Release 1.0.183

Refactor code that generates `__Field` enums

precompiled/bin/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.181"
+version = "1.0.183"
 authors = ["David Tolnay <dtolnay@gmail.com>"]
 publish = false
 

precompiled/serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.181"
+version = "1.0.183"
 authors = ["David Tolnay <dtolnay@gmail.com>"]
 categories = ["no-std", "no-std::no-alloc"]
 description = "Implementation of #[derive(Serialize, Deserialize)]"

precompiled/serde_derive/src/lib.rs

@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.181")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.183")]
 
 #[cfg(not(all(target_arch = "x86_64", target_os = "linux", target_env = "gnu")))]
 include!("lib_from_source.rs");

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.181" # remember to update html_root_url and serde_derive dependency
+version = "1.0.183" # remember to update html_root_url and serde_derive dependency
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 build = "build.rs"
 categories = ["encoding", "no-std", "no-std::no-alloc"]
@@ -15,7 +15,7 @@ repository = "https://github.com/serde-rs/serde"
 rust-version = "1.31"
 
 [dependencies]
-serde_derive = { version = "=1.0.181", optional = true, path = "../serde_derive" }
+serde_derive = { version = "=1.0.183", optional = true, path = "../serde_derive" }
 
 [dev-dependencies]
 serde_derive = { version = "1", path = "../serde_derive" }

serde/src/de/impls.rs

@@ -1789,6 +1789,9 @@ forwarded_impl!((T), Box<[T]>, Vec::into_boxed_slice);
 #[cfg(any(feature = "std", feature = "alloc"))]
 forwarded_impl!((), Box<str>, String::into_boxed_str);
 
+#[cfg(all(feature = "std", any(unix, windows)))]
+forwarded_impl!((), Box<OsStr>, OsString::into_boxed_os_str);
+
 #[cfg(any(feature = "std", feature = "alloc"))]
 impl<'de, 'a, T: ?Sized> Deserialize<'de> for Cow<'a, T>
 where

serde/src/lib.rs

@@ -93,7 +93,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.181")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.183")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Unstable functionality only if the user asks for it. For tracking and

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.181" # remember to update html_root_url
+version = "1.0.183" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 categories = ["no-std", "no-std::no-alloc"]
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"

serde_derive/src/de.rs

@@ -723,19 +723,11 @@ fn deserialize_seq(
                     })
                 }
             };
-            let value_if_none = match field.attrs.default() {
+            let value_if_none = expr_is_missing_seq(None, index_in_seq, field, cattrs, expecting);
-                attr::Default::Default => quote!(_serde::__private::Default::default()),
-                attr::Default::Path(path) => quote!(#path()),
-                attr::Default::None => quote!(
-                    return _serde::__private::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
-                ),
-            };
             let assign = quote! {
                 let #var = match #visit {
                     _serde::__private::Some(__value) => __value,
-                    _serde::__private::None => {
+                    _serde::__private::None => #value_if_none,
-                        #value_if_none
-                    }
                 };
             };
             index_in_seq += 1;
@@ -811,24 +803,14 @@ fn deserialize_seq_in_place(
                 self.place.#member = #default;
             }
         } else {
-            let value_if_none = match field.attrs.default() {
+            let value_if_none = expr_is_missing_seq(Some(quote!(self.place.#member = )), index_in_seq, field, cattrs, expecting);
-                attr::Default::Default => quote!(
-                    self.place.#member = _serde::__private::Default::default();
-                ),
-                attr::Default::Path(path) => quote!(
-                    self.place.#member = #path();
-                ),
-                attr::Default::None => quote!(
-                    return _serde::__private::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
-                ),
-            };
             let write = match field.attrs.deserialize_with() {
                 None => {
                     quote! {
                         if let _serde::__private::None = _serde::de::SeqAccess::next_element_seed(&mut __seq,
                             _serde::__private::de::InPlaceSeed(&mut self.place.#member))?
                         {
-                            #value_if_none
+                            #value_if_none;
                         }
                     }
                 }
@@ -841,7 +823,7 @@ fn deserialize_seq_in_place(
                                 self.place.#member = __wrap.value;
                             }
                             _serde::__private::None => {
-                                #value_if_none
+                                #value_if_none;
                             }
                         }
                     })
@@ -983,12 +965,7 @@ fn deserialize_struct(
             )
         })
         .collect();
-    let field_visitor = Stmts(deserialize_generated_identifier(
+    let field_visitor = deserialize_field_identifier(&field_names_idents, cattrs);
-        &field_names_idents,
-        cattrs,
-        false,
-        None,
-    ));
 
