Interaction between IfmtInput::push_* and rsx-autoformat

[ealmloff]

Problem

IfmtInput has methods like push_raw_str to modify the segments, but those methods do not effect the source. Since the autoformatter only uses the source it was originally parsed from formatting a ifmt segment reverts the segments that were pushed. This behavior caused this bug in the docsite codegen. The patch works around the issue by not merging adjacent text segments

Steps To Reproduce

Run this code and observe it panics:

#[test]
fn fails() {
    let mut rsx: CallBody = parse_quote! { "hello world" };
    if let dioxus_rsx::BodyNode::Text(text) = &mut rsx.body.roots[0] {
        // Modifying the IfmtInput directly is allowed, but it doesn't update the source that autofmt uses
        text.input
            .formatted_input
            .push_raw_str(" this isn't added to the formatted version".to_string());
    }
    let block = dioxus_autofmt::write_block_out(&rsx).unwrap();
    let re_parsed: CallBody = syn::parse_str(&block).unwrap();

    // normalize line endings for windows tests to pass
    assert_eq!(rsx.body, re_parsed.body);
}

Expected behavior

You should not be able to edit IfmtInput internals or modifying IfmtInput should work with the autoformatter

Environment:

• Dioxus version: master
• Rust version: nightly
• OS info: MacOS

[jkelleyrtp]

I think we might be able to get around the need for spans by simply not caching expressions at all. I think we used spans at one point but recent improvements mean we use span information just for caching the expression which we really don't need to do.