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use crate::{convert::FromMeta, DefaultValue};
#[cfg(feature = "legacy")]
use macro_compose::{Collector, Context, Lint};
#[cfg(feature = "legacy")]
use proc_macro2::Span;
use quote::{format_ident, ToTokens};
use std::{iter::FromIterator, mem::replace};
use syn::{
parse::Parse, parse2, parse_quote, punctuated::Punctuated, Attribute, Error, Lit, Meta,
NestedMeta,
};
/// a field definition
/// # Example
/// ```
/// # use macro_input_core as macro_input;
/// use macro_input::{DefaultValue, FieldDef};
///
/// const BAR_FIELD: FieldDef = FieldDef::new("foo", "bar", false, DefaultValue::Bool(None));
/// const BAZ_FIELD: FieldDef = FieldDef::new("foo", "baz", false, DefaultValue::Str(None));
/// ```
pub struct FieldDef<'a> {
/// the path/namespace of the field
pub path: &'a str,
/// the name of the field
pub name: &'a str,
/// whether or not this field is required
pub required: bool,
/// the typed default value
pub default: DefaultValue,
}
impl<'a> FieldDef<'a> {
/// create a new field definition
pub const fn new(path: &'a str, name: &'a str, required: bool, default: DefaultValue) -> Self {
FieldDef {
path,
name,
required,
default,
}
}
/// strip the attributes for this field away
pub fn strip(&self, attrs: &mut Vec<Attribute>) {
let data = replace(attrs, Vec::new());
attrs.extend(data.into_iter().filter_map(|mut a| {
if !self.strip_from_attribute(&mut a) {
Some(a)
} else {
None
}
}));
}
/// strip the attribute and return if it is empty
fn strip_from_attribute(&self, attr: &mut Attribute) -> bool {
let mut meta = attr.parse_meta().unwrap();
// check the path
if !meta.path().is_ident(self.path) {
return false;
}
match &mut meta {
Meta::List(list) => {
let new_punctuated = list
.nested
.iter()
.filter(|meta| {
if let NestedMeta::Meta(meta) = meta {
!meta.path().is_ident(self.name)
} else {
true
}
})
.cloned();
list.nested = Punctuated::from_iter(new_punctuated);
let empty = list.nested.is_empty();
attr.tokens = parse_quote!(#meta);
empty
}
Meta::Path(_) => true,
_ => false,
}
}
/// try to find the meta that has the value for this field
pub fn get_meta(&self, attrs: &[Attribute]) -> Option<Meta> {
for attr in attrs.iter() {
let meta = attr.parse_meta().unwrap();
if meta.path().is_ident(self.path) {
if let Meta::List(list) = meta {
for meta in list.nested.iter() {
if let NestedMeta::Meta(meta) = meta {
if meta.path().is_ident(self.name) {
return Some(meta.clone());
}
}
}
}
}
}
if self.required {
panic!(
"attribute for required field not found: {}::{}",
self.path, self.name
);
}
// construct a default meta
if let Some(lit) = self.default.as_lit() {
let name = format_ident!("{}", self.path);
return Some(parse_quote!(#name = #lit));
}
None
}
/// try to find the literal that has the value for this field
pub fn get_lit(&self, attrs: &[Attribute]) -> Option<Lit> {
self.get_meta(attrs).and_then(|m| match m {
Meta::NameValue(nvm) => Some(nvm.lit),
_ => None,
})
}
/// try to parse the literal that has the value for this field
pub fn get<L: Parse>(&self, attrs: &[Attribute]) -> Option<L> {
self.get_lit(attrs).map(|lit| {
let tokens = lit.to_token_stream();
parse2(tokens).unwrap()
})
}
/// try to extract the value from the literal that has the value for this field
pub fn get_value<V: FromMeta>(&self, attrs: &[Attribute]) -> Result<V, Error> {
FromMeta::from(self.get_meta(attrs))
}
}
#[cfg(feature = "legacy")]
impl Lint<Vec<Attribute>> for FieldDef<'_> {
fn lint(&self, input: &Vec<Attribute>, c: &mut Collector) {
let mut found = false;
for attr in input.iter() {
let meta = attr.parse_meta().unwrap();
if meta.path().is_ident(self.path) {
if let Meta::List(list) = meta {
for meta in list.nested.iter() {
if let NestedMeta::Meta(meta) = meta {
if meta.path().is_ident(self.name) {
match meta {
Meta::NameValue(meta) => {
if found {
c.error(Error::new_spanned(
meta,
format!("dupplicate {} attribute", self.path),
));
} else {
found = true;
}
let some_lit = Some(&meta.lit);
let mut subcontext = Context::new_by_ref(c, &some_lit);
subcontext.lint(
&self
.default
.ty(!self.required
&& !self.default.has_default_data()),
);
}
Meta::Path(_) => {
if found {
c.error(Error::new_spanned(
meta,
format!("dupplicate {} attribute", self.path),
));
} else {
found = true;
}
let mut subcontext = Context::new_by_ref(c, &None);
subcontext.lint(
&self
.default
.ty(!self.required
&& !self.default.has_default_data()),
);
}
_ => {
c.error(Error::new_spanned(&meta, "unexpected meta list"));
}
}
}
}
}
}
}
}
if !found && self.required {
c.error(Error::new(
Span::call_site(),
format!("missing required {} attribute", self.name),
));
}
}
}