pol_product_many2one

Buying a product that comes in sizes and colors is a different task from buying one that does not. On a purchase order, entering twelve variants as twelve lines is slow and error prone, and a grid is the obvious answer.

This widget decides which of the two situations you are in. On selecting a product it asks the server whether that product resolves to a single variant. If it does, the line is filled and you carry on.

If it does not, the grid configurator opens instead, quantities are entered per variant, and the lines are generated from the grid.

Purchasing teams that deal in apparel, hardware or anything else with a size and color axis lose real time to variant entry, and the errors it produces surface later as receiving discrepancies. A matrix is one of the highest-return configurations in Odoo Purchase for those businesses.

The thing to check is that the variant structure actually matches how you buy. A matrix on the wrong two attributes is worse than no matrix, because it makes the wrong entry the fastest one.

The usual usage

<field name="product_template_id"
       widget="pol_product_many2one"/>

The field is the template; the widget resolves it to a variant or opens the grid.

What the server is asked

get_single_product_variant()
# returns a variant id when there is exactly one
# otherwise the grid configurator opens

The browser never counts variants itself.

Without the matrix

<field name="product_id" widget="many2one"/>

One variant per line, entered by hand.

The interesting part is where the decision is made. Selecting a product triggers a server call asking whether that template resolves to a single variant, and the answer drives everything after.

Doing that server side rather than counting variants in the browser is what makes it correct in the awkward cases. Attribute exclusion rules can reduce a template with three attributes to a single sellable variant, and only the server knows that.

When the answer is a single variant, the widget sets it and the line behaves like any other. When it is not, the grid opens and the quantities entered there generate the lines rather than the field setting one.

Everything else, the dropdown, the search, the creation paths, is inherited from the many-to-one field unchanged, which is why the file is short.

Odoo 20 is expected at Odoo Experience in Brussels, 24 to 26 September 2026. The development branch is unstable and this may still change; we re-verify this page after the release.

Byte-identical. The file on the development branch matches Odoo 19 exactly, including the single variant call.