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replace {{#if}} with Mustachio scoped sections and inverted groups #3

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replace {{#if}} with Mustachio scoped sections and inverted groups #3

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48 changes: 33 additions & 15 deletions postmark-templates/references/handlebars-syntax.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
# Handlebars Template Syntax

Postmark templates use Handlebars (Mustache-compatible) syntax. Templates are rendered server-side — no client-side library needed.
Postmark templates use **Mustachio** — a Mustache-based templating language with a few extra capabilities. Templates are rendered server-side — no client-side library needed.

## Variables

Expand All @@ -26,28 +26,45 @@ Use triple braces to render raw HTML without escaping:

## Conditionals

Postmark uses **Mustachio** templating, which does not support `{{#if}}`. Instead, conditionals work via scoped sections and inverted groups.

### Truthy block (value exists and is not falsy)

```handlebars
{{#if premium_member}}
{{#premium_member}}
<p>Thank you for being a premium member!</p>
{{else}}
<p>Upgrade to premium for exclusive benefits.</p>
{{/if}}
{{/premium_member}}
```

Falsy values (`false`, `0`, `""`, `null`, `undefined`, `[]`) trigger the `else` branch.
The block is skipped if `premium_member` is `false`, `null`, `0`, `""`, or missing.

### Inverted group (value is absent or falsy)

Use `{{^property}}` to render content when a value is absent or falsy — the Mustachio equivalent of `else`:

```handlebars
{{#premium_member}}
<p>Thank you for being a premium member!</p>
{{/premium_member}}
{{^premium_member}}
<p>Upgrade to premium for exclusive benefits.</p>
{{/premium_member}}
```

### Nested Conditionals

```handlebars
{{#if order_shipped}}
{{#if tracking_number}}
{{#order_shipped}}
{{#tracking_number}}
<p>Track your order: {{tracking_number}}</p>
{{else}}
{{/tracking_number}}
{{^tracking_number}}
<p>Your order is on its way!</p>
{{/if}}
{{else}}
{{/tracking_number}}
{{/order_shipped}}
{{^order_shipped}}
<p>Your order is being prepared.</p>
{{/if}}
{{/order_shipped}}
```

## Iteration
Expand Down Expand Up @@ -101,9 +118,9 @@ Template:
```handlebars
Hello {{name}},

{{#if premium_member}}
{{#premium_member}}
Thank you for being a premium member!
{{/if}}
{{/premium_member}}

Your order {{order_id}} contains:
{{#each items}}
Expand Down Expand Up @@ -141,6 +158,7 @@ Corresponding `TemplateModel`:
| Mistake | Fix |
|---------|-----|
| `{{html_body}}` renders escaped HTML | Use `{{{html_body}}}` for unescaped HTML |
| Using `{{#if condition}}` | Postmark uses Mustachio — use `{{#property}}` / `{{^property}}` instead |
| `{{#each}}` items without `this.` | Use `{{this.field}}` inside each blocks |
| Missing variable shows as blank | Handlebars renders missing vars as empty string — validate your model |
| Missing variable shows as blank | Mustachio renders missing vars as empty string — validate your model |
| `{{@content}}` in Layout | Must use triple braces: `{{{@content}}}` |