PhoenixKitEcommerce.PriceDisplay (PhoenixKitEcommerce v0.2.0)

How a price is written on the storefront: From €40.00 /hour.

Two independent decorations, both optional and both off by default:

a unit — free text per language ("per hour", "/m²", "в час"), so a service shop can state its pricing model. Free text rather than a vocabulary: nothing here needs to know what an hour is, and every shop invents units the next one has never heard of.
a "From" prefix — set explicitly by the admin, or implied when the product's options genuinely produce a price range.

Storage

Both live under one reserved key in Product.metadata:

%{"_price_display" => %{
    "unit" => %{"en" => "per hour", "ru" => "в час"},
    "from" => true
  }}

A single versioned namespace rather than two loose top-level keys: the metadata map is an advertised extension point, so this module's data stays in one place that can grow (and be recognised) without colliding with whatever a host already stores there. _-prefixed matches the existing _option_values / _price_modifiers convention, and option keys may not begin with _, so no user-defined option can shadow it.

Context is load-bearing

render/4 takes a context because the same product means different things on different pages:

:catalog — the product's asking price. May show "From", and the amount comes from the product's option-aware range.
:selected — the price for the options the shopper picked. Exact, so never "From"; keeps the unit.
:cart / :order — a SNAPSHOT of what was (or will be) charged. Exact, never "From", and the unit comes from the snapshot rather than the live product, so an edit or deletion cannot rewrite a line the customer already agreed to.

Absent data renders exactly what the module rendered before this existed.

Summary

Functions

any_line_on_request?(lines)

Whether any line in a cart or order was agreed as "price on request".

build(unit_map, from?)

Builds the storable namespace map from admin form input.

build(unit_map, from?, on_request?)

line_on_request?(line)

Whether a stored LINE was agreed as "price on request".

metadata_key()

The reserved metadata key. Consumers that copy metadata around (the CSV upsert, the product form) use this to preserve the namespace.

on_request?(product_or_metadata)

Whether this product's price is negotiated rather than listed ("price on request" / "цена договорная").

render(product, currency, ctx, opts \\ [])

Renders a price for display.

settings(metadata)

Reads the display settings out of a product (or a raw metadata map).

unit_for(product_or_metadata, language)

The unit text for a language, with default-language fallback.

Functions

any_line_on_request?(lines)

Whether any line in a cart or order was agreed as "price on request".

Suppressing the amount per line leaves the TOTAL saying something the shop does not mean: an on-request line snapshots 0, so a cart holding one reads "Total 0.00" beside a "Proceed to Checkout" button, and a mixed cart quietly omits the on-request item from a figure the shopper reads as the whole bill. The totals themselves stay as they are — they are the amounts billing will charge — so the pages that show one disclose what it leaves out.

build(unit_map, from?)

Builds the storable namespace map from admin form input.

Blank units are dropped so an untouched form does not persist empty strings, and values are length-bounded — this text renders next to a price on a public page, it is not a description field.

build(unit_map, from?, on_request?)

line_on_request?(line)

Whether a stored LINE was agreed as "price on request".

This is the snapshot side of on_request?/1, and every page that renders a line must ask it rather than reading the live product. It accepts both shapes the storefront holds a line in: a CartItem (the flag lives under metadata) and an order line item (a plain map, flag at the top level).

A helper rather than the inline (item.metadata || %{})["price_on_request"] == true this replaces: five templates need the answer — cart, checkout review, the product page's "already in cart" notice, the confirmation and order details — and the two that expressed it inline were the two that got it, while the other three rendered 0.00 for a line with no price.