     // untagged struct variants do not get a visit_seq method. The same applies to
     // structs that only have a map representation.
@@ -1040,7 +1017,7 @@ fn deserialize_struct(
     } else {
         let field_names = field_names_idents
             .iter()
-            .flat_map(|(_, _, aliases)| aliases);
+            .flat_map(|&(_, _, aliases)| aliases);
 
         Some(quote! {
             #[doc(hidden)]
@@ -1146,12 +1123,7 @@ fn deserialize_struct_in_place(
         })
         .collect();
 
-    let field_visitor = Stmts(deserialize_generated_identifier(
+    let field_visitor = deserialize_field_identifier(&field_names_idents, cattrs);
-        &field_names_idents,
-        cattrs,
-        false,
-        None,
-    ));
 
     let mut_seq = if field_names_idents.is_empty() {
         quote!(_)
@@ -1162,7 +1134,7 @@ fn deserialize_struct_in_place(
     let visit_map = Stmts(deserialize_map_in_place(params, fields, cattrs));
     let field_names = field_names_idents
         .iter()
-        .flat_map(|(_, _, aliases)| aliases);
+        .flat_map(|&(_, _, aliases)| aliases);
     let type_name = cattrs.name().deserialize_name();
 
     let in_place_impl_generics = de_impl_generics.in_place();
@@ -1265,7 +1237,12 @@ fn prepare_enum_variant_enum(
         })
         .collect();
 
-    let other_idx = deserialized_variants.position(|(_, variant)| variant.attrs.other());
+    let fallthrough = deserialized_variants
+        .position(|(_, variant)| variant.attrs.other())
+        .map(|other_idx| {
+            let ignore_variant = variant_names_idents[other_idx].1.clone();
+            quote!(_serde::__private::Ok(__Field::#ignore_variant))
+        });
 
     let variants_stmt = {
         let variant_names = variant_names_idents.iter().map(|(name, _, _)| name);
@@ -1279,7 +1256,8 @@ fn prepare_enum_variant_enum(
         &variant_names_idents,
         cattrs,
         true,
-        other_idx,
+        None,
+        fallthrough,
     ));
 
     (variants_stmt, variant_visitor)
@@ -2001,30 +1979,15 @@ fn deserialize_untagged_newtype_variant(
 }
 
 fn deserialize_generated_identifier(
-    fields: &[(String, Ident, Vec<String>)],
+    fields: &[(&str, Ident, &BTreeSet<String>)],
     cattrs: &attr::Container,
     is_variant: bool,
-    other_idx: Option<usize>,
+    ignore_variant: Option<TokenStream>,
+    fallthrough: Option<TokenStream>,
 ) -> Fragment {
     let this_value = quote!(__Field);
     let field_idents: &Vec<_> = &fields.iter().map(|(_, ident, _)| ident).collect();
 
-    let (ignore_variant, fallthrough) = if !is_variant && cattrs.has_flatten() {
-        let ignore_variant = quote!(__other(_serde::__private::de::Content<'de>),);
-        let fallthrough = quote!(_serde::__private::Ok(__Field::__other(__value)));
-        (Some(ignore_variant), Some(fallthrough))
-    } else if let Some(other_idx) = other_idx {
-        let ignore_variant = fields[other_idx].1.clone();
-        let fallthrough = quote!(_serde::__private::Ok(__Field::#ignore_variant));
-        (None, Some(fallthrough))
-    } else if is_variant || cattrs.deny_unknown_fields() {
-        (None, None)
-    } else {
-        let ignore_variant = quote!(__ignore,);
-        let fallthrough = quote!(_serde::__private::Ok(__Field::__ignore));
-        (Some(ignore_variant), Some(fallthrough))
-    };
-
     let visitor_impl = Stmts(deserialize_identifier(
         &this_value,
         fields,
@@ -2070,6 +2033,33 @@ fn deserialize_generated_identifier(
     }
 }
 
