[19.0][ADD] product_uom_factor: product-specific UoM conversion

product_uom_factor/README.rst

@@ -0,0 +1,116 @@
+.. image:: https://odoo-community.org/readme-banner-image
+   :target: https://odoo-community.org/get-involved?utm_source=readme
+   :alt: Odoo Community Association
+
+=============================
+Product UoM Conversion Factor
+=============================
+
+.. 
+   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+   !! This file is generated by oca-gen-addon-readme !!
+   !! changes will be overwritten.                   !!
+   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+   !! source digest: sha256:e4fc656789bb785888bc779bf2be3607062c97ce46ee17bc1b09cc5d34999203
+   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+.. |badge1| image:: https://img.shields.io/badge/maturity-Alpha-red.png
+    :target: https://odoo-community.org/page/development-status
+    :alt: Alpha
+.. |badge2| image:: https://img.shields.io/badge/license-LGPL--3-blue.png
+    :target: http://www.gnu.org/licenses/lgpl-3.0-standalone.html
+    :alt: License: LGPL-3
+.. |badge3| image:: https://img.shields.io/badge/github-OCA%2Fproduct--attribute-lightgray.png?logo=github
+    :target: https://github.com/OCA/product-attribute/tree/19.0/product_uom_factor
+    :alt: OCA/product-attribute
+.. |badge4| image:: https://img.shields.io/badge/weblate-Translate%20me-F47D42.png
+    :target: https://translation.odoo-community.org/projects/product-attribute-19-0/product-attribute-19-0-product_uom_factor
+    :alt: Translate me on Weblate
+.. |badge5| image:: https://img.shields.io/badge/runboat-Try%20me-875A7B.png
+    :target: https://runboat.odoo-community.org/builds?repo=OCA/product-attribute&target_branch=19.0
+    :alt: Try me on Runboat
+
+|badge1| |badge2| |badge3| |badge4| |badge5|
+
+Odoo 19.0 allows adding UoMs from any category to a product's
+"Packagings" (``uom_ids`` field), enabling users to sell or purchase in
+units from a different category than the product's base UoM (e.g.,
+selling ink by the liter when it is stocked by weight in grams).
+
+However, Odoo's ``_compute_quantity()`` and ``_compute_price()`` methods
+on ``uom.uom`` no longer enforce that the source and destination UoMs
+belong to the same category. When converting between UoMs of different
+categories, the conversion silently produces incorrect results —
+typically a 1:1 ratio between base units of their respective categories
+— because the standard UoM factor is relative to the category's
+reference unit, not to the product.
+
+This module adds a **conversion factor** field to the ``product.uom``
+model (the per-product/per-UoM link table). This factor represents the
+product-specific relationship between the product's base UoM and the
+cross-category UoM. For example, an ink product stocked in grams with a
+density of 1.05 g/mL would have a factor of 1.05 on its liter packaging
+UoM, meaning 1 liter = 1050 grams.
+
+The module overrides ``_compute_quantity()`` and ``_compute_price()`` so
+that when a product is available in context, cross-category conversions
+use the product-specific factor instead of producing potentially
+incoherent results.
+
+.. IMPORTANT::
+   This is an alpha version, the data model and design can change at any time without warning.
+   Only for development or testing purpose, do not use in production.
+   `More details on development status <https://odoo-community.org/page/development-status>`_
+
+**Table of contents**
+
+.. contents::
+   :local:
+
+Bug Tracker
+===========
+
+Bugs are tracked on `GitHub Issues <https://github.com/OCA/product-attribute/issues>`_.
+In case of trouble, please check there if your issue has already been reported.
+If you spotted it first, help us to smash it by providing a detailed and welcomed
+`feedback <https://github.com/OCA/product-attribute/issues/new?body=module:%20product_uom_factor%0Aversion:%2019.0%0A%0A**Steps%20to%20reproduce**%0A-%20...%0A%0A**Current%20behavior**%0A%0A**Expected%20behavior**>`_.
+
+Do not contact contributors directly about support or help with technical issues.
+
+Credits
+=======
+
+Authors
+-------
+
+* Bemade Inc.
+
+Contributors
+------------
+
+- Marc Durepos marc@bemade.org, Bemade Inc.
+
+Maintainers
+-----------
+
+This module is maintained by the OCA.
+
+.. image:: https://odoo-community.org/logo.png
+   :alt: Odoo Community Association
+   :target: https://odoo-community.org
+
+OCA, or the Odoo Community Association, is a nonprofit organization whose
+mission is to support the collaborative development of Odoo features and
+promote its widespread use.
+
+.. |maintainer-mdurepos| image:: https://github.com/mdurepos.png?size=40px
+    :target: https://github.com/mdurepos
+    :alt: mdurepos
+
+Current `maintainer <https://odoo-community.org/page/maintainer-role>`__:
+
+|maintainer-mdurepos| 
+
+This module is part of the `OCA/product-attribute <https://github.com/OCA/product-attribute/tree/19.0/product_uom_factor>`_ project on GitHub.
+
+You are welcome to contribute. To learn how please visit https://odoo-community.org/page/Contribute.

