Add http status code translations for errors

Errors will now have their status codes set based on the error
message returned by the MySQL driver.

lib/mysql.js

@@ -16,6 +16,7 @@ var ParameterizedSQL = SqlConnector.ParameterizedSQL;
 var EnumFactory = require('./enumFactory').EnumFactory;
 
 var debug = require('debug')('loopback:connector:mysql');
+var setHttpCode = require('./set-http-code');
 
 /**
  * @module loopback-connector-mysql
@@ -186,6 +187,9 @@ MySQL.prototype.executeSQL = function(sql, params, options, callback) {
     if (!transaction) {
       connection.release();
     }
+    if (err) {
+      err = setHttpCode(err);
+    }
     callback && callback(err, result);
   }
 

lib/set-http-code.js

@@ -0,0 +1,45 @@
+// Copyright IBM Corp. 2012,2017. All Rights Reserved.
+// Node module: loopback-connector-mysql
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var _ = require('lodash');
+
+var codes = {
+  '404': [
+    'ER_DB_DROP_EXISTS',
+    'ER_BAD_TABLE_ERROR',
+  ],
+  '422': [
+    'ER_DUP_ENTRY',
+    'ER_CANT_CREATE_DB',
+    'ER_DB_CREATE_EXISTS',
+    'ER_TABLE_EXISTS_ERROR',
+  ],
+};
+
+/*!
+ * Translate MySQL error codes into HTTP Errors.
+ * If an error would be better represented by a code that isn't 500,
+ * add your SQL error to the correct HTTP code array above!
+ */
+module.exports = function(err) {
+  if (!err) {
+    return;
+  } else if (!(err instanceof Error)) {
+    err = new Error(err); // Sucks that we weren't given an error object...
+  }
+  // Find error prefix
+  var msg = err.message;
+  var sqlError = msg.substring(0, msg.indexOf(':'));
+
+  for (var code in codes) {
+    if (_.includes(codes[code], sqlError)) {
+      err.statusCode = code;
+    }
+  }
+  if (!err.statusCode) err.statusCode = 500;
+  return err;
+};

test/set-http-code.test.js

@@ -0,0 +1,43 @@
+// Copyright IBM Corp. 2012,2017. All Rights Reserved.
+// Node module: loopback-connector-mysql
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var setHttpCode = require('../lib/set-http-code');
+var should = require('./init.js');
+
+describe('setHttpCode', function() {
+  describe('should set statusCode', function() {
+    testErrorCode('404 on db not found', 'ER_DB_DROP_EXISTS: Nope', 404);
+    testErrorCode('404 on table not found', 'ER_BAD_TABLE_ERROR: Nope', 404);
+
+    testErrorCode('422 on duplicates', 'ER_DUP_ENTRY: Duplicate entry', 422);
+    testErrorCode('422 on cannot create db', 'ER_CANT_CREATE_DB: Oops', 422);
+    testErrorCode('422 on db already exists', 'ER_DB_CREATE_EXISTS: Oops', 422);
+    testErrorCode('422 on db not found', 'ER_TABLE_EXISTS_ERROR: Nope', 422);
+
+    testErrorCode('500 on unknown errors', 'FATAL: Sadness happened', 500);
+
+    function testErrorCode(name, msg, expected) {
+      it(name, function() {
+        var err = new Error(msg);
+        err = setHttpCode(err);
+        should.exist(err.statusCode);
+        should.equal(err.statusCode, expected);
+      });
+    }
+  });
+  it('should do nothing without error', function() {
+    should.doesNotThrow(setHttpCode);
+  });
+
+  it('should convert strings to errors', function() {
+    var err = 'REALLY_BAD: Something truly awful occurred.';
+    err = setHttpCode(err);
+    should.exist(err.statusCode);
+    should(err instanceof Error);
+    should.equal(err.statusCode, 500);
+  });
+});