+/// Generates enum and its `Deserialize` implementation that represents each
+/// non-skipped field of the struct
+fn deserialize_field_identifier(
+    fields: &[(&str, Ident, &BTreeSet<String>)],
+    cattrs: &attr::Container,
+) -> Stmts {
+    let (ignore_variant, fallthrough) = if cattrs.has_flatten() {
+        let ignore_variant = quote!(__other(_serde::__private::de::Content<'de>),);
+        let fallthrough = quote!(_serde::__private::Ok(__Field::__other(__value)));
+        (Some(ignore_variant), Some(fallthrough))
+    } else if cattrs.deny_unknown_fields() {
+        (None, None)
+    } else {
+        let ignore_variant = quote!(__ignore,);
+        let fallthrough = quote!(_serde::__private::Ok(__Field::__ignore));
+        (Some(ignore_variant), Some(fallthrough))
+    };
+
+    Stmts(deserialize_generated_identifier(
+        fields,
+        cattrs,
+        false,
+        ignore_variant,
+        fallthrough,
+    ))
+}
+
 // Generates `Deserialize::deserialize` body for an enum with
 // `serde(field_identifier)` or `serde(variant_identifier)` attribute.
 fn deserialize_custom_identifier(
@@ -2131,7 +2121,7 @@ fn deserialize_custom_identifier(
         })
         .collect();
 
-    let names = names_idents.iter().map(|(name, _, _)| name);
+    let names = names_idents.iter().flat_map(|&(_, _, aliases)| aliases);
 
     let names_const = if fallthrough.is_some() {
         None
@@ -2187,32 +2177,24 @@ fn deserialize_custom_identifier(
 
 fn deserialize_identifier(
     this_value: &TokenStream,
-    fields: &[(String, Ident, Vec<String>)],
+    fields: &[(&str, Ident, &BTreeSet<String>)],
     is_variant: bool,
     fallthrough: Option<TokenStream>,
     fallthrough_borrowed: Option<TokenStream>,
     collect_other_fields: bool,
     expecting: Option<&str>,
 ) -> Fragment {
-    let mut flat_fields = Vec::new();
+    let str_mapping = fields.iter().map(|(_, ident, aliases)| {
-    for (_, ident, aliases) in fields {
+        // `aliases` also contains a main name
-        flat_fields.extend(aliases.iter().map(|alias| (alias, ident)));
+        quote!(#(#aliases)|* => _serde::__private::Ok(#this_value::#ident))
-    }
+    });
-
+    let bytes_mapping = fields.iter().map(|(_, ident, aliases)| {
-    let field_strs: &Vec<_> = &flat_fields.iter().map(|(name, _)| name).collect();
+        // `aliases` also contains a main name
-    let field_bytes: &Vec<_> = &flat_fields
+        let aliases = aliases
-        .iter()
+            .iter()
-        .map(|(name, _)| Literal::byte_string(name.as_bytes()))
+            .map(|alias| Literal::byte_string(alias.as_bytes()));
-        .collect();
+        quote!(#(#aliases)|* => _serde::__private::Ok(#this_value::#ident))
-
+    });
-    let constructors: &Vec<_> = &flat_fields
-        .iter()
-        .map(|(_, ident)| quote!(#this_value::#ident))
-        .collect();
-    let main_constructors: &Vec<_> = &fields
-        .iter()
-        .map(|(_, ident, _)| quote!(#this_value::#ident))
-        .collect();
 
     let expecting = expecting.unwrap_or(if is_variant {
         "variant identifier"
@@ -2220,8 +2202,6 @@ fn deserialize_identifier(
         "field identifier"
     });
 