product_uom_factor/__init__.py

@@ -0,0 +1 @@
+from . import models

product_uom_factor/__manifest__.py

@@ -0,0 +1,21 @@
+# Copyright 2026 Bemade Inc.
+# License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl).
+
+{
+    "name": "Product UoM Conversion Factor",
+    "summary": "Product-specific conversion factors for cross-category UoM conversions",
+    "version": "19.0.1.0.0",
+    "development_status": "Alpha",
+    "license": "LGPL-3",
+    "author": "Bemade Inc., Odoo Community Association (OCA)",
+    "website": "https://github.com/OCA/product-attribute",
+    "maintainers": ["mdurepos"],
+    "depends": [
+        "product",
+    ],
+    "data": [
+        "security/ir.model.access.csv",
+        "views/product_product_views.xml",
+        "views/product_template_views.xml",
+    ],
+}

product_uom_factor/models/__init__.py

@@ -0,0 +1,4 @@
+from . import product_product
+from . import product_template
+from . import product_uom_factor
+from . import uom_uom

product_uom_factor/models/product_product.py

@@ -0,0 +1,26 @@
+from odoo import fields, models
+
+
+class ProductProduct(models.Model):
+    _inherit = "product.product"
+
+    uom_factor_ids = fields.Many2many(
+        "product.uom.factor",
+        string="UoM Conversion Factors",
+        compute="_compute_uom_factor_ids",
+    )
+
+    def _compute_uom_factor_ids(self):
+        Factor = self.env["product.uom.factor"]
+        for product in self:
+            if not product.id or not product.product_tmpl_id.id:
+                product.uom_factor_ids = Factor
+                continue
+            product.uom_factor_ids = Factor.search(
+                [
+                    ("product_tmpl_id", "=", product.product_tmpl_id.id),
+                    "|",
+                    ("product_ids", "=", False),
+                    ("product_ids", "in", product.id),
+                ]
+            )

product_uom_factor/models/product_template.py

@@ -0,0 +1,67 @@
+from odoo import api, fields, models
+
+
+class ProductTemplate(models.Model):
+    _inherit = "product.template"
+
+    uom_factor_ids = fields.One2many(
+        "product.uom.factor",
+        "product_tmpl_id",
+        string="UoM Conversion Factors",
+    )
+
+    def write(self, vals):
+        res = super().write(vals)
+        if "uom_ids" in vals:
+            self._sync_uom_factor_ids()
+        return res
+
+    def _sync_uom_factor_ids(self):
+        Factor = self.env["product.uom.factor"]
+        for template in self:
+            base_uom = template.uom_id
+            cross_uoms = template.uom_ids.filtered(
+                lambda u, bu=base_uom: not bu._has_common_reference(u)
+            )
+            existing = template.uom_factor_ids
+            # Create missing factors for cross-category UoMs
+            existing_uom_ids = existing.mapped("uom_id")
+            for uom in cross_uoms - existing_uom_ids:
+                Factor.create(
+                    {
+                        "product_tmpl_id": template.id,
+                        "uom_id": uom.id,
+                    }
+                )
+            # Delete factors whose UoM was removed from uom_ids
+            to_delete = existing.filtered(lambda f, cu=cross_uoms: f.uom_id not in cu)
+            to_delete.unlink()
+
+    @api.constrains("uom_factor_ids")
+    def _check_uom_factor_coverage(self):
+        """Ensure variant coverage for each cross-category UoM.
+        Auto-cleans duplicate catch-all lines and auto-creates missing
+        catch-alls when not all variants are explicitly covered.
+        Uses uom_ids (the template's allowed UoMs) as the source of truth
+        for which UoMs need coverage, not just existing factor lines."""
+        Factor = self.env["product.uom.factor"]
+        for template in self:
+            base_uom = template.uom_id
+            cross_uoms = template.uom_ids.filtered(
+                lambda u, bu=base_uom: not bu._has_common_reference(u)
+            )
+            for uom in cross_uoms:
+                siblings = template.uom_factor_ids.filtered(
+                    lambda f, u=uom: f.uom_id == u
+                )
+                # Auto-create catch-all if needed
+                catchalls = siblings.filtered(lambda f: not f.product_ids)
+                if not catchalls:
+                    covered = siblings.mapped("product_ids")
+                    if covered != template.product_variant_ids:
+                        Factor.create(
+                            {
+                                "product_tmpl_id": template.id,
+                                "uom_id": uom.id,
+                            }
+                        )

