add auto @fields resolver in finder

Author: mekramy

mysql/repo_find.go

@@ -4,6 +4,7 @@ import (
 "context"
 "database/sql"
 "errors"
+"strings"
 
 "github.com/georgysavva/scany/v2/sqlscan"
 )
@@ -21,6 +22,7 @@ type Finder[T any] interface {
 WithTransformer(func(*T) error) Finder[T]
 
 // Rows executes the query and returns a pgx.Rows iterator for processing result rows.
+// Auto replace @fields with struct fields list
 Rows(ctx context.Context, args ...any) (*sql.Rows, error)
 
 // Struct executes the query and retrieves a single result, or an error if the query fails.
@@ -67,7 +69,16 @@ func (f *finder[T]) Rows(ctx context.Context, args ...any) (*sql.Rows, error) {
 return nil, ErrEmptySQL
 }
 
-cmd := compile(f.sql, f.replacements...)
+replacements := append([]string{}, f.replacements...)
+if columns := typeColumns[T]([]string{}, []string{}); len(columns) > 0 {
+replacements = append(
+replacements,
+"@fields",
+strings.Join(columns, ","),
+)
+}
+
+cmd := compile(f.sql, replacements...)
 rows, err := f.db.QueryContext(ctx, cmd, args...)
 
 if errors.Is(err, sql.ErrNoRows) {

mysql/utils.go

@@ -53,6 +53,12 @@ func structColumns(v any, only, exclude []string) []string {
 return columns
 }
 
+// typeColumns extracts column names from the `db` struct tag from type
+func typeColumns[T any](only, exclude []string) []string {
+var v T
+return structColumns(v, only, exclude)
+}
+
 // structValues extracts field values from a struct based on the `db` tag, excluding unexported fields.
 func structValues(v any, only, exclude []string) []any {
 val := reflect.Indirect(reflect.ValueOf(v))

postgres/repo_find.go

@@ -3,6 +3,7 @@ package postgres
 import (
 "context"
 "errors"
+"strings"
 
 "github.com/jackc/pgx/v5"
 )
@@ -20,6 +21,7 @@ type Finder[T any] interface {
 WithTransformer(func(*T) error) Finder[T]
 
 // Rows executes the query and returns a pgx.Rows iterator for processing result rows.
+// Auto replace @fields with struct fields list
 Rows(ctx context.Context, args ...any) (pgx.Rows, error)
 
 // Struct executes the query and retrieves a single result, or an error if the query fails.
@@ -66,7 +68,16 @@ func (f *finder[T]) Rows(ctx context.Context, args ...any) (pgx.Rows, error) {
 return nil, ErrEmptySQL
 }
 
-sql := compile(f.sql, f.replacements...)
+replacements := append([]string{}, f.replacements...)
+if columns := typeColumns[T]([]string{}, []string{}); len(columns) > 0 {
+replacements = append(
+replacements,
+"@fields",
+strings.Join(columns, ","),
+)
+}
+
+sql := compile(f.sql, replacements...)
 rows, err := f.db.Query(ctx, sql, args...)
 
 if errors.Is(err, pgx.ErrNoRows) {

postgres/utils.go

@@ -53,6 +53,12 @@ func structColumns(v any, only, exclude []string) []string {
 return columns
 }
 
+// typeColumns extracts column names from the `db` struct tag from type
+func typeColumns[T any](only, exclude []string) []string {
+var v T
+return structColumns(v, only, exclude)
+}
+
 // structValues extracts field values from a struct based on the `db` tag, excluding unexported fields.
 func structValues(v any, only, exclude []string) []any {
 val := reflect.Indirect(reflect.ValueOf(v))