-    let index_expecting = if is_variant { "variant" } else { "field" };
-
     let bytes_to_str = if fallthrough.is_some() || collect_other_fields {
         None
     } else {
@@ -2269,21 +2249,6 @@ fn deserialize_identifier(
         &fallthrough_arm_tokens
     };
 
-    let u64_fallthrough_arm_tokens;
-    let u64_fallthrough_arm = if let Some(fallthrough) = &fallthrough {
-        fallthrough
-    } else {
-        let fallthrough_msg = format!("{} index 0 <= i < {}", index_expecting, fields.len());
-        u64_fallthrough_arm_tokens = quote! {
-            _serde::__private::Err(_serde::de::Error::invalid_value(
-                _serde::de::Unexpected::Unsigned(__value),
-                &#fallthrough_msg,
-            ))
-        };
-        &u64_fallthrough_arm_tokens
-    };
-
-    let variant_indices = 0_u64..;
     let visit_other = if collect_other_fields {
         quote! {
             fn visit_bool<__E>(self, __value: bool) -> _serde::__private::Result<Self::Value, __E>
@@ -2378,15 +2343,33 @@ fn deserialize_identifier(
             }
         }
     } else {
+        let u64_mapping = fields.iter().enumerate().map(|(i, (_, ident, _))| {
+            let i = i as u64;
+            quote!(#i => _serde::__private::Ok(#this_value::#ident))
+        });
+
+        let u64_fallthrough_arm_tokens;
+        let u64_fallthrough_arm = if let Some(fallthrough) = &fallthrough {
+            fallthrough
+        } else {
+            let index_expecting = if is_variant { "variant" } else { "field" };
+            let fallthrough_msg = format!("{} index 0 <= i < {}", index_expecting, fields.len());
+            u64_fallthrough_arm_tokens = quote! {
+                _serde::__private::Err(_serde::de::Error::invalid_value(
+                    _serde::de::Unexpected::Unsigned(__value),
+                    &#fallthrough_msg,
+                ))
+            };
+            &u64_fallthrough_arm_tokens
+        };
+
         quote! {
             fn visit_u64<__E>(self, __value: u64) -> _serde::__private::Result<Self::Value, __E>
             where
                 __E: _serde::de::Error,
             {
                 match __value {
-                    #(
+                    #(#u64_mapping,)*
-                        #variant_indices => _serde::__private::Ok(#main_constructors),
-                    )*
                     _ => #u64_fallthrough_arm,
                 }
             }
@@ -2394,6 +2377,8 @@ fn deserialize_identifier(
     };
 
     let visit_borrowed = if fallthrough_borrowed.is_some() || collect_other_fields {
+        let str_mapping = str_mapping.clone();
+        let bytes_mapping = bytes_mapping.clone();
         let fallthrough_borrowed_arm = fallthrough_borrowed.as_ref().unwrap_or(fallthrough_arm);
         Some(quote! {
             fn visit_borrowed_str<__E>(self, __value: &'de str) -> _serde::__private::Result<Self::Value, __E>
@@ -2401,9 +2386,7 @@ fn deserialize_identifier(
                 __E: _serde::de::Error,
             {
                 match __value {
-                    #(
+                    #(#str_mapping,)*
-                        #field_strs => _serde::__private::Ok(#constructors),
-                    )*
                     _ => {
                         #value_as_borrowed_str_content
                         #fallthrough_borrowed_arm
@@ -2416,9 +2399,7 @@ fn deserialize_identifier(
                 __E: _serde::de::Error,
             {
                 match __value {
-                    #(
+                    #(#bytes_mapping,)*
-                        #field_bytes => _serde::__private::Ok(#constructors),
-                    )*
                     _ => {
                         #bytes_to_str
                         #value_as_borrowed_bytes_content
@@ -2443,9 +2424,7 @@ fn deserialize_identifier(
             __E: _serde::de::Error,
         {
             match __value {
-                #(
+                #(#str_mapping,)*
-                    #field_strs => _serde::__private::Ok(#constructors),
-                )*
                 _ => {
                     #value_as_str_content
                     #fallthrough_arm
@@ -2458,9 +2437,7 @@ fn deserialize_identifier(
             __E: _serde::de::Error,
         {
             match __value {
-                #(
+                #(#bytes_mapping,)*
-                    #field_bytes => _serde::__private::Ok(#constructors),
-                )*
                 _ => {
                     #bytes_to_str
                     #value_as_bytes_content
@@ -2993,6 +2970,35 @@ fn expr_is_missing(field: &Field, cattrs: &attr::Container) -> Fragment {
     }
 }
 