product_uom_factor/models/product_uom_factor.py

@@ -0,0 +1,105 @@
+from odoo import api, fields, models
+from odoo.exceptions import ValidationError
+
+
+class ProductUomFactor(models.Model):
+    _name = "product.uom.factor"
+    _description = "Product-specific UoM Conversion Factor"
+
+    product_tmpl_id = fields.Many2one(
+        "product.template",
+        string="Product Template",
+        required=True,
+        readonly=True,
+        index=True,
+        ondelete="cascade",
+    )
+    product_ids = fields.Many2many(
+        "product.product",
+        string="Variants",
+        help="Specific variants this factor applies to. "
+        "Leave empty to apply to all variants.",
+    )
+    uom_id = fields.Many2one(
+        "uom.uom",
+        "Unit of Measure",
+        required=True,
+        readonly=True,
+        index=True,
+        ondelete="cascade",
+    )
+    factor = fields.Float(
+        "Conversion Factor",
+        default=1.0,
+        required=True,
+        help="Product-specific conversion factor for cross-category UoM "
+        "conversions. Represents how many of the product's base UoM equal "
+        "one unit of this UoM. For example, for ink with a specific "
+        "gravity of 1.05 and base UoM of grams, the factor on the mL "
+        "UoM would be 1.05 (1 mL = 1.05 g).",
+    )
+
+    def write(self, vals):
+        res = super().write(vals)
+        if "product_ids" in vals:
+            self.mapped("product_tmpl_id")._check_uom_factor_coverage()
+        return res
+
+    def unlink(self):
+        templates = self.mapped("product_tmpl_id")
+        res = super().unlink()
+        templates._check_uom_factor_coverage()
+        return res
+
+    @api.constrains("product_ids", "product_tmpl_id")
+    def _check_product_ids_same_template(self):
+        for rec in self:
+            if rec.product_ids and any(
+                p.product_tmpl_id != rec.product_tmpl_id for p in rec.product_ids
+            ):
+                raise ValidationError(
+                    self.env._("All variants must belong to the same product template.")
+                )
+
+    @api.constrains("product_ids", "uom_id", "product_tmpl_id")
+    def _check_no_duplicate_factors(self):
+        """Auto-clean duplicate factor lines, then raise if any remain.
+        A duplicate is defined as two records with the same
+        (uom_id, product_tmpl_id, frozenset(product_ids))."""
+        tmpl_uom_pairs = {(rec.product_tmpl_id.id, rec.uom_id.id) for rec in self}
+        for tmpl_id, uom_id in tmpl_uom_pairs:
+            siblings = self.search(
+                [
+                    ("product_tmpl_id", "=", tmpl_id),
+                    ("uom_id", "=", uom_id),
+                ]
+            )
+            keys = []
+            to_delete = self.browse()
+            for sib in siblings:
+                key = (uom_id, tmpl_id, frozenset(sib.product_ids.ids))
+                if key in keys:
+                    to_delete |= sib
+                else:
+                    keys.append(key)
+            if to_delete:
+                to_delete.unlink()
+
+    @api.constrains("factor", "uom_id", "product_tmpl_id")
+    def _check_same_category_factor(self):
+        for rec in self:
+            base_uom = rec.product_tmpl_id.uom_id
+            if base_uom._has_common_reference(rec.uom_id):
+                expected = rec.uom_id.factor / base_uom.factor
+                if rec.factor != expected:
+                    raise ValidationError(
+                        self.env._(
+                            "The conversion factor for %(uom)s cannot be "
+                            "customized because it is in the same category "
+                            "as the product's base UoM (%(base_uom)s). "
+                            "Expected factor: %(expected)s.",
+                            uom=rec.uom_id.name,
+                            base_uom=base_uom.name,
+                            expected=expected,
+                        )
+                    )