::Error)
+    end.to raise_error(Mysql2::Error::UnknownHost)
   end
 
   it "should raise an exception on create for invalid encodings" do
@@ -924,10 +924,10 @@ def run_gc
     end
   end
 
-  it "should raise a Mysql2::Error exception upon connection failure" do
-    expect do
-      new_client(host: "localhost", username: 'asdfasdf8d2h', password: 'asdfasdfw42')
-    end.to raise_error(Mysql2::Error)
+  it "should raise a Mysql2::Error::AccessDenied exception upon connection failure due to invalid credentials" do
+    expect {
+      new_client(:host => "localhost", :username => 'asdfasdf8d2h', :password => 'asdfasdfw42')
+    }.to raise_error(Mysql2::Error::AccessDenied)
 
     expect do
       new_client(DatabaseCredentials['root'])