Do not ignore all serde attributes if there are also schemars attributes

schemars_derive/src/preprocess.rs

@@ -1,5 +1,12 @@
-use proc_macro2::Span;
-use syn::{Attribute, Data, DeriveInput, Field, GenericParam, Generics, Ident, Variant};
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use serde_derive_internals::Ctxt;
+use std::collections::BTreeSet;
+use syn::parse::Parser;
+use syn::spanned::Spanned;
+use syn::{
+    Attribute, Data, DeriveInput, Field, GenericParam, Generics, Ident, Meta, NestedMeta, Variant,
+};
 
 pub fn add_trait_bounds(generics: &mut Generics) {
     for param in &mut generics.params {
@@ -11,47 +18,103 @@ pub fn add_trait_bounds(generics: &mut Generics) {
 
 // If a struct/variant/field has any #[schemars] attributes, then rename them
 // to #[serde] so that serde_derive_internals will parse them for us.
-pub fn rename_schemars_attrs(input: &mut DeriveInput) {
-    rename_attrs(input.attrs.iter_mut());
+pub fn process_serde_attrs(input: &mut DeriveInput) -> Result<(), TokenStream> {
+    let ctxt = Ctxt::new();
+    process_attrs(&ctxt, &mut input.attrs);
     match input.data {
-        Data::Struct(ref mut s) => rename_field_attrs(s.fields.iter_mut()),
-        Data::Enum(ref mut e) => rename_variant_attrs(e.variants.iter_mut()),
-        Data::Union(ref mut u) => rename_field_attrs(u.fields.named.iter_mut()),
+        Data::Struct(ref mut s) => process_serde_field_attrs(&ctxt, s.fields.iter_mut()),
+        Data::Enum(ref mut e) => process_serde_variant_attrs(&ctxt, e.variants.iter_mut()),
+        Data::Union(ref mut u) => process_serde_field_attrs(&ctxt, u.fields.named.iter_mut()),
     };
+
+    ctxt.check().map_err(|message| {
+        quote_spanned! {input.span()=>
+            compile_error!(#message);
+        }
+    })
 }
 
-fn rename_variant_attrs<'a>(variants: impl Iterator<Item = &'a mut Variant>) {
+fn process_serde_variant_attrs<'a>(ctxt: &Ctxt, variants: impl Iterator<Item = &'a mut Variant>) {
     for v in variants {
-        rename_attrs(v.attrs.iter_mut());
-        rename_field_attrs(v.fields.iter_mut());
+        process_attrs(&ctxt, &mut v.attrs);
+        process_serde_field_attrs(&ctxt, v.fields.iter_mut());
     }
 }
 
-fn rename_field_attrs<'a>(fields: impl Iterator<Item = &'a mut Field>) {
+fn process_serde_field_attrs<'a>(ctxt: &Ctxt, fields: impl Iterator<Item = &'a mut Field>) {
     for f in fields {
-        rename_attrs(f.attrs.iter_mut());
+        process_attrs(&ctxt, &mut f.attrs);
     }
 }
 
-fn rename_attrs<'a>(attrs: impl Iterator<Item = &'a mut Attribute>) {
-    let (schemars_attrs, others): (Vec<_>, Vec<_>) =
-        attrs.partition(|a| a.path.is_ident("schemars"));
+fn process_attrs(ctxt: &Ctxt, attrs: &mut Vec<Attribute>) {
+    let mut serde_meta: Vec<NestedMeta> = attrs
+        .iter()
+        .filter(|a| a.path.is_ident("serde"))
+        .flat_map(|attr| get_meta_items(&ctxt, attr))
+        .flatten()
+        .collect();
 
-    if !schemars_attrs.is_empty() {
-        for attr in schemars_attrs {
-            let schemars_ident = attr.path.segments.pop().unwrap().into_value().ident;
-            attr.path
-                .segments
-                .push(Ident::new("serde", schemars_ident.span()).into());
+    attrs.retain(|a| a.path.is_ident("schemars"));
+
+    for attr in attrs.iter_mut() {
+        let schemars_ident = attr.path.segments.pop().unwrap().into_value().ident;
+        attr.path
+            .segments
+            .push(Ident::new("serde", schemars_ident.span()).into());
+    }
+
+    let schemars_meta_names: BTreeSet<Ident> = attrs
+        .iter()
+        .flat_map(|attr| get_meta_items(&ctxt, attr))
+        .flatten()
+        .flat_map(|m| get_meta_ident(&ctxt, &m))
+        .collect();
+
+    serde_meta.retain(|m| {
+        get_meta_ident(&ctxt, m)
+            .map(|i| !schemars_meta_names.contains(&i))
+            .unwrap_or(false)
+    });
+
+    if serde_meta.is_empty() {
+        return;
+    }
+
+    let new_serde_attr = quote! {
+        #[serde(#(#serde_meta),*)]
+    };
+
+    let parser = Attribute::parse_outer;
+    match parser.parse2(new_serde_attr) {
+        Ok(ref mut parsed) => attrs.append(parsed),
+        Err(e) => ctxt.error(e),
+    }
+}
+
+fn get_meta_items(ctxt: &Ctxt, attr: &Attribute) -> Result<Vec<NestedMeta>, ()> {
+    match attr.parse_meta() {
+        Ok(Meta::List(meta)) => Ok(meta.nested.into_iter().collect()),
+        Ok(_) => {
+            ctxt.error("expected #[schemars(...)] or #[serde(...)]");
+            Err(())
         }
-        // Give any other attributes a new name so that serde doesn't process them
-        // and complain about duplicate attributes.
-        // TODO we shouldn't need to remove all attributes - it should be possible
-        // to just remove duplicated parts of the attributes.
-        for attr in others {
-            attr.path
-                .segments
-                .push(Ident::new("dummy", Span::call_site()).into());
+        Err(err) => {
+            ctxt.error(err);
+            Err(())
+        }
+    }
+}
+
+fn get_meta_ident(ctxt: &Ctxt, meta: &NestedMeta) -> Result<Ident, ()> {
+    match meta {
+        NestedMeta::Meta(m) => Ok(m.name()),
+        NestedMeta::Literal(lit) => {
+            ctxt.error(format!(
+                "unexpected literal in attribute: {}",
+                lit.into_token_stream()
+            ));
+            Err(())
         }
     }
 }