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use {
crate::{grammar, ParseResult},
quote::quote,
syn::{
braced,
parse::{Parse, ParseStream},
punctuated::Punctuated,
Attribute, Ident, Item, Token, Visibility,
},
};
pub(crate) struct PragmaInput {
pub(crate) items: Punctuated<PragmaItem, Token![;]>,
}
impl Parse for PragmaInput {
fn parse(input: ParseStream) -> ParseResult<Self> {
let mut items = Punctuated::new();
while !input.is_empty() {
let itm = input.parse::<PragmaItem>()?;
items.push(itm);
if input.peek(Token![;]) {
input.parse::<Token![;]>()?;
}
}
Ok(PragmaInput { items })
}
}
pub(crate) enum PragmaItemContent {
Normal(Item),
Mod { ident: Ident, content: PragmaInput },
}
pub(crate) struct PragmaItem {
pub(crate) attrs: Vec<Attribute>,
pub(crate) visibility: Visibility,
pub(crate) condition: Option<grammar::ConditionExpr>,
pub(crate) content: PragmaItemContent,
}
impl Parse for PragmaItem {
fn parse(input: ParseStream) -> ParseResult<Self> {
// parse attributes
let attrs = input.call(syn::Attribute::parse_outer)?;
// parse visibility
let visibility: Visibility = input.parse()?;
// check if we have `(if ...)`
let condition = if input.peek(syn::token::Paren) {
let content;
let _paren = syn::parenthesized!(content in input);
content.parse::<Token![if]>()?;
let cond_expr = grammar::parse_condition(&&content)?;
Some(cond_expr)
} else {
None
};
if input.peek(Token![mod]) {
// parse a module
input.parse::<Token![mod]>()?;
let ident: Ident = input.parse()?;
let content_stream;
let _brace = braced!(content_stream in input);
let mut items = Punctuated::new();
while !content_stream.is_empty() {
let itm = content_stream.parse::<PragmaItem>()?;
items.push(itm);
if content_stream.peek(Token![;]) {
content_stream.parse::<Token![;]>()?;
}
}
let inner_input = PragmaInput { items };
Ok(PragmaItem {
attrs,
visibility,
condition,
content: PragmaItemContent::Mod {
ident,
content: inner_input,
},
})
} else {
// normal item
let item: Item = input.parse()?;
Ok(PragmaItem {
attrs,
visibility,
condition,
content: PragmaItemContent::Normal(item),
})
}
}
}
pub(crate) fn process_pragma_input(input: PragmaInput) -> proc_macro2::TokenStream {
let tokens = input.items.into_iter().map(|item| {
let PragmaItem {
attrs,
visibility,
condition,
content,
} = item;
match content {
PragmaItemContent::Normal(item) => {
if let Some(cond) = condition {
let main_condition = grammar::condition_to_cfg(&cond);
let inverse_condition = quote! { not(#main_condition) };
match &visibility {
Visibility::Inherited => {
// single version for (if condition) no visibility
quote! {
#[cfg(#main_condition)]
#(#attrs)*
#item
}
}
_ => {
// two versions for pub (if condition)
let public_item = quote! {
#[cfg(#main_condition)]
#(#attrs)*
#visibility #item
};
let private_item = quote! {
#[cfg(#inverse_condition)]
#(#attrs)*
#item
};
quote! {
#public_item
#private_item
}
}
}
} else {
// unconditional item
quote! {
#(#attrs)*
#visibility #item
}
}
}
PragmaItemContent::Mod {
ident,
content: inner_input,
} => {
let inner_tokens = process_pragma_input(inner_input);
if let Some(cond) = condition {
let main_condition = grammar::condition_to_cfg(&cond);
let inverse_condition = quote! { not(#main_condition) };
match &visibility {
Visibility::Inherited => {
quote! {
#[cfg(#main_condition)]
#(#attrs)*
mod #ident {
#inner_tokens
}
}
}
_ => {
let public_item = quote! {
#[cfg(#main_condition)]
#(#attrs)*
#visibility mod #ident {
#inner_tokens
}
};
let private_item = quote! {
#[cfg(#inverse_condition)]
#(#attrs)*
mod #ident {
#inner_tokens
}
};
quote! {
#public_item
#private_item
}
}
}
} else {
// unconditional mod
quote! {
#(#attrs)*
#visibility mod #ident {
#inner_tokens
}
}
}
}
}
});
quote! {
#(#tokens)*
}
}