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| 1 | +use proc_macro2::{Ident, TokenStream}; |
| 2 | +use quote::{quote, ToTokens}; |
| 3 | +use syn::buffer::Cursor; |
| 4 | +use syn::parse::{Parse, ParseStream}; |
| 5 | +use syn::spanned::Spanned; |
| 6 | +use syn::token::{For, In}; |
| 7 | +use syn::{braced, Expr, Pat}; |
| 8 | + |
| 9 | +use super::{HtmlChildrenTree, ToNodeIterator}; |
| 10 | +use crate::html_tree::HtmlTree; |
| 11 | +use crate::PeekValue; |
| 12 | + |
| 13 | +/// Determines if an expression is guaranteed to always return the same value anywhere. |
| 14 | +fn is_contextless_pure(expr: &Expr) -> bool { |
| 15 | + match expr { |
| 16 | + Expr::Lit(_) => true, |
| 17 | + Expr::Path(path) => path.path.get_ident().is_none(), |
| 18 | + _ => false, |
| 19 | + } |
| 20 | +} |
| 21 | + |
| 22 | +pub struct HtmlFor { |
| 23 | + pat: Pat, |
| 24 | + iter: Expr, |
| 25 | + body: HtmlChildrenTree, |
| 26 | +} |
| 27 | + |
| 28 | +impl PeekValue<()> for HtmlFor { |
| 29 | + fn peek(cursor: Cursor) -> Option<()> { |
| 30 | + let (ident, _) = cursor.ident()?; |
| 31 | + (ident == "for").then_some(()) |
| 32 | + } |
| 33 | +} |
| 34 | + |
| 35 | +impl Parse for HtmlFor { |
| 36 | + fn parse(input: ParseStream) -> syn::Result<Self> { |
| 37 | + For::parse(input)?; |
| 38 | + let pat = Pat::parse_single(input)?; |
| 39 | + In::parse(input)?; |
| 40 | + let iter = Expr::parse_without_eager_brace(input)?; |
| 41 | + |
| 42 | + let body_stream; |
| 43 | + braced!(body_stream in input); |
| 44 | + |
| 45 | + let body = HtmlChildrenTree::parse_delimited(&body_stream)?; |
| 46 | + // TODO: more concise code by using if-let guards once MSRV is raised |
| 47 | + for child in body.0.iter() { |
| 48 | + let HtmlTree::Element(element) = child else { |
| 49 | + continue; |
| 50 | + }; |
| 51 | + |
| 52 | + let Some(key) = &element.props.special.key else { |
| 53 | + continue; |
| 54 | + }; |
| 55 | + |
| 56 | + if is_contextless_pure(&key.value) { |
| 57 | + return Err(syn::Error::new( |
| 58 | + key.value.span(), |
| 59 | + "duplicate key for a node in a `for`-loop\nthis will create elements with \ |
| 60 | + duplicate keys if the loop iterates more than once", |
| 61 | + )); |
| 62 | + } |
| 63 | + } |
| 64 | + Ok(Self { pat, iter, body }) |
| 65 | + } |
| 66 | +} |
| 67 | + |
| 68 | +impl ToTokens for HtmlFor { |
| 69 | + fn to_tokens(&self, tokens: &mut TokenStream) { |
| 70 | + let Self { pat, iter, body } = self; |
| 71 | + let acc = Ident::new("__yew_v", iter.span()); |
| 72 | + |
| 73 | + let alloc_opt = body |
| 74 | + .size_hint() |
| 75 | + .filter(|&size| size > 1) // explicitly reserving space for 1 more element is redundant |
| 76 | + .map(|size| quote!( #acc.reserve(#size) )); |
| 77 | + |
| 78 | + let vlist_gen = match body.fully_keyed() { |
| 79 | + Some(true) => quote! { |
| 80 | + ::yew::virtual_dom::VList::__macro_new( |
| 81 | + #acc, |
| 82 | + ::std::option::Option::None, |
| 83 | + ::yew::virtual_dom::FullyKeyedState::KnownFullyKeyed |
| 84 | + ) |
| 85 | + }, |
| 86 | + Some(false) => quote! { |
| 87 | + ::yew::virtual_dom::VList::__macro_new( |
| 88 | + #acc, |
| 89 | + ::std::option::Option::None, |
| 90 | + ::yew::virtual_dom::FullyKeyedState::KnownMissingKeys |
| 91 | + ) |
| 92 | + }, |
| 93 | + None => quote! { |
| 94 | + ::yew::virtual_dom::VList::with_children(#acc, ::std::option::Option::None) |
| 95 | + }, |
| 96 | + }; |
| 97 | + |
| 98 | + let body = body.0.iter().map(|child| { |
| 99 | + if let Some(child) = child.to_node_iterator_stream() { |
| 100 | + quote!( #acc.extend(#child) ) |
| 101 | + } else { |
| 102 | + quote!( #acc.push(::std::convert::Into::into(#child)) ) |
| 103 | + } |
| 104 | + }); |
| 105 | + |
| 106 | + tokens.extend(quote!({ |
| 107 | + let mut #acc = ::std::vec::Vec::<::yew::virtual_dom::VNode>::new(); |
| 108 | + ::std::iter::Iterator::for_each( |
| 109 | + ::std::iter::IntoIterator::into_iter(#iter), |
| 110 | + |#pat| { #alloc_opt; #(#body);* } |
| 111 | + ); |
| 112 | + #vlist_gen |
| 113 | + })) |
| 114 | + } |
| 115 | +} |
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