serde_valid_derive 0.16.0-alpha

JSON Schema based validation tool using with serde.
Documentation 
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use std::collections::HashSet;

use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::parse_quote;
use syn::spanned::Spanned;

use crate::types::CommaSeparatedTokenStreams;

pub fn collect_rules_from_named_struct(
    attributes: &[syn::Attribute],
) -> Result<(HashSet<syn::Ident>, TokenStream), crate::Errors> {
    let mut errors = vec![];

    let mut rule_fields = HashSet::new();
    let rules = attributes
        .iter()
        .filter(|attribute| attribute.path == parse_quote!(rule))
        .filter_map(|attribute| match attribute.parse_meta() {
            Ok(syn::Meta::List(list)) => match collect_rule(&list) {
                Ok((field_ident, stream)) => {
                    rule_fields.extend(field_ident);
                    Some(stream)
                }
                Err(rule_errors) => {
                    errors.extend(rule_errors);
                    None
                }
            },
            Ok(_) => {
                errors.push(crate::Error::rule_need_function(&attribute.path));
                None
            }
            Err(error) => {
                errors.push(crate::Error::rule_validate_attribute_parse_error(
                    attribute, &error,
                ));
                None
            }
        })
        .collect::<Vec<_>>();

    if errors.is_empty() {
        Ok((rule_fields, TokenStream::from_iter(rules)))
    } else {
        Err(errors)
    }
}

fn collect_rule(
    syn::MetaList {
        path, ref nested, ..
    }: &syn::MetaList,
) -> Result<(HashSet<syn::Ident>, TokenStream), crate::Errors> {
    let mut errors = vec![];

    match nested.len() {
        0 => Err(vec![crate::Error::rule_need_function(path)])?,
        2.. => nested.iter().skip(1).for_each(|nested_meta| {
            errors.push(crate::Error::rule_allow_single_function(nested_meta))
        }),
        _ => {}
    }

    let rule = match &nested[0] {
        syn::NestedMeta::Meta(meta) => match meta {
            syn::Meta::List(list) => extract_rule_from_meta_list(list),
            syn::Meta::NameValue(name_value) => {
                Err(vec![crate::Error::meta_name_value_not_support(name_value)])
            }
            syn::Meta::Path(path) => Err(vec![crate::Error::meta_path_not_support(path)]),
        },
        syn::NestedMeta::Lit(lit) => Err(vec![crate::Error::literal_not_support(lit)]),
    };

    match rule {
        Ok(_) => {
            if errors.is_empty() {
                rule
            } else {
                Err(errors)
            }
        }
        Err(rule_errors) => Err(errors.into_iter().chain(rule_errors.into_iter()).collect()),
    }
}

fn extract_rule_from_meta_list(
    syn::MetaList {
        path: rule_fn_name,
        ref nested,
        ..
    }: &syn::MetaList,
) -> Result<(HashSet<syn::Ident>, TokenStream), crate::Errors> {
    let mut errors = vec![];

    if nested.is_empty() {
        errors.push(crate::Error::rule_need_arguments(rule_fn_name));
    }

    let mut arg_idents = HashSet::new();
    let rule_fn_args = nested
        .iter()
        .filter_map(|nested_meta| {
            let arg = match nested_meta {
                syn::NestedMeta::Meta(syn::Meta::Path(path)) => {
                    arg_idents.insert(syn::Ident::new(
                        &path.to_token_stream().to_string(),
                        path.span(),
                    ));
                    Some(quote!(#path))
                }
                _ => None,
            };
            if arg.is_none() {
                errors.push(crate::Error::rule_allow_path_arguments(
                    rule_fn_name,
                    nested_meta,
                ));
            }
            arg
        })
        .collect::<CommaSeparatedTokenStreams>();

    if !errors.is_empty() {
        return Err(errors);
    }

    Ok((
        arg_idents,
        quote!(
            if let Err(__error) = #rule_fn_name(#rule_fn_args) {
                __rule_vec_errors.push(__error);
            };
        ),
    ))
}