go/zodb: tests: Provide way to commit IPersistent objects

Add a way for tests to serialize and commit IPersistent objects. The
commit, for now, is implemented via calling external zodbtools/py to
commit raw data (see 7f14e2cb "go/zodb/fs1: tests: Factor-out commiting
a transaction via ZODB/py into common place). The data to commit is what
object serialization (see previous patch) gives.

For now there is no tracking of dirtiness. A test must explicitly list
objects it wants to save into database.

This functionality will soon be used to implement Persistent/DB/...
tests.

go/zodb/impexp_test.go

+// Copyright (C) 2019  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+package zodb
+
+import (
+	"lab.nexedi.com/kirr/go123/mem"
+)
+
+// imported at runtime via import_x_test due to cyclic dependency:
+
+var ZPyCommit func(string, Tid, ...IPersistent) (Tid, error)
+
+// exported for zodb_test package:
+
+func PSerialize(obj IPersistent) *mem.Buf {
+	return obj.persistent().pSerialize()
+}

go/zodb/import_x_test.go

+// Copyright (C) 2019  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+package zodb_test
+
+import (
+	"lab.nexedi.com/kirr/go123/mem"
+	"lab.nexedi.com/kirr/neo/go/zodb"
+	"lab.nexedi.com/kirr/neo/go/internal/xtesting"
+
+	// we need file:// support in ZODB tests.
+	// wks or any other storage cannot be imported from zodb due to cycle.
+	_ "lab.nexedi.com/kirr/neo/go/zodb/storage/fs1"
+)
+
+// import at runtime few things into zodb tests, that zodb cannot import itself
+// due to cyclic dependency.
+
+func init() {
+	zodb.ZPyCommit = ZPyCommit
+}
+
+// ZPyCommit commits new transaction with specified objects.
+//
+// The objects need to be alive, but do not need to be marked as changed.
+// The commit is performed via zodb/py.
+func ZPyCommit(zurl string, at zodb.Tid, objv ...zodb.IPersistent) (zodb.Tid, error) {
+	var rawobjv []xtesting.ZRawObject // raw zodb objects data to commit
+	var bufv []*mem.Buf               // buffers to release
+	defer func() {
+		for _, buf := range bufv {
+			buf.Release()
+		}
+	}()
+
+	for _, obj := range objv {
+		buf := zodb.PSerialize(obj)
+		rawobj := xtesting.ZRawObject{
+			Oid:  obj.POid(),
+			Data: buf.Data,
+		}
+		rawobjv = append(rawobjv, rawobj)
+		bufv = append(bufv, buf)
+	}
+
+	return xtesting.ZPyCommitRaw(zurl, at, rawobjv...)
+}