From 0e8f00e11c89c8d1adcd6d0aba5ee4c6a74cfcb1 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Thu, 11 Apr 2013 20:22:55 -0500
Subject: [PATCH] Added understanding of error messages from server

---
 conn.go      | 21 +++++++++++++++++++++
 conn_test.go |  7 +++++++
 messages.go  | 11 +++++++++++
 3 files changed, 39 insertions(+)

diff --git a/conn.go b/conn.go
index 40c5174f..95011782 100644
--- a/conn.go
+++ b/conn.go
@@ -132,6 +132,8 @@ func (c *conn) processContextFreeMsg(t byte, r *messageReader) (err error) {
 	case 'S':
 		c.rxParameterStatus(r)
 		return nil
+	case errorResponse:
+		return c.rxErrorResponse(r)
 	default:
 		return fmt.Errorf("Received unknown message type: %c", t)
 	}
@@ -190,6 +192,25 @@ func (c *conn) rxParameterStatus(r *messageReader) {
 	c.runtimeParams[key] = value
 }
 
+func (c *conn) rxErrorResponse(r *messageReader) (err PgError) {
+	for {
+		switch r.readByte() {
+		case 'S':
+			err.Severity = r.readString()
+		case 'C':
+			err.Code = r.readString()
+		case 'M':
+			err.Message = r.readString()
+		case 0: // End of error message
+			return
+		default: // Ignore other error fields
+			r.readString();
+		}
+	}
+
+	panic("Unreachable")
+}
+
 func (c *conn) rxBackendKeyData(r *messageReader) {
 	c.pid = r.readInt32()
 	c.secretKey = r.readInt32()
diff --git a/conn_test.go b/conn_test.go
index 1ce520f9..48f82b17 100644
--- a/conn_test.go
+++ b/conn_test.go
@@ -34,6 +34,13 @@ func TestConnect(t *testing.T) {
 	}
 }
 
+func TestConnectWithInvalidUser(t *testing.T) {
+	_, err := Connect(map[string]string{"socket": "/private/tmp/.s.PGSQL.5432", "user": "invalid_user", "database": "pgx_test"})
+	pgErr := err.(PgError)
+	if pgErr.Code != "28000" {
+		t.Fatal("Did not receive expected error when connecting with invalid user")
+	}
+}
 func TestQuery(t *testing.T) {
 	conn, err := Connect(map[string]string{"socket": "/private/tmp/.s.PGSQL.5432", "user": "pgx", "database": "pgx_test"})
 	if err != nil {
diff --git a/messages.go b/messages.go
index bbc145fc..349e4e09 100644
--- a/messages.go
+++ b/messages.go
@@ -15,6 +15,7 @@ const (
 	rowDescription  = 'T'
 	dataRow         = 'D'
 	commandComplete = 'C'
+	errorResponse = 'E'
 )
 
 type startupMessage struct {
@@ -50,3 +51,13 @@ type fieldDescription struct {
 	modifier        int32
 	formatCode      int16
 }
+
+type PgError struct {
+	Severity string
+	Code string
+	Message string
+}
+
+func (self PgError) Error() string {
+	return self.Severity + ": " + self.Message + " (SQLSTATE " + self.Code + ")"
+}