+fn expr_is_missing_seq(
+    assign_to: Option<TokenStream>,
+    index: usize,
+    field: &Field,
+    cattrs: &attr::Container,
+    expecting: &str,
+) -> TokenStream {
+    match field.attrs.default() {
+        attr::Default::Default => {
+            let span = field.original.span();
+            return quote_spanned!(span=> #assign_to _serde::__private::Default::default());
+        }
+        attr::Default::Path(path) => {
+            return quote_spanned!(path.span()=> #assign_to #path());
+        }
+        attr::Default::None => { /* below */ }
+    }
+
+    match *cattrs.default() {
+        attr::Default::Default | attr::Default::Path(_) => {
+            let member = &field.member;
+            quote!(#assign_to __default.#member)
+        }
+        attr::Default::None => quote!(
+            return _serde::__private::Err(_serde::de::Error::invalid_length(#index, &#expecting))
+        ),
+    }
+}
+
 fn effective_style(variant: &Variant) -> Style {
     match variant.style {
         Style::Newtype if variant.fields[0].attrs.skip_deserializing() => Style::Unit,

serde_derive/src/internals/attr.rs

@@ -134,7 +134,7 @@ pub struct Name {
     serialize_renamed: bool,
     deserialize: String,
     deserialize_renamed: bool,
-    deserialize_aliases: Vec<String>,
+    deserialize_aliases: BTreeSet<String>,
 }
 
 fn unraw(ident: &Ident) -> String {
@@ -148,16 +148,12 @@ impl Name {
         de_name: Attr<String>,
         de_aliases: Option<VecAttr<String>>,
     ) -> Name {
-        let deserialize_aliases = match de_aliases {
+        let mut alias_set = BTreeSet::new();
-            Some(de_aliases) => {
+        if let Some(de_aliases) = de_aliases {
-                let mut alias_list = BTreeSet::new();
+            for alias_name in de_aliases.get() {
-                for alias_name in de_aliases.get() {
+                alias_set.insert(alias_name);
-                    alias_list.insert(alias_name);
-                }
-                alias_list.into_iter().collect()
             }
-            None => Vec::new(),
+        }
-        };
 
         let ser_name = ser_name.get();
         let ser_renamed = ser_name.is_some();
@@ -168,27 +164,22 @@ impl Name {
             serialize_renamed: ser_renamed,
             deserialize: de_name.unwrap_or(source_name),
             deserialize_renamed: de_renamed,
-            deserialize_aliases,
+            deserialize_aliases: alias_set,
         }
     }
 
     /// Return the container name for the container when serializing.
-    pub fn serialize_name(&self) -> String {
+    pub fn serialize_name(&self) -> &str {
-        self.serialize.clone()
+        &self.serialize
     }
 
     /// Return the container name for the container when deserializing.
-    pub fn deserialize_name(&self) -> String {
+    pub fn deserialize_name(&self) -> &str {
-        self.deserialize.clone()
+        &self.deserialize
     }
 
-    fn deserialize_aliases(&self) -> Vec<String> {
+    fn deserialize_aliases(&self) -> &BTreeSet<String> {
-        let mut aliases = self.deserialize_aliases.clone();
+        &self.deserialize_aliases
-        let main_name = self.deserialize_name();
-        if !aliases.contains(&main_name) {
-            aliases.push(main_name);
-        }
-        aliases
     }
 }
 
