E0086: interpolation_format_spec

E0086 interpolation_format_spec — a format spec in an interpolation (use format()).

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0086).

The rule

Soma interpolations take no format spec, so {total:.2f} would print literally; check refuses it. Format the value with a builtin: {to_fixed(total, 2)}, or let s = format("%.2f", total) and then {s}.

A program that triggers it

cell Receipt {
    on summary(customer: String, total: Float) {
        return "{customer} owes {total:.2f} EUR"
    }
}

What soma check prints:

$ soma check wrong.cell
error: string interpolation `{total:.2f}` has a Python format spec — Soma has none, so it would print literally; format the value: `{to_fixed(total, 2)}` (printf-style: `let s = format("%.2f", total)`, then `{s}`)
  --> wrong.cell:3:16
  |
3 |         return "{customer} owes {total:.2f} EUR"
  |                ^
  = code: E0086
✗ 1 error(s), 0 warning(s).

The fix field of soma check --json: Soma has none, so it would print literally; format the value: `{to_fixed(total, 2)}` (printf-style: `let s = format("%.2f", total)`, then `{s}`)

The fix

On line 3, return "{customer} owes {total:.2f} EUR" becomes return "{customer} owes {to_fixed(total, 2)} EUR".

--- wrong.cell
+++ right.cell
@@ -1,5 +1,5 @@
 cell Receipt {
     on summary(customer: String, total: Float) {
-        return "{customer} owes {total:.2f} EUR"
+        return "{customer} owes {to_fixed(total, 2)} EUR"
     }
 }

With the fix, soma check accepts the program:

$ soma check right.cell
✓ All checks passed.