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Document template inheritance block naming restrictions #1090

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malteneuss opened this issue Aug 30, 2024 · 2 comments
Open

Document template inheritance block naming restrictions #1090

malteneuss opened this issue Aug 30, 2024 · 2 comments

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@malteneuss
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malteneuss commented Aug 30, 2024 •
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I just stumbled upon an unexpected quirk where apparently hyphens are not allowed in template block names:

<html lang="en">
  <head>
    {% block a-head %}{% endblock %}
  </head>
</html>

results in a vague error like

error: problems parsing template source at row 7, column 15 near:
       "head %}\n..."
  --> website/src/routes.rs:12:10
   |
12 | #[derive(Template)]

while {% block head %} works as expected. I would like to document the naming restrictions if someone knows them or could point me to source code that parses such expressions.
@djc
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djc commented Sep 2, 2024

Thanks for the report. The parser lives here:

https://github.com/djc/askama/blob/main/askama_parser/src/node.rs#L778

Some documentation would be great -- we could also consider relaxing the grammar it accepts, assuming that doesn't add too much complexity.

@malteneuss
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malteneuss commented Sep 7, 2024 •
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Thanks for the hint. Skimming through the code i found out that "identifier" is the function that restricts the names to alphabetic characters only (by delegating to https://docs.rs/nom/latest/src/nom/traits.rs.html#246). As identifier is used quite often in https://docs.rs/nom/latest/src/nom/traits.rs.html#246 for many Node types, i wouldn't add a naming hint for blocks only; and i wouldn't want to duplicate the same hint for almost all Node types in the book.
=> The best solution would be to allow the same names as Rust allows (as for top-level variables) if possible. Unfortunately, i don't consider myself knowledgeable enough to implement that. Feel free to close this issue, if there's other more urgent work.

@djc djc changed the title Document template inheritence block naming restrictions Document template inheritance block naming restrictions Sep 9, 2024
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@djc @malteneuss