Force a specific mode using {# fmt:mode #}

[JaapJoris]

Closes #110

[JaapJoris]

This was removed because it's hardly "new" anymore. I replaced it with a representative example of DjHTML's output at the top of this file.

[ErwinJunge]

I don't understand, when would the fmt:css end in this example? Doesn't this need some sort of endfmt:css? Or perhaps fmt:auto to go back to whatever fmt:on does?

[JaapJoris]

when would the fmt:css end in this example?

Until one of the following strings is encountered:

• {# fmt:html #}
• {# fmt:js #}
• </style>

You should know that the tokenizer of DjHTML is pretty dumb. It processes the input file line by line, token by token, and switches to different modes when it encounters certain tokens. For example, when the token <script> is encountered in DjHTML mode, it switches to DjJS mode. Each mode is an instance of its class, and the previous mode instance is stored as self.return_mode. Each mode normally only looks at the contents of the token it's currently processing, although there are some look-ahead assertions in a few places. It never looks back.

Therefore, a reasonable implementation of a potential {# fmt:auto #} would be to return to the mode it came from, which is technically not "auto-detecting" the appropriate mode at all, but simply deterministically unstacking the order of modes. {# fmt:previous #} would be more correct.

However, if you want to switch to a different mode you could also just specify the mode explicitly, which is better than implicitly. Here's how I would imagine the the original bug reporter using these new tags:

{% block style %}
    {# fmt:css %}
    {{ block.super }}
    .somemorecss {
        somemoreproperty: somemorevalue;
    }
{% endblock %}

{% block content %}
    {# fmt:html #}
    <main>
        <article>...</article>
    </main>
{% endblock %}

That the indenter remains in DjCSS mode until it encounters a different {# fmt #} tag is kinda weird, though. For example, if you switch the above two blocks around, indentation will fail as it will remain in DjCSS mode indefinitely. It may also lead to other problems that I have not foreseen.

I'm open to other suggestions on how to implement mode switches, and even to other suggestions on how to solve OP's problem 🙏

[ErwinJunge]

How about reverting to the previous formatter on endblock if a format was explicitly requested for a block? So you can think of the fmt:css as an "attribute" of the django block.

[JaapJoris]

For this specific use case, that would work. However, there are plenty more use cases for overriding modes, for example:

<a onclick="
    {# fmt:js #}
    var links = document.querySelectorAll('a');
    for (var i = 0; i < links.length; i++) {
        links[i].click();
    }
    ">
    {# fmt:html #}
    Click me!
</a>

[ErwinJunge]

Then you really need something that ends it explicitly I think. endfmt:html perhaps? As a bonus, you could then perhaps try checking that each explicit fmt:xxx call has a matching endfmt:xxx call, although that would likely make keeping track of the callstack complex 🤔

[JaapJoris]

The above example does illustrate the need for a {# fmt:auto #}, though, because when inside a HTML element using {# fmt:html #} will have unpredictable results at best. I'll see what I can do.

[JaapJoris]

I cannot solve this:

<div>
    <blockquote cite="#103"
                x-data="
                        {# fmt:js #}
                        function() {
                            foo();
                        }
                        {# fmt:auto #}
                       "
                class="foo"
    />
    <blockquote
        cite="#110"
        style="{# fmt:css #}
               font-family: Arial,
                            Helvetica;
               {# fmt:auto #}"
    />
</div>

This makes me arrive at the same conclusion that I arrived at earlier in #103:

The {# fmt:<mode> #} option seems like a good idea though, so I experimented a bit with it. The problem is that it's hard to "exit" this mode again without running into inconsistencies.

So, I have decided to decline this PR.

[JaapJoris]

Impossible.