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Can't pass single-quoted strings as parameters #575

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nickvollmar opened this issue May 2, 2023 · 1 comment
Closed

Can't pass single-quoted strings as parameters #575

nickvollmar opened this issue May 2, 2023 · 1 comment
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enhancement syntax

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@nickvollmar
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Reproduction

In tests/helper_macro.rs, within the function test_macro_helper, you can add the following assertion.

    assert_eq!(
        hbs.render_template("{{tag 'html'}}", &()).unwrap(),
        "<html>"
    );
thread 'test_macro_helper' panicked at 'called `Result::unwrap()` on an `Err` value: RenderError { desc: "`tag` helper: Couldn't convert parameter t to type `str`. It's Null as JSON. Got these params: [PathAndJson { relative_path: Some(\"'html'\"), value: Missing }]", template_name: None, line_no: Some(1), column_no: Some(1), cause: None, unimplemented: false }', tests/helper_macro.rs:77:52

Cause

I believe the origin of this behavior is

handlebars-rust/src/template.rs

Lines 292 to 296 in 27a9a9a

if let Ok(json) = Json::from_str(s) {
Parameter::Literal(json)
} else {
Parameter::Name(s.to_owned())
}

The single-quoted literal matches the Rule::literal parser rule, but it is not valid JSON, so it becomes a Name object.

As evidence of this, here is the data structure I get by parsing the template {{tag 'html'}}:

Template {
  name: None,
  elements: [
    Expression(HelperTemplate {
      name: Name("tag"),
      params: [Name("'html'")],
      hash: {},
      block_param: None,
      template: None,
      inverse: None,
      block: false
    })
  ],
  mapping: [TemplateMapping(1, 1)]
}

Proposal

I think the way forward is to somehow extract more information from the pest parse results.

Here is a rough sketch of how I think that logic might look. As you can see, I'm out of my depth here, but this passes all the tests!

Rule::literal => {
    let param = param.into_inner().next().unwrap();
    match param.as_rule() {
        Rule::string_literal => {
            let string_inner = param.into_inner().next().unwrap();
            // don't double-escape characters - see test_string_no_escape_422
            let double_quoted = format!("\"{}\"", string_inner.as_str());
            Parameter::Literal(Json::from_str(&double_quoted).unwrap())
        }
        _ => {
            Parameter::Literal(Json::from_str(param_span.as_str()).unwrap())
        }
    }
}

(In the suggestion above I removed the Name code path, since I don't think any other JSON data type would make sense as a Name.)

Thank you very much, for reading this report and for all your work on this project.
@sunng87
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sunng87 commented May 4, 2023

Thank you for reporting and the solution looks good to me. Could you please create a pull request for this?

@nickvollmar nickvollmar mentioned this issue May 5, 2023
Merged
@sunng87 sunng87 closed this as completed May 13, 2023
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@sunng87 @nickvollmar