database/sql: allow OpenConnector in a driver.Driver interface

While driver.Connector was previously added to allow non-string
connection arguments and access to the context, most users of
the sql package will continue to rely on a string DSN.

Allow drivers to implement a string DSN to Connector interface
that both allows a single parsing of the string DSN and uses
the Connector interface which passes available context to
the driver dialer.

Fixes #22713

Change-Id: Ia0b862262f4c4670effe2538d0d6d43733fea18d
Reviewed-on: https://go-review.googlesource.com/77550
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/database/sql/driver/driver.go b/src/database/sql/driver/driver.go
index b3f9d9c26c..b9bf19c04d 100644
--- a/src/database/sql/driver/driver.go
+++ b/src/database/sql/driver/driver.go
@@ -55,6 +55,17 @@ type Driver interface {
 	Open(name string) (Conn, error)
 }
 
+// DriverContext enhances the Driver interface by returning a Connector
+// rather then a single Conn.
+// It separates out the name parsing step from actually connecting to the
+// database. It also gives dialers access to the context by using the
+// Connector.
+type DriverContext interface {
+	// OpenConnector must parse the name in the same format that Driver.Open
+	// parses the name parameter.
+	OpenConnector(name string) (Connector, error)
+}
+
 // Connector is an optional interface that drivers can implement.
 // It allows drivers to provide more flexible methods to open
 // database connections without requiring the use of a DSN string.