W0003: unknown_property

W0003 unknown_property — a slot property nothing defines.

A warning of soma check, the checker of the Soma programming language (soma explain W0003).

The rule

A memory slot's properties in [...] must be ones Soma or a loaded cell property defines; an unknown name is not an error, but it does nothing, and soma check warns with W0003 and suggests the closest known property. A misspelled [persistant] therefore leaves the slot without the persistence the programmer meant. Correct the spelling ([persistent]), or define the property with cell property persistant { } if it really is your own.

A program that triggers it

cell Inventory {
    memory {
        stock: Map<String, Int> [persistant]
    }
    on restock(sku: String, qty: Int) {
        let next = (stock.get(sku) ?? 0) + qty
        stock.set(sku, next)
        return next
    }
}

What soma check prints:

$ soma check wrong.cell
warning: unknown property 'persistant' on 'stock' — did you mean 'persistent'? (it is not defined in any loaded cell property, so it does nothing)
  --> wrong.cell:3:34
  |
3 |         stock: Map<String, Int> [persistant]
  |                                  ^
✓ 1 warning(s), no errors.

The fix field of soma check --json: Write 'persistent' on slot 'stock', or, if 'persistant' is a property of your own, define it with 'cell property persistant { }'.

The fix

On line 3, stock: Map<String, Int> [persistant] becomes stock: Map<String, Int> [persistent].

--- wrong.cell
+++ right.cell
@@ -1,5 +1,5 @@
 cell Inventory {
     memory {
-        stock: Map<String, Int> [persistant]
+        stock: Map<String, Int> [persistent]
     }
     on restock(sku: String, qty: Int) {

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.