fix(table): populate caller records on multi-record Insert (#24)

table.go

@@ -132,7 +132,15 @@ func (t *Table[T, P, I]) insertAll(ctx context.Context, records []P) error {
 	for start := 0; start < len(records); start += chunkSize {
 		end := min(start+chunkSize, len(records))
 
+		// Preserve the original pointers: GetAll resets the slice and appends
+		// freshly scanned structs, so it only reflects back to the caller when
+		// they spread a slice. Copy the DB-returned values into the originals so
+		// caller records receive generated ids/defaults regardless of how they
+		// called Insert (same behaviour as insertOne/GetOne and Save).
 		chunk := records[start:end]
+		originals := make([]P, len(chunk))
+		copy(originals, chunk)
+
 		q := t.SQL.
 			InsertRecords(chunk).
 			Into(t.Name).
@@ -141,6 +149,11 @@ func (t *Table[T, P, I]) insertAll(ctx context.Context, records []P) error {
 		if err := t.Query.GetAll(ctx, q, &chunk); err != nil {
 			return fmt.Errorf("insert records: %w", err)
 		}
+
+		for i, rr := range chunk {
+			*originals[i] = *rr
+			records[start+i] = originals[i]
+		}
 	}
 
 	return nil

tests/issue24_repro_test.go

@@ -0,0 +1,43 @@
+package pgkit_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestInsertMultiPopulatesRecords_Issue24 covers
+// https://github.com/goware/pgkit/issues/24: a batch insert where some records
+// set the ,omitempty created_at and some leave it zero.
+//
+// Two guarantees:
+//  1. It must not fail with SQLSTATE 42601 (VALUES lists of differing length) —
+//     the row that skips created_at falls back to the column DEFAULT.
+//  2. Every caller record must receive its DB-generated id and defaults, the
+//     same as a single Insert and as Save. Passing records as individual
+//     variadic args (not a spread slice) is the path that did not populate back.
+func TestInsertMultiPopulatesRecords_Issue24(t *testing.T) {
+	truncateTable(t, "accounts")
+	ctx := context.Background()
+	db := initDB(DB)
+
+	fixed := time.Date(2020, 1, 2, 3, 4, 5, 0, time.UTC)
+	withTime := &Account{Name: "with-created-at", CreatedAt: fixed}
+	withoutTime := &Account{Name: "default-created-at"} // created_at zero -> omitempty -> DEFAULT
+
+	err := db.Accounts.Insert(ctx, withTime, withoutTime)
+	require.NoError(t, err, "batch insert with mixed ,omitempty created_at")
+
+	require.NotZero(t, withTime.ID, "id populated on caller record")
+	require.NotZero(t, withoutTime.ID, "id populated on caller record")
+	assert.True(t, withTime.CreatedAt.Equal(fixed), "explicit created_at preserved")
+	assert.False(t, withoutTime.CreatedAt.IsZero(), "skipped created_at filled by DB DEFAULT")
+
+	// The rows actually landed and are addressable by their generated ids.
+	got, err := db.Accounts.GetByID(ctx, withoutTime.ID)
+	require.NoError(t, err)
+	assert.Equal(t, "default-created-at", got.Name)
+}