@@ -405,20 +396,20 @@ impl Container {
                         if let Some(path) = parse_lit_into_expr_path(cx, DEFAULT, &meta)? {
                             match &item.data {
                                 syn::Data::Struct(syn::DataStruct { fields, .. }) => match fields {
-                                    syn::Fields::Named(_) => {
+                                    syn::Fields::Named(_) | syn::Fields::Unnamed(_) => {
                                         default.set(&meta.path, Default::Path(path));
                                     }
-                                    syn::Fields::Unnamed(_) | syn::Fields::Unit => {
+                                    syn::Fields::Unit => {
-                                        let msg = "#[serde(default = \"...\")] can only be used on structs with named fields";
+                                        let msg = "#[serde(default = \"...\")] can only be used on structs that have fields";
                                         cx.syn_error(meta.error(msg));
                                     }
                                 },
                                 syn::Data::Enum(_) => {
-                                    let msg = "#[serde(default = \"...\")] can only be used on structs with named fields";
+                                    let msg = "#[serde(default = \"...\")] can only be used on structs";
                                     cx.syn_error(meta.error(msg));
                                 }
                                 syn::Data::Union(_) => {
-                                    let msg = "#[serde(default = \"...\")] can only be used on structs with named fields";
+                                    let msg = "#[serde(default = \"...\")] can only be used on structs";
                                     cx.syn_error(meta.error(msg));
                                 }
                             }
@@ -427,20 +418,20 @@ impl Container {
                         // #[serde(default)]
                         match &item.data {
                             syn::Data::Struct(syn::DataStruct { fields, .. }) => match fields {
-                                syn::Fields::Named(_) => {
+                                syn::Fields::Named(_) | syn::Fields::Unnamed(_) => {
                                     default.set(meta.path, Default::Default);
                                 }
-                                syn::Fields::Unnamed(_) | syn::Fields::Unit => {
+                                syn::Fields::Unit => {
-                                    let msg = "#[serde(default)] can only be used on structs with named fields";
+                                    let msg = "#[serde(default)] can only be used on structs that have fields";
                                     cx.error_spanned_by(fields, msg);
                                 }
                             },
                             syn::Data::Enum(_) => {
-                                let msg = "#[serde(default)] can only be used on structs with named fields";
+                                let msg = "#[serde(default)] can only be used on structs";
                                 cx.syn_error(meta.error(msg));
                             }
                             syn::Data::Union(_) => {
-                                let msg = "#[serde(default)] can only be used on structs with named fields";
+                                let msg = "#[serde(default)] can only be used on structs";
                                 cx.syn_error(meta.error(msg));
                             }
                         }
@@ -977,7 +968,7 @@ impl Variant {
         &self.name
     }
 
-    pub fn aliases(&self) -> Vec<String> {
+    pub fn aliases(&self) -> &BTreeSet<String> {
         self.name.deserialize_aliases()
     }
 
@@ -988,6 +979,9 @@ impl Variant {
         if !self.name.deserialize_renamed {
             self.name.deserialize = rules.deserialize.apply_to_variant(&self.name.deserialize);
         }
+        self.name
+            .deserialize_aliases
+            .insert(self.name.deserialize.clone());
     }
 
     pub fn rename_all_rules(&self) -> RenameAllRules {
@@ -1316,7 +1310,7 @@ impl Field {
         &self.name
     }
 
-    pub fn aliases(&self) -> Vec<String> {
+    pub fn aliases(&self) -> &BTreeSet<String> {
         self.name.deserialize_aliases()
     }
 
@@ -1327,6 +1321,9 @@ impl Field {
         if !self.name.deserialize_renamed {
             self.name.deserialize = rules.deserialize.apply_to_field(&self.name.deserialize);
         }
+        self.name
+            .deserialize_aliases
+            .insert(self.name.deserialize.clone());
     }
 
     pub fn skip_serializing(&self) -> bool {

serde_derive/src/internals/check.rs

@@ -1,11 +1,12 @@
 use crate::internals::ast::{Container, Data, Field, Style};
-use crate::internals::attr::{Identifier, TagType};
+use crate::internals::attr::{Default, Identifier, TagType};
 use crate::internals::{ungroup, Ctxt, Derive};
 use syn::{Member, Type};
 
