(core) ensure randomness works when sandbox is cloned from a checkpoint

Summary:
This calls a new `initialize` method on the sandbox before we start
doing calculations with it, to make sure that `random.seed()` has
been called. Otherwise, if the sandbox is cloned from a checkpoint,
the seed will have been reset.

The `initialize` method includes the functionality previously done
by `set_doc_url` since it is also initialization/personalization and
this way we avoid introducing another round trip to the sandbox.

Test Plan: tested with grist-core configured to use gvisor

Reviewers: georgegevoian, dsagal

Reviewed By: georgegevoian, dsagal

Subscribers: alexmojaki

Differential Revision: https://phab.getgrist.com/D3549

app/server/lib/ActiveDoc.ts

@@ -2059,9 +2059,7 @@ export class ActiveDoc extends EventEmitter {
         num_on_demand_tables: onDemandNames.length,
       });
 
-      if (this._options?.docUrl) {
-        await this._pyCall('set_doc_url', this._options.docUrl);
-      }
+      await this._pyCall('initialize', this._options?.docUrl);
 
       // Calculations are not associated specifically with the user opening the document.
       // TODO: be careful with which users can create formulas.

sandbox/grist/functions/math.py

@@ -15,10 +15,6 @@ from functions.info import ISNUMBER, ISLOGICAL
 from functions.unimplemented import unimplemented
 import roman
 
-if os.environ.get("DETERMINISTIC_MODE"):
-  random.seed(1)
-
-
 # Iterates through elements of iterable arguments, or through individual args when not iterable.
 def _chain(*values_or_iterables):
   for v in values_or_iterables:

sandbox/grist/main.py

@@ -3,6 +3,7 @@ This module defines what sandbox functions are made available to the Node contro
 and starts the grist sandbox. See engine.py for the API documentation.
 """
 import os
+import random
 import sys
 sys.path.append('thirdparty')
 # pylint: disable=wrong-import-position
@@ -121,8 +122,14 @@ def run(sandbox):
     return schema.SCHEMA_VERSION
 
   @export
-  def set_doc_url(doc_url):
-    os.environ['DOC_URL'] = doc_url
+  def initialize(doc_url):
+    if os.environ.get("DETERMINISTIC_MODE"):
+      random.seed(1)
+    else:
+      # Make sure we have randomness, even if we are being cloned from a checkpoint
+      random.seed()
+    if doc_url:
+      os.environ['DOC_URL'] = doc_url
 
   @export
   def get_formula_error(table_id, col_id, row_id):