Support else ifs in conditional attributes

[dimmerz92]

Describe the bug
Writing a template that contains a simple if, else if, else.

The bug I am experiencing is that the else if is not respected. the else in the else if ends up becoming an attribute in the HTML component and the if statement starts again on the second if with the final else being respected.

Note: I have noticed that the LSP will reformat it, however, I have saved with :noa w to prevent formatting and I still get this issue. So I don't believe this is an LSP issue.

To Reproduce

var DefaultStyle = "some-default-class"

type ButtonProps struct {
    Classes     string
    ButtonStyle string
    VoidStyle   bool
}

templ Button(props ButtonProps) {
    <button
        if props.VoidStyle {
            class={ props.Classes }
        } else if props.ButtonStyle != "" {
            class={ props.ButtonStyle, props.Classes }
        } else {
            class={ DefaultStyle, props.Classes }
        }
    >
        { Test Button }
    </button>
}

Expected behavior
I would expect that the if, else if, and else are all evaluated as necessary.

Screenshots
In use:

The relevant part of the component:

After the LSP has its way with it:

Rendered in the browser:

Logs
If the issue is related to IDE support, run through the LSP troubleshooting section at https://templ.guide/commands-and-tools/ide-support/#troubleshooting-1 and include logs from templ

templ info output
Run templ info and include the output.

Desktop (please complete the following information):

(✓) os [ goos=linux goarch=amd64 ]
(✓) go [ location=/usr/local/go/bin/go version=go version go1.22.5 linux/amd64 ]
(✓) gopls [ location=/home/andrew/go/bin/gopls version=golang.org/x/tools/gopls v0.16.2 ]
(✓) templ [ location=/home/andrew/go/bin/templ version=v0.2.778 ]

[dimmerz92]

There is a more comprehensive example that I just merged into my dev branch here: https://github.com/dimmerz92/htemplx

From a few tests, it looks like it still evaluates correctly?, but it still leaves a vestigial else="" in the html tag.

[joerdav]

I'll take a look at this, I imagine there is a bug in the parser code causing this.

[joerdav]

After some more digging I realised this is not a bug, but an unimplemented feature. Currently attributes do not support "else if" only simple if and else clauses.

[dimmerz92]

No worries!

Out of curiosity, because it still seems to work as expected, is this just a case of the second following if and else statements potentially still getting evaluated in some cases, but not assigning class a second time?