[FIX] base: render db manager w/ qweb and no db

Due to odoo#82724 and 8ec7739,
the qweb renderer can't be used directly, however there is no way to use
the proper ir.qweb one without a database.

This is necessary for the /web/database/ routes (db manager) which work
without a database, and require qweb rendering since the abandon of
jinja rendering in v15.

This patch builds on the preparation work of the qweb/ir_qweb merge in odoo#81024
which introduces a limited helper `render()` method in ir_qweb so that
it can be used statically without a database.

Fixes odoo#82835

closes odoo#82841

X-original-commit: 3014e92
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>
Signed-off-by: Olivier Dony <odo@odoo.com>

addons/web/controllers/main.py

@@ -31,7 +31,7 @@
 import odoo
 import odoo.modules.registry
 from odoo.api import call_kw
-from odoo.addons.base.models.qweb import QWeb
+from odoo.addons.base.models.ir_qweb import render as qweb_render
 from odoo.modules import get_resource_path, module, get_manifest
 from odoo.tools import html_escape, pycompat, ustr, apply_inheritance_specs, lazy_property, float_repr, osutil
 from odoo.tools.mimetypes import guess_mimetype
@@ -1082,7 +1082,7 @@ def _render_template(self, **d):
         def load(template_name, options):
             return (html.fragment_fromstring(templates[template_name]), template_name)
 
-        return QWeb()._render(html.document_fromstring(template), d, load=load)
+        return qweb_render(html.document_fromstring(template), d, load=load)
 
     @http.route('/web/database/selector', type='http', auth="none")
     def selector(self, **kw):

odoo/addons/base/models/ir_qweb.py

@@ -355,3 +355,43 @@ def _compile_expr(self, expr, raise_on_missing=False):
 
         assert_valid_codeobj(_SAFE_QWEB_OPCODES, compile(namespace_expr, '<>', 'eval'), expr)
         return namespace_expr
+
+
+def render(template_name, values, load, **options):
+    """ Rendering of a qweb template without database and outside the registry.
+    (Widget, field, or asset rendering is not implemented.)
+    :param (string|int) template_name: template identifier
+    :param dict values: template values to be used for rendering
+    :param def load: function like `load(template_name, options)` which
+        returns an etree from the given template name (from initial rendering
+        or template `t-call`).
+    :param options: used to compile the template (the dict available for the
+        rendering is frozen)
+    :returns: bytes marked as markup-safe (decode to :class:`markupsafe.Markup`
+                instead of `str`)
+    :rtype: MarkupSafe
+    """
+    class MockPool:
+        db_name = None
+        _Registry__cache = {}
+
+    class MockIrQWeb(IrQWeb):
+        pool = MockPool()
+
+        def _get_field(self, *args):
+            raise NotImplementedError("Fields are not allowed in this rendering mode. Please use \"env['ir.qweb']._render\" method")
+
+        def _get_widget(self, *args):
+            raise NotImplementedError("Widgets are not allowed in this rendering mode. Please use \"env['ir.qweb']._render\" method")
+
+        def _get_asset_nodes(self, *args):
+            raise NotImplementedError("Assets are not allowed in this rendering mode. Please use \"env['ir.qweb']._render\" method")
+
+    class MockEnv(dict):
+        def __init__(self):
+            super().__init__()
+            self.context = {}
+
+    renderer = object.__new__(MockIrQWeb)
+    renderer.env = MockEnv()
+    return renderer._render(template_name, values, load=load, **options)