[IMP] server_environment: module uninstallation

Add a helper to manage the restoring of the database columns when a
module using `server_environment` is uninstalled or the dependency on
`server_environment` is dropped.

Document how to use the helper in an uninstall script or in an upgrade
script (if a new version of the addon drops the dependency).

Author: gurneyalex

server_environment/models/server_env_mixin.py

@@ -7,7 +7,7 @@
 from lxml import etree
 
 from odoo import api, fields, models
-from odoo.tools import mute_logger
+from odoo.tools import SQL, mute_logger, sql
 
 from odoo.addons.base_sparse_field.models.fields import Serialized
 
@@ -428,3 +428,70 @@ def _setup_base(self):
             self._server_env_transform_field_to_read_from_env(field)
             self._server_env_add_is_editable_field(field)
         return
+
+    @api.model
+    def restore_env_managed_columns(self, model_name, field_names):
+        """Restore database columns for fields formerly managed via server.env.mixin.
+
+        When an addon binds ``server.env.mixin`` to an existing model, the ORM
+        drops the original stored columns.  Call this helper from an
+        ``uninstall_hook`` so those columns are recreated and repopulated
+        with their current effective values before the addon is removed.
+
+        The hook must run *while* the module's ORM extensions are still active
+        (guaranteed by Odoo's uninstall sequence: hooks execute before
+        ``Module.module_uninstall()``), so the env-computed fields are still
+        readable and their values can be written back to freshly created columns.
+
+        The operation is idempotent: calling it multiple times will not fail.
+
+        :param str model_name: dotted model name, e.g. ``"ir.mail_server"``
+        :param field_names: iterable of field names whose columns to restore
+        """
+        model = self.env[model_name]
+        cr = self.env.cr
+        for field_name in field_names:
+            field = model._fields.get(field_name)
+            if field is None:
+                _logger.warning(
+                    "restore_env_managed_columns: field %r not found on %s, skipping",
+                    field_name,
+                    model_name,
+                )
+                continue
+            column_type = field.column_type
+            if column_type is None:
+                _logger.warning(
+                    "restore_env_managed_columns: "
+                    "field %r on %s has no SQL column type, skipping",
+                    field_name,
+                    model_name,
+                )
+                continue
+            table = model._table
+            if not sql.column_exists(cr, table, field_name):
+                sql.create_column(cr, table, field_name, column_type[1], field.string)
+                _logger.info(
+                    "restore_env_managed_columns: created column %s.%s (%s)",
+                    table,
+                    field_name,
+                    column_type[1],
+                )
+            # Repopulate every existing record with the current computed value.
+            # The hook runs while the ORM extensions are still active, so the
+            # env-computed field is still readable via the normal accessor.
+            for record in model.search([]):
+                value = record[field_name]
+                # The ORM returns False for NULL on non-boolean fields; map
+                # that back to None so psycopg2 writes a proper SQL NULL.
+                if value is False and field.type != "boolean":
+                    value = None
+                cr.execute(
+                    SQL(
+                        "UPDATE %s SET %s = %s WHERE id = %s",
+                        SQL.identifier(table),
+                        SQL.identifier(field_name),
+                        value,
+                        record.id,
+                    )
+                )

server_environment/readme/USAGE.md

@@ -19,3 +19,115 @@ If you want to have a technical name to reference:
         _inherit = ["storage.backend", "server.env.techname.mixin"]
 
