Template of Structure Containing Enum

[kulak]

I tried to apply a template to structure that contained enum and it did not work:

struct ParsedContent {
  tokens: Vec<Token>
}

where Token is the enum.

I wounder if there is something I did not do to get it working, because example in the documentation is Enums with directly attached templates.

The only solution I currently see is the creation of the same data type and copy of data between the original and the target enum.

[GuillaumeGomez]

"it did not work". Great, I love divination. :)

Some useful information:

• Version of askama
• Output of the error

[kulak]

I reproduced the problem to make it clear.

#[derive(Debug, Template)]
#[template(path = "part-content.html")]
pub struct ContentTemplate {
    pub tokens: Vec<Token>
}

#[derive(Debug, PartialEq)]
pub enum Token {
    NostrBech32(String, String), // HMR, Bech32
    Paragraph(String),
    Link(String, String), // url, domain
}

Jinja template file:

{% for token in tokens %}
    {%- match token -%}
        {%- when Self::Paragraph(text) -%}
            <p class='p-1'>{{text}}</p>
        {%- when Self::NostrBech32(hmr, encoded) -%}
            <p class='p-1 text-orange-500'>nostr:{{hmr}}</p>
        {%- when Self::Link(link, domain) -%}
            <p class='p-1 text-blue-500'>Jump: <a href='{{link}}'>{{domain}}</a></p>
    {%- endmatch -%}
{% endfor %}

Here is cargo build output:

error[E0599]: no associated item named `Paragraph` found for struct `ContentTemplate` in the current scope
 --> website/src/nip1tokenizer.rs:6:17
  |
6 | #[derive(Debug, Template)]
  |                 ^^^^^^^^ associated item not found in `ContentTemplate`
7 | #[template(path = "part-content.html")]
8 | pub struct ContentTemplate {
  | -------------------------- associated item `Paragraph` not found for this struct
  |
  = note: this error originates in the derive macro `Template` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no associated item named `NostrBech32` found for struct `ContentTemplate` in the current scope
 --> website/src/nip1tokenizer.rs:6:17
  |
6 | #[derive(Debug, Template)]
  |                 ^^^^^^^^ associated item not found in `ContentTemplate`
7 | #[template(path = "part-content.html")]
8 | pub struct ContentTemplate {
  | -------------------------- associated item `NostrBech32` not found for this struct
  |
  = note: this error originates in the derive macro `Template` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no associated item named `Link` found for struct `ContentTemplate` in the current scope
 --> website/src/nip1tokenizer.rs:6:17
  |
6 | #[derive(Debug, Template)]
  |                 ^^^^^^^^ associated item not found in `ContentTemplate`
7 | #[template(path = "part-content.html")]
8 | pub struct ContentTemplate {
  | -------------------------- associated item `Link` not found for this struct
  |
  = note: this error originates in the derive macro `Template` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0599`.
warning: `website` (lib) generated 2 warnings
error: could not compile `website` (lib) due to 3 previous errors; 2 warnings emitted

[GuillaumeGomez]

Let me translate your jinja template in rust so we can see better what's going on:

impl AskamaRender for ContentTemplate {
    fn render(&self) {
        for token in &self.tokens {
            match token {
                Self::Paragraph(text) => println!("<p class='p-1'>{text}</p>"),
                Self::NostrBech32(hmr, encoded) => println!("<p class='p-1 text-orange-500'>nostr:{hmr}</p>"),
                Self::Link(link, domain) => println!("<p class='p-1 text-blue-500'>Jump: <a href='{link}'>{domain}</a></p>"),
            }
        }
    }
}

So, unless I missed something, Self in here refers to ContentTemplate. And ContentTemplate doesn't contain the variant you're matching on. So instead of Self, you're supposed to use Token.

[Kijewski]

Templates can be used with borrowed data, too:

#[derive(Template)]
#[template(path = "parsed_content.html")]
struct ParsedContent<'a> {
    tokens: &'a [Token]
}

Then you can make the Token a Template, too:

#[derive(Template)]
enum Token {
    #[template(...)]
    A,
    #[template(...)]
    B,
    #[template(...)]
    C,
}

parsed_content.html:

<ol>
{% for token in tokens %}
    <li>{{ token | safe }}</li>
{% endfor %}
</ol>