More specific exception classes (#911)

* Simplify Mysql2::Error construction
* Implement more specific exception classes
* Raise specialized exception for connection and timeout errors

Author: casperisfine

ext/mysql2/client.c

@@ -15,7 +15,7 @@
 #include "mysql_enc_name_to_ruby.h"
 
 VALUE cMysql2Client;
-extern VALUE mMysql2, cMysql2Error;
+extern VALUE mMysql2, cMysql2Error, cMysql2TimeoutError;
 static VALUE sym_id, sym_version, sym_header_version, sym_async, sym_symbolize_keys, sym_as, sym_array, sym_stream;
 static VALUE sym_no_good_index_used, sym_no_index_used, sym_query_was_slow;
 static ID intern_brackets, intern_merge, intern_merge_bang, intern_new_with_args;
@@ -660,7 +660,7 @@ static VALUE do_query(void *args) {
     retval = rb_wait_for_single_fd(async_args->fd, RB_WAITFD_IN, tvp);
 
     if (retval == 0) {
-      rb_raise(cMysql2Error, "Timeout waiting for a response from the last query. (waited %d seconds)", FIX2INT(read_timeout));
+      rb_raise(cMysql2TimeoutError, "Timeout waiting for a response from the last query. (waited %d seconds)", FIX2INT(read_timeout));
     }
 
     if (retval < 0) {

ext/mysql2/mysql2_ext.c

@@ -1,11 +1,12 @@
 #include <mysql2_ext.h>
 
-VALUE mMysql2, cMysql2Error;
+VALUE mMysql2, cMysql2Error, cMysql2TimeoutError;
 
 /* Ruby Extension initializer */
 void Init_mysql2() {
   mMysql2      = rb_define_module("Mysql2");
   cMysql2Error = rb_const_get(mMysql2, rb_intern("Error"));
+  cMysql2TimeoutError = rb_const_get(cMysql2Error, rb_intern("TimeoutError"));
 
   init_mysql2_client();
   init_mysql2_result();

ext/mysql2/statement.c

@@ -1,7 +1,7 @@
 #include <mysql2_ext.h>
 
 VALUE cMysql2Statement;
-extern VALUE mMysql2, cMysql2Error, cBigDecimal, cDateTime, cDate;
+extern VALUE mMysql2, cMysql2Error, cMysql2TimeoutError, cBigDecimal, cDateTime, cDate;
 static VALUE sym_stream, intern_new_with_args, intern_each, intern_to_s, intern_merge_bang;
 static VALUE intern_sec_fraction, intern_usec, intern_sec, intern_min, intern_hour, intern_day, intern_month, intern_year;
 

lib/mysql2/error.rb

@@ -6,25 +6,60 @@ class Error < StandardError
       replace: '?'.freeze,
     }.freeze
 
+    ConnectionError = Class.new(Error)
+    TimeoutError = Class.new(Error)
+
+    CODES = {
+      1205 => TimeoutError, # ER_LOCK_WAIT_TIMEOUT
+
+      1044 => ConnectionError, # ER_DBACCESS_DENIED_ERROR
+      1045 => ConnectionError, # ER_ACCESS_DENIED_ERROR
+      1152 => ConnectionError, # ER_ABORTING_CONNECTION
+      1153 => ConnectionError, # ER_NET_PACKET_TOO_LARGE
+      1154 => ConnectionError, # ER_NET_READ_ERROR_FROM_PIPE
+      1155 => ConnectionError, # ER_NET_FCNTL_ERROR
+      1156 => ConnectionError, # ER_NET_PACKETS_OUT_OF_ORDER
+      1157 => ConnectionError, # ER_NET_UNCOMPRESS_ERROR
+      1158 => ConnectionError, # ER_NET_READ_ERROR
+      1159 => ConnectionError, # ER_NET_READ_INTERRUPTED
+      1160 => ConnectionError, # ER_NET_ERROR_ON_WRITE
+      1161 => ConnectionError, # ER_NET_WRITE_INTERRUPTED
+
+      2001 => ConnectionError, # CR_SOCKET_CREATE_ERROR
+      2002 => ConnectionError, # CR_CONNECTION_ERROR
+      2003 => ConnectionError, # CR_CONN_HOST_ERROR
+      2004 => ConnectionError, # CR_IPSOCK_ERROR
+      2005 => ConnectionError, # CR_UNKNOWN_HOST
+      2006 => ConnectionError, # CR_SERVER_GONE_ERROR
+      2007 => ConnectionError, # CR_VERSION_ERROR
+      2009 => ConnectionError, # CR_WRONG_HOST_INFO
+      2012 => ConnectionError, # CR_SERVER_HANDSHAKE_ERR
+      2013 => ConnectionError, # CR_SERVER_LOST
+      2020 => ConnectionError, # CR_NET_PACKET_TOO_LARGE
+      2026 => ConnectionError, # CR_SSL_CONNECTION_ERROR
+      2027 => ConnectionError, # CR_MALFORMED_PACKET
+      2047 => ConnectionError, # CR_CONN_UNKNOW_PROTOCOL
+      2048 => ConnectionError, # CR_INVALID_CONN_HANDLE
+      2049 => ConnectionError, # CR_UNUSED_1
+    }.freeze
+
     attr_reader :error_number, :sql_state
 
     # Mysql gem compatibility
     alias errno error_number
     alias error message
 
-    def initialize(msg)
-      @server_version ||= nil
+    def initialize(msg, server_version = nil, error_number = nil, sql_state = nil)
+      @server_version = server_version
+      @error_number = error_number
+      @sql_state = sql_state ? sql_state.encode(ENCODE_OPTS) : nil
 
       super(clean_message(msg))
     end
 
     def self.new_with_args(msg, server_version, error_number, sql_state)
-      err = allocate
-      err.instance_variable_set('@server_version', server_version)
-      err.instance_variable_set('@error_number', error_number)
-      err.instance_variable_set('@sql_state', sql_state.encode(ENCODE_OPTS))
-      err.send(:initialize, msg)
-      err
+      error_class = CODES.fetch(error_number, self)
+      error_class.new(msg, server_version, error_number, sql_state)
     end
 
     private

spec/mysql2/client_spec.rb

@@ -17,12 +17,12 @@
     end
   end
 
-  it "should raise an exception upon connection failure" do
+  it "should raise a Mysql::Error::ConnectionError 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::ConnectionError)
   end
 
   it "should raise an exception on create for invalid encodings" do
@@ -559,7 +559,7 @@ def run_gc
         client = new_client(read_timeout: 0)
         expect do
           client.query('SELECT SLEEP(0.1)')
-        end.to raise_error(Mysql2::Error)
+        end.to raise_error(Mysql2::Error::TimeoutError)
       end
 
       # XXX this test is not deterministic (because Unix signal handling is not)
@@ -918,10 +918,10 @@ def run_gc
     end
   end
 
-  it "should raise a Mysql2::Error exception upon connection failure" do
+  it "should raise a Mysql2::Error::ConnectionError exception upon connection failure due to invalid credentials" do
     expect do
-      new_client(host: "localhost", username: 'asdfasdf8d2h', password: 'asdfasdfw42')
-    end.to raise_error(Mysql2::Error)
+      new_client(host: 'localhost', username: 'asdfasdf8d2h', password: 'asdfasdfw42')
+    end.to raise_error(Mysql2::Error::ConnectionError)
 
     expect do
       new_client(DatabaseCredentials['root'])