# `Mailglass.TemplateEngine.HEEx`
[🔗](https://github.com/szTheory/mailglass/blob/v1.0.0/lib/mailglass/template_engine/heex.ex#L1)

Default HEEx template engine for mailglass.

Renders a pre-compiled Phoenix function component by calling it with the
provided assigns and converting the result to iodata via `Phoenix.HTML.Safe`.

## Usage

HEEx templates are compiled by the Phoenix tag engine at build time. Callers
pass the already-compiled function component (a `fn assigns -> ... end` or
`&MyModule.component/1`) directly to `render/3`. The `compile/2` callback
returns `{:ok, :heex_native}` for API symmetry.

## Error Handling

- Missing assign (`KeyError`) → `{:error, %Mailglass.TemplateError{type: :missing_assign}}`
- Argument errors during render → `{:error, %Mailglass.TemplateError{type: :missing_assign}}`
- Any other runtime error → `{:error, %Mailglass.TemplateError{type: :heex_compile}}`
- Non-function `compiled` argument → `{:error, %Mailglass.TemplateError{type: :heex_compile}}`

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*Consult [api-reference.md](api-reference.md) for complete listing*