db can query 1 level nested dotnotation

src/db/db.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"fmt"
+	"strings"
 )
 
 func QueryOne[T any](ctx context.Context, q string, args ...any) (T, error) {
@@ -33,12 +34,33 @@ func Query[T any](ctx context.Context, q string, args ...any) ([]T, error) {
 	}
 	scanners := func(columns []string) ([]any, error) {
 		s := make([]any, len(columns))
-		for i, k := range columns {
-			v, ok := m[k]
-			if !ok {
-				return nil, fmt.Errorf("cannot scan column %s to %T (%+v)", k, a, m)
+		i := 0
+		for i < len(columns) {
+			k := columns[i]
+			if strings.Contains(k, ".") {
+				columns := strings.SplitN(k, ".", 2)
+				m2, ok := m[columns[0]]
+				if !ok {
+					return nil, fmt.Errorf("no column %s in %T (%+v)", columns[0], a, m)
+				}
+				m3, ok := m2.(map[string]any)
+				if !ok {
+					return nil, fmt.Errorf("cannot scan subfield %s of %s of %T (%+v)", columns[1], columns[0], a, m)
+				}
+				v, ok := m3[columns[1]]
+				if !ok {
+					return nil, fmt.Errorf("no subfield %s of %s of %T (%+v)", columns[1], columns[0], a, m)
+				}
+				s[i] = &v
+				i += 1
+			} else {
+				v, ok := m[k]
+				if !ok {
+					return nil, fmt.Errorf("no column %s in %T (%+v)", k, a, m)
+				}
+				s[i] = &v
+				i += 1
 			}
-			s[i] = &v
 		}
 		return s, nil
 	}
@@ -67,7 +89,21 @@ func Query[T any](ctx context.Context, q string, args ...any) ([]T, error) {
 
 			m := map[string]any{}
 			for i, column := range columns {
-				m[column] = scanners[i]
+				if !strings.Contains(column, ".") {
+					m[column] = scanners[i]
+				} else {
+					columns := strings.SplitN(column, ".", 2)
+					m2, ok := m[columns[0]]
+					if !ok {
+						m2 = map[string]any{}
+					}
+					m3, ok := m2.(map[string]any)
+					if !ok {
+						return fmt.Errorf("%s is not a submap", columns[0])
+					}
+					m3[columns[1]] = scanners[i]
+					m[columns[0]] = m3
+				}
 			}
 
 			var a T

src/db/db_test.go

@@ -46,4 +46,15 @@ func TestDB(t *testing.T) {
 	} else if gots[1].K != "b" {
 		t.Errorf("expected [1]='b' but got %q", gots[1].K)
 	}
+
+	type NestedResult struct {
+		Nest struct {
+			K string `json:"k"`
+		}
+	}
+	if got, err := db.QueryOne[NestedResult](ctx, `SELECT k AS "Nest.k" FROM test WHERE k='a'`); err != nil {
+		t.Errorf("failed nested query one: %v", err)
+	} else if got.Nest.K != "a" {
+		t.Errorf("bad nested query one: %+v", got)
+	}
 }