Add SQL message to error object

Changes.md

@@ -6,6 +6,7 @@ you spot any mistakes.
 
 ## HEAD
 
+* Add `sqlMessage` property to query `Error` objects [#1714](https://github.com/mysqljs/mysql/pull/1714)
 * Add `sql` property to query `Error` objects #1462 #1628 #1629
 * Update `bignumber.js` to 4.0.2
 * Update `readable-stream` to 2.2.9

Readme.md

@@ -1117,6 +1117,11 @@ object. Additionally they typically come with two extra properties:
 * `err.sql`: String, contains the full SQL of the failed query. This can be
   useful when using a higher level interface like an ORM that is generating
   the queries.
+* `err.sqlMessage`: String, contains the message associated with the current
+  SQL State of the database. For example, with
+  `SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "My Error"`, `err.sqlMessage`
+  would be set to `"My Error"`. When using triggers for data validation, this
+  can be used to pass error messages through from the database to the user.
 
 [Error]: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error
 [MySQL server error]: http://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html

lib/protocol/sequences/Sequence.js

@@ -53,6 +53,7 @@ Sequence.prototype._packetToError = function(packet) {
   err.code = code;
   err.errno = packet.errno;
   err.sqlState = packet.sqlState;
+  err.sqlMessage = packet.message;
 
   return err;
 };

test/integration/connection/test-error-message.js

@@ -0,0 +1,46 @@
+var assert = require('assert');
+var common = require('../../common');
+
+var table = 'error_message_test';
+var message = 'Name must not contain b.';
+
+common.getTestConnection(function (err, connection) {
+  assert.ifError(err);
+
+  common.useTestDb(connection);
+
+  // Must use real table because temporary tables cannot have triggers
+  connection.query([
+    'CREATE TABLE ?? (',
+    '`name` varchar(255)',
+    ') ENGINE=InnoDB DEFAULT CHARSET=utf8'
+  ].join('\n'), [table], assert.ifError);
+
+  // Create a trigger that throws error when name contains the letter "b"
+  connection.query([
+    'CREATE TRIGGER `validateName`',
+    'BEFORE INSERT ON ??',
+    'FOR EACH ROW BEGIN',
+    'IF (NEW.name like \'%b%\') THEN',
+    'SIGNAL SQLSTATE \'45000\' SET MESSAGE_TEXT = ?;',
+    'END IF;',
+    'END;'
+  ].join('\n'), [table, message], function (err) {
+    // Clean up table if create trigger fails
+    connection.query('DROP TABLE IF EXISTS ??', [table], assert.ifError);
+    assert.ifError(err);
+  });
+
+  // Violates trigger condition, so it will throw an error on insert
+  var row = ['bbbbbbbbbb'];
+
+  connection.query('INSERT INTO ?? (name) VALUES ?', [table, [row]], function (insertErr) {
+    // Remove table when insert finishes
+    connection.query('DROP TABLE IF EXISTS ??', [table], function (err) {
+      assert.ifError(err);
+      connection.end(assert.ifError);
+      assert.equal(insertErr.sqlMessage, message,
+                   'error sqlMessage property is the trigger error message');
+    });
+  });
+});