sql: more driver docs & tests; no functional changes

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5415055

src/pkg/exp/sql/driver/driver.go

@@ -94,12 +94,35 @@ type Result interface {
 // used by multiple goroutines concurrently.
 type Stmt interface {
 	// Close closes the statement.
+	//
+	// Closing a statement should not interrupt any outstanding
+	// query created from that statement. That is, the following
+	// order of operations is valid:
+	//
+	//  * create a driver statement
+	//  * call Query on statement, returning Rows
+	//  * close the statement
+	//  * read from Rows
+	//
+	// If closing a statement invalidates currently-running
+	// queries, the final step above will incorrectly fail.
+	//
+	// TODO(bradfitz): possibly remove the restriction above, if
+	// enough driver authors object and find it complicates their
+	// code too much. The sql package could be smarter about
+	// refcounting the statement and closing it at the appropriate
+	// time.
 	Close() error
 
 	// NumInput returns the number of placeholder parameters.
-	// -1 means the driver doesn't know how to count the number of
-	// placeholders, so we won't sanity check input here and instead let the
-	// driver deal with errors.
+	//
+	// If NumInput returns >= 0, the sql package will sanity check
+	// argument counts from callers and return errors to the caller
+	// before the statement's Exec or Query methods are called.
+	//
+	// NumInput may also return -1, if the driver doesn't know
+	// its number of placeholders. In that case, the sql package
+	// will not sanity check Exec or Query argument counts.
 	NumInput() int
 
 	// Exec executes a query that doesn't return rows, such

src/pkg/exp/sql/fakedb_test.go

@@ -90,6 +90,8 @@ type fakeStmt struct {
 	cmd   string
 	table string
 
+	closed bool
+
 	colName      []string      // used by CREATE, INSERT, SELECT (selected columns)
 	colType      []string      // used by CREATE
 	colValue     []interface{} // used by INSERT (mix of strings and "?" for bound params)
@@ -232,6 +234,9 @@ func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (driver.Stmt, e
 	stmt.table = parts[0]
 	stmt.colName = strings.Split(parts[1], ",")
 	for n, colspec := range strings.Split(parts[2], ",") {
+		if colspec == "" {
+			continue
+		}
 		nameVal := strings.Split(colspec, "=")
 		if len(nameVal) != 2 {
 			return nil, errf("SELECT on table %q has invalid column spec of %q (index %d)", stmt.table, colspec, n)
@@ -342,10 +347,16 @@ func (s *fakeStmt) ColumnConverter(idx int) driver.ValueConverter {
 }
 
 func (s *fakeStmt) Close() error {
+	s.closed = true
 	return nil
 }
 
+var errClosed = errors.New("fakedb: statement has been closed")
+
 func (s *fakeStmt) Exec(args []interface{}) (driver.Result, error) {
+	if s.closed {
+		return nil, errClosed
+	}
 	err := checkSubsetTypes(args)
 	if err != nil {
 		return nil, err
@@ -405,6 +416,9 @@ func (s *fakeStmt) execInsert(args []interface{}) (driver.Result, error) {
 }
 
 func (s *fakeStmt) Query(args []interface{}) (driver.Rows, error) {
+	if s.closed {
+		return nil, errClosed
+	}
 	err := checkSubsetTypes(args)
 	if err != nil {
 		return nil, err

src/pkg/exp/sql/sql_test.go

@@ -5,6 +5,7 @@
 package sql
 
 import (
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -22,7 +23,6 @@ func newTestDB(t *testing.T, name string) *DB {
 		exec(t, db, "INSERT|people|name=Alice,age=?", 1)
 		exec(t, db, "INSERT|people|name=Bob,age=?", 2)
 		exec(t, db, "INSERT|people|name=Chris,age=?", 3)
-
 	}
 	return db
 }
@@ -42,6 +42,40 @@ func closeDB(t *testing.T, db *DB) {
 }
 
 func TestQuery(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	rows, err := db.Query("SELECT|people|age,name|")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	type row struct {
+		age  int
+		name string
+	}
+	got := []row{}
+	for rows.Next() {
+		var r row
+		err = rows.Scan(&r.age, &r.name)
+		if err != nil {
+			t.Fatalf("Scan: %v", err)
+		}
+		got = append(got, r)
+	}
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("Err: %v", err)
+	}
+	want := []row{
+		{age: 1, name: "Alice"},
+		{age: 2, name: "Bob"},
+		{age: 3, name: "Chris"},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Logf(" got: %#v\nwant: %#v", got, want)
+	}
+}
+
+func TestQueryRow(t *testing.T) {
 	db := newTestDB(t, "people")
 	defer closeDB(t, db)
 	var name string
@@ -75,6 +109,24 @@ func TestQuery(t *testing.T) {
 	}
 }
 
+func TestStatementErrorAfterClose(t *testing.T) {
+	db := newTestDB(t, "people")
+	defer closeDB(t, db)
+	stmt, err := db.Prepare("SELECT|people|age|name=?")
+	if err != nil {
+		t.Fatalf("Prepare: %v", err)
+	}
+	err = stmt.Close()
+	if err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+	var name string
+	err = stmt.QueryRow("foo").Scan(&name)
+	if err == nil {
+		t.Errorf("expected error from QueryRow.Scan after Stmt.Close")
+	}
+}
+
 func TestStatementQueryRow(t *testing.T) {
 	db := newTestDB(t, "people")
 	defer closeDB(t, db)