[IMP] snippets: preserve same file module

In `make_pickleable_callback`, when creating a name for the module created via
import_script, no longer make the name random, but derive it from the script's
path deterministically via a hash function. This way, when this method is
called multiple times from the same script for multiple callbacks, it will only
import the script once and otherwise re-use the created module. This ensures
multiple callbacks from the same script file will run within the same module,
seeing e.g. the same values in modified globals, which is much more intuitive.

Also, move the function to `misc.py`. With the intention to reuse it, it's a
better fit. For that, make it python2 compatible.

closes #295

Related: odoo/upgrade#8047
Signed-off-by: Christophe Simonis (chs) <chs@odoo.com>

Author: cawo-odoo

src/util/misc.py

@@ -4,9 +4,12 @@
 import collections
 import datetime
 import functools
+import hashlib
+import inspect
 import logging
 import os
 import re
+import sys
 import textwrap
 import uuid
 from contextlib import contextmanager
@@ -21,7 +24,7 @@
     from openerp.modules.module import get_module_path
     from openerp.tools.parse_version import parse_version
 
-from .exceptions import SleepyDeveloperError
+from .exceptions import MigrationError, SleepyDeveloperError
 
 # python3 shim
 try:
@@ -391,6 +394,31 @@ def log(chunk_num, size=chunk_size):
         log(i // chunk_size + 1, i % chunk_size)
 
 
+def make_pickleable_callback(callback):
+    """
+    Make a callable importable.
+
+    `ProcessPoolExecutor.map` arguments needs to be pickleable
+    Functions can only be pickled if they are importable.
+    However, the callback's file is not importable due to the dash in the filename.
+    We should then put the executed function in its own importable file.
+
+    :meta private: exclude from online docs
+    """
+    callback_filepath = inspect.getfile(callback)
+    name = "_upgrade_" + hashlib.sha256(callback_filepath.encode()).hexdigest()
+    if name not in sys.modules:
+        sys.modules[name] = import_script(callback_filepath, name=name)
+    try:
+        return getattr(sys.modules[name], callback.__name__)
+    except AttributeError:
+        error_msg = (
+            "The converter callback `{}` is a nested function in `{}`.\n"
+            "Move it outside the `migrate()` function to make it top-level."
+        ).format(callback.__name__, callback.__module__)
+        raise MigrationError(error_msg)
+
+
 class SelfPrint(object):
     """
     Class that will return a self representing string. Used to evaluate domains.

src/util/snippets.py

@@ -1,9 +1,6 @@
 # -*- coding: utf-8 -*-
-import inspect
 import logging
 import re
-import sys
-import uuid
 from concurrent.futures import ProcessPoolExecutor
 
 from lxml import etree, html
@@ -12,9 +9,8 @@
 from psycopg2.extras import Json
 
 from .const import NEARLYWARN
-from .exceptions import MigrationError
 from .helpers import table_of_model
-from .misc import import_script, log_progress
+from .misc import log_progress, make_pickleable_callback
 from .pg import column_exists, column_type, get_max_workers, table_exists
 
 _logger = logging.getLogger(__name__)
@@ -161,28 +157,6 @@ def html_converter(transform_callback, selector=None):
     return HTMLConverter(make_pickleable_callback(transform_callback), selector)
 
 
-def make_pickleable_callback(callback):
-    """
-    Make a callable importable.
-
-    `ProcessPoolExecutor.map` arguments needs to be pickleable
-    Functions can only be pickled if they are importable.
-    However, the callback's file is not importable due to the dash in the filename.
-    We should then put the executed function in its own importable file.
-    """
-    callback_filepath = inspect.getfile(callback)
-    name = f"_upgrade_{uuid.uuid4().hex}"
-    mod = sys.modules[name] = import_script(callback_filepath, name=name)
-    try:
-        return getattr(mod, callback.__name__)
-    except AttributeError:
-        error_msg = (
-            f"The converter callback `{callback.__name__}` is a nested function in `{callback.__module__}`.\n"
-            "Move it outside the `migrate()` function to make it top-level."
-        )
-        raise MigrationError(error_msg) from None
-
-
 class BaseConverter:
     def __init__(self, callback, selector=None):
         self.callback = callback