email.template_value_invalid: An email template writes out a value that isn't text, a number or an enum with wording, such as a date

An email template writes out a value that isn't text, a number or an enum with wording, such as a date.

Area 16, Built-in services; not declinable; the next step is usually the agent's.

Why Jadpo refuses it

A template writes out only text, numbers and enums whose values have wording, because each of those has one way to be shown. A date, an amount of money or a list has many: a date needs a time zone, a language and a format before a person can read it. Jadpo won't pick them for you, so the template says how to show the value, and the error says how to do it for the type you wrote.

What it looks like

The welcome email writes out when the person joined, an Instant.

domains/accounts/emails/welcome_email.jadpo:

example

/// Sent once someone signs up.type WelcomeEmail = EmailMessage {    name: Text    joined_at: Instant}

domains/accounts/emails/welcome_email.html:

example

<p>Welcome, {{ name }}. You joined on {{ joined_at }}.</p>

jadpo checkcheck failed: 1 error, 3 files

error {{ joined_at }} can't be written out

--> domains/accounts/emails/welcome_email.html:1:42

  |1 | <p>Welcome, {{ name }}. You joined on {{ joined_at }}.</p>  |                                          ^^^^^^^^^ this is `Instant`

reason: A template writes out text (Text, PresentationText, or a type built on one), a number (Int or Decimal), or an enum whose values have wording, and Html as it is; joined_at is Instant.
next: Format it with text.format(...) (area 19), which writes it in the email's locale (agent)
rule: email.template_value_invalid
help: https://jadpo.dev/docs/errors/email.template_value_invalid

(agent) at the end of the next: line means your coding agent can make the fix itself.

How to fix it

If the value is a date, a time or an amount, format it with text.format, which writes it in the email's locale. A time also needs the zone to show it in, which the email is given as a field, and a format. In domains/accounts/emails/welcome_email.jadpo:

example

    zone: Zone

Then the template formats the time. In domains/accounts/emails/welcome_email.html:

text

<p>Welcome, {{ name }}. You joined on {{ text.format(joined_at, zone: zone, format: TimeFormat.date_long) }}.</p>

The email shows the date in the reader's zone, the way its locale writes it, such as "27 September 2026" in Locale.en_gb.

Other values have their own way to be shown. Use a Bool as the condition of an {{ if }}, walk a list with {{ for }}, write an object's fields out one by one, and give an enum's values wording.

Why Jadpo refuses it

What it looks like

How to fix it

Related