         [...]
+
+## Restoring columns on uninstall
+
+When `server.env.mixin` is bound to an existing model, the ORM drops the
+original stored columns for all env-managed fields. If the binding addon is
+later uninstalled, those columns must be recreated so the database remains
+usable.
+
+Add an `uninstall_hook` to your addon and delegate to
+`restore_env_managed_columns`:
+
+    # your_addon/__init__.py
+    from . import models
+
+    def uninstall_hook(env):
+        env["server.env.mixin"].restore_env_managed_columns(
+            "storage.backend",
+            ["directory_path", "other_field"],
+        )
+
+    # your_addon/__manifest__.py
+    {
+        ...
+        "uninstall_hook": "uninstall_hook",
+    }
+
+The helper creates any missing columns (idempotent: safe to call multiple
+times) and repopulates them with each record's current effective value —
+whether that value came from an environment configuration file or from the
+stored default field (`x_<field>_env_default`).
+
+The hook must run *before* the ORM extensions are removed, which is guaranteed
+by Odoo's uninstall sequence (hooks execute before `Module.module_uninstall()`).
+
+## Migrating when dropping server_environment dependency
+
+When refactoring an existing addon that embeds a `server.env.mixin` binding, you
+may want to extract the binding into a separate *glue* addon and drop the
+`server_environment` dependency from the original.  This keeps the base addon
+lightweight while preserving server-environment features for those who install
+the glue addon.
+
+**Pattern:**
+
+- **Original addon (v1)**: depends on `server_environment` and binds the mixin
+  directly in model code.
+- **Refactored addon (v2)**: removes `server_environment` from dependencies,
+  removes the mixin binding and the related ORM model inheritance.
+- **New glue addon** (optional, same version): depends on both `server_environment`
+  and the original addon v2; re-adds the mixin binding in a separate module file.
+
+**Migration checklist:**
+
+1. In the **original addon's v2 `__manifest__.py`**:
+   - Remove `"server_environment"` from `depends`.
+   - Remove the model file(s) that contained the mixin binding.
+   - Update `depends` to add the new glue addon *if* the base addon still needs it
+     (otherwise, make the glue addon optional for users who want env-binding).
+
+2. In the **original addon's v2 model code**:
+   - Delete or simplify the model class that inherited from `server.env.mixin`.
+   - If the model was only there for the binding, remove it entirely.
+   - Restore the original field definitions (not as computed fields).
+
+3. **Create a migration script** (if needed) to restore columns *during the addon
+   upgrade*, before the ORM model extensions are unloaded.  Use a `@post_load`
+   hook or a dedicated migration script:
+
+       # migrations/18.0.1.0.0/post-restore-columns.py
+       def migrate(cr, version):
+           # Call the restoration logic while the v1 model is still active
+           env = odoo.api.Environment(cr, odoo.SUPERUSER_ID, {})
+           env["server.env.mixin"].restore_env_managed_columns(
+               "storage.backend",
+               ["directory_path", "other_field"],
+           )
+
+4. **Create the glue addon** with the model re-inheritance:
+
+       # your_addon_env/__init__.py
+       from . import models
+
+       # your_addon_env/models/__init__.py
+       from . import storage_backend
+
+       # your_addon_env/models/storage_backend.py
+       class StorageBackend(models.Model):
+           _name = "storage.backend"
+           _inherit = ["storage.backend", "server.env.mixin"]
+
+           @property
+           def _server_env_fields(self):
+               return {"directory_path": {}}
+
+       # your_addon_env/__manifest__.py
+       {
+           "name": "Storage Backend – Server Environment",
+           "version": "18.0.1.0.0",
+           "depends": ["server_environment", "storage_backend"],
+           "installable": True,
+       }
+
+**Key points:**
+
+- Column restoration must happen *during the addon upgrade* (step 3), not as an
+  uninstall hook, because the original model binding is still active.
+- The `restore_env_managed_columns` helper is idempotent and safe to call even
+  if columns already exist.
+- Users who do not need server environment features simply do *not* install the
+  glue addon—the base addon continues to work with plain database columns.
+- Users who do need server environment can install both the base addon (v2+) and
+  the glue addon (same version) to get the binding back.

server_environment/tests/test_server_environment.py

@@ -146,3 +146,14 @@ def test_server_environment_disabled_overwrite_options_section_by_env(self):
         with self.set_config_dir("testfiles"):
             server_env._load_config()
             self.assertEqual(odoo_config["odoo_test_option"], "fake odoo config")
+
+        def test_restore_env_managed_columns_unknown_field(self):
+            """Helper gracefully skips a field that doesn't exist on the model."""
+            # Must not raise even when the field name doesn't exist.
+            self.env["server.env.mixin"].restore_env_managed_columns(
+                "res.partner", ["__nonexistent_field_xyz__"]
+            )
+
+        def test_restore_env_managed_columns_no_fields(self):
+            """Helper is a no-op when given an empty field list."""
+            self.env["server.env.mixin"].restore_env_managed_columns("res.partner", [])