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|
use std::collections::VecDeque;
use proc_macro2::{Ident, TokenStream};
use quote::quote;
use syn::{
punctuated::Punctuated, spanned::Spanned, token::Comma, Error, FnArg, Generics, Pat, PatType,
Path, Result, ReturnType, Signature, Type,
};
pub struct Components {
pub name: Ident,
pub generics: Generics,
pub validator_name: Ident,
pub evaluator_name: Ident,
pub result: TokenStream,
pub ret: ReturnType,
pub inputs: Punctuated<FnArg, Comma>,
pub args: VecDeque<FnArgument>,
}
pub struct FnArgument {
pub ident: Ident,
pub ty: TokenStream,
}
fn extract_pat_ident(pat: &Pat) -> Option<Ident> {
if let Pat::Ident(ref pat_ident) = pat {
Some(pat_ident.ident.to_owned())
} else {
None
}
}
fn extract_type_path(ty: &Type) -> Option<&Path> {
match ty {
Type::Path(ref typepath) if typepath.qself.is_none() => Some(&typepath.path),
Type::Reference(ref typeref) => match *typeref.elem {
Type::Path(ref typepath) if typepath.qself.is_none() => Some(&typepath.path),
_ => None,
},
_ => None,
}
}
fn extract_json_path_type(p: &Path) -> Result<TokenStream> {
let p_seg = p
.segments
.last()
.ok_or_else(|| Error::new(p.span(), "expected a type identifier"))?;
let ts = match p_seg.ident.to_string().as_str() {
"NodesType" => quote! {
::serde_json_path_macros::serde_json_path_core::spec::functions::NodesType
},
"ValueType" => quote! {
::serde_json_path_macros::serde_json_path_core::spec::functions::ValueType
},
"LogicalType" => quote! {
::serde_json_path_macros::serde_json_path_core::spec::functions::LogicalType
},
other => {
return Err(Error::new(
p_seg.ident.span(),
format!(
"expected 'NodesType', 'ValueType', or 'LogicalType', got '{}'",
other,
),
))
}
};
Ok(ts)
}
pub fn extract_components(input: Signature) -> Result<Components> {
let name = input.ident.clone();
let generics = input.generics.clone();
let inputs = input.inputs.clone();
let ret = input.output.clone();
let result = match &ret {
ReturnType::Default => {
return Err(Error::new(
input.span(),
"function signature expected to have return type",
))
}
ReturnType::Type(_, ty) => {
if let Some(path) = extract_type_path(ty.as_ref()) {
extract_json_path_type(path)?
} else {
return Err(Error::new(
ty.span(),
"return type can only be one of the serde_json_path types: NodesType, \
ValueType, or LogicalType",
));
}
}
};
let args: Result<VecDeque<FnArgument>> = inputs
.iter()
.map(|i| match i {
FnArg::Receiver(_) => Err(Error::new(
inputs.span(),
"receiver arguments like self, &self, or &mut self are not supported",
)),
FnArg::Typed(PatType {
attrs: _,
pat,
colon_token: _,
ty,
}) => {
let ident = if let Some(id) = extract_pat_ident(pat) {
id
} else {
return Err(Error::new(
pat.span(),
"expected identifier in function argument",
));
};
let ty = if let Some(path) = extract_type_path(ty) {
extract_json_path_type(path)?
} else {
return Err(Error::new(
ty.span(),
"argument type can only be one of the serde_json_path types: NodesType, \
ValueType, or LogicalType",
));
};
Ok(FnArgument { ident, ty })
}
})
.collect();
let args = args?;
let validator_name = Ident::new(
format!("{name}_validator").to_uppercase().as_str(),
name.span(),
);
let evaluator_name = Ident::new(
format!("{name}_evaluator").to_uppercase().as_str(),
name.span(),
);
Ok(Components {
name,
generics,
result,
inputs,
ret,
args,
validator_name,
evaluator_name,
})
}
|
