Fixing allowing Named Instances, adding it as an option (#13)

* adding a docker instance that tests mssqlex with custom ports

* don't forget to build custom port container

* allow for named instances + ports with new opts. tests for both

* simplify and fix travis docker tests

* oops, wrong port number

* updating docs to reflect options changes

docker-compose.yml

@@ -5,15 +5,18 @@ services:
     environment:
       - ACCEPT_EULA=Y
       - SA_PASSWORD=TestPa$$word123
+      - MSSQL_TCP_PORT=9204
 
   mssqlex:
     build: .
     environment:
       - MIX_ENV=test
       - MSSQL_UID=sa
       - MSSQL_PWD=TestPa$$word123
-      - MSSQL_HST=tcp:sql_server,1433
+      - MSSQL_HST=sql_server
+      - MSSQL_IN=MSSQLSERVER
+      - MSSQL_PRT=9204
       - TRAVIS_JOB_ID=$TRAVIS_JOB_ID
     depends_on:
       - sql_server
-    command: ["./wait-for-it.sh", "sql_server:1433", "-s", "--", "mix", "coveralls.travis"]
+    command: ["./wait-for-it.sh", "sql_server:9204", "-s", "--", "mix", "coveralls.travis"]

lib/mssqlex.ex

@@ -15,14 +15,22 @@ defmodule Mssqlex do
 
   `opts` expects a keyword list with zero or more of:
 
-    * `:odbc_driver` - The driver the adapter will use
-      (default: {ODBC Driver 13 for SQL Server})
-    * `:hostname` - The server hostname (default: localhost)
-    * `:port` - The server port number (default: 1433)
-    * `:database` - The name of the database
-      (default: MSSQL_DB environment variable)
-    * `:username` - Username (default: MSSQL_UID environment variable)
-    * `:password` - User password (default: MSSQL_PWD environment variable)
+    * `:odbc_driver` - The driver the adapter will use.
+        * environment variable: `MSSQL_DVR`
+        * default value: {ODBC Driver 13 for SQL Server}
+    * `:hostname` - The server hostname.
+        * environment variable: `MSSQL_HST`
+        * default value: localhost
+    * `:instance_name` - OPTIONAL. The name of the instance, if using named instances.
+        * environment variable: `MSSQL_IN`
+    * `:port` - OPTIONAL. The server port number.
+        * environment variable: `MSSQL_PRT`
+    * `:database` - The name of the database.
+        * environment variable: `MSSQL_DB`
+    * `:username` - Username.
+        * environment variable: `MSSQL_UID`
+    * `:password` - User's password.
+        * environment variable: `MSSQL_PWD`
 
   `Mssqlex` uses the `DBConnection` framework and supports all `DBConnection`
   options like `:idle`, `:after_connect` etc.

lib/mssqlex/protocol.ex

@@ -40,10 +40,15 @@ defmodule Mssqlex.Protocol do
   @spec connect(opts :: Keyword.t) :: {:ok, state}
                                     | {:error, Exception.t}
   def connect(opts) do
+
+    server_address = opts[:hostname] || System.get_env("MSSQL_HST") || "localhost"
+    instance_name = opts[:instance_name] || System.get_env("MSSQL_IN")
+    port = opts[:port] || System.get_env("MSSQL_PRT")
+
     conn_opts = [
-      {"DRIVER", opts[:odbc_driver] || "{ODBC Driver 13 for SQL Server}"},
-      {"SERVER", (opts[:hostname] || System.get_env("MSSQL_HST") || "localhost") <> "," <> (opts[:port] || "1433")},
-      {"DATABASE", opts[:database] || System.get_env("MSSQL_DB")},
+      {"Driver", opts[:odbc_driver] || System.get_env("MSSQL_DVR") || "{ODBC Driver 13 for SQL Server}"},
+      {"Server", build_server_address(server_address, instance_name, port)},
+      {"Database", opts[:database] || System.get_env("MSSQL_DB")},
       {"UID", opts[:username] || System.get_env("MSSQL_UID")},
       {"PWD", opts[:password] || System.get_env("MSSQL_PWD")}
     ]
@@ -62,6 +67,14 @@ defmodule Mssqlex.Protocol do
     end
   end
 
+  @spec build_server_address(String.t, String.t, String.t) :: String.t
+  defp build_server_address(server_address, instance_name, port)
+
+  defp build_server_address(server_address, nil, nil), do: server_address
+  defp build_server_address(server_address, instance_name, nil), do: "#{server_address}\\#{instance_name}"
+  defp build_server_address(server_address, nil, port), do: "#{server_address},#{port}"
+  defp build_server_address(server_address, instance_name, port), do: "#{server_address}\\#{instance_name},#{port}"
+
   @doc false
   @spec disconnect(err :: Exception.t, state) :: :ok
   def disconnect(_err, %{pid: pid} = state) do