 // Cross-cutting checks that require looking at more than a single attrs object.
 // Simpler checks should happen when parsing and building the attrs.
 pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
+    check_default_on_tuple(cx, cont);
     check_remote_generic(cx, cont);
     check_getter(cx, cont);
     check_flatten(cx, cont);
@@ -17,6 +18,39 @@ pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
     check_from_and_try_from(cx, cont);
 }
 
+// If some field of a tuple struct is marked #[serde(default)] then all fields
+// after it must also be marked with that attribute, or the struct must have a
+// container-level serde(default) attribute. A field's default value is only
+// used for tuple fields if the sequence is exhausted at that point; that means
+// all subsequent fields will fail to deserialize if they don't have their own
+// default.
+fn check_default_on_tuple(cx: &Ctxt, cont: &Container) {
+    if let Default::None = cont.attrs.default() {
+        if let Data::Struct(Style::Tuple, fields) = &cont.data {
+            let mut first_default_index = None;
+            for (i, field) in fields.iter().enumerate() {
+                // Skipped fields automatically get the #[serde(default)]
+                // attribute. We are interested only on non-skipped fields here.
+                if field.attrs.skip_deserializing() {
+                    continue;
+                }
+                if let Default::None = field.attrs.default() {
+                    if let Some(first) = first_default_index {
+                        cx.error_spanned_by(
+                            field.ty,
+                            format!("field must have #[serde(default)] because previous field {} has #[serde(default)]", first),
+                        );
+                    }
+                    continue;
+                }
+                if first_default_index.is_none() {
+                    first_default_index = Some(i);
+                }
+            }
+        }
+    }
+}
+
 // Remote derive definition type must have either all of the generics of the
 // remote type:
 //

serde_derive/src/lib.rs

@@ -13,7 +13,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.181")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.183")]
 // Ignored clippy lints
 #![allow(
     // clippy false positive: https://github.com/rust-lang/rust-clippy/issues/7054

serde_derive/src/ser.rs

@@ -566,7 +566,7 @@ fn serialize_externally_tagged_variant(
             },
             params,
             &variant.fields,
-            &type_name,
+            type_name,
         ),
     }
 }
@@ -631,7 +631,7 @@ fn serialize_internally_tagged_variant(
             StructVariant::InternallyTagged { tag, variant_name },
             params,
             &variant.fields,
-            &type_name,
+            type_name,
         ),
         Style::Tuple => unreachable!("checked in serde_derive_internals"),
     }
@@ -698,7 +698,7 @@ fn serialize_adjacently_tagged_variant(
                 StructVariant::Untagged,
                 params,
                 &variant.fields,
-                &variant_name,
+                variant_name,
             ),
         }
     });
@@ -794,16 +794,16 @@ fn serialize_untagged_variant(
         Style::Tuple => serialize_tuple_variant(TupleVariant::Untagged, params, &variant.fields),
         Style::Struct => {
             let type_name = cattrs.name().serialize_name();
-            serialize_struct_variant(StructVariant::Untagged, params, &variant.fields, &type_name)
+            serialize_struct_variant(StructVariant::Untagged, params, &variant.fields, type_name)
         }
     }
 }
 
-enum TupleVariant {
+enum TupleVariant<'a> {
     ExternallyTagged {
-        type_name: String,
+        type_name: &'a str,
         variant_index: u32,
-        variant_name: String,
+        variant_name: &'a str,
     },
     Untagged,
 }
@@ -870,11 +870,11 @@ fn serialize_tuple_variant(
 enum StructVariant<'a> {
     ExternallyTagged {
         variant_index: u32,
-        variant_name: String,
+        variant_name: &'a str,
     },
     InternallyTagged {
         tag: &'a str,
-        variant_name: String,
+        variant_name: &'a str,
     },
     Untagged,
 }

test_suite/no_std/src/main.rs

@@ -1,3 +1,4 @@
+#![allow(internal_features)]
 #![feature(lang_items, start)]
 #![no_std]
 

test_suite/tests/test_annotations.rs

@@ -605,7 +605,7 @@ fn test_unknown_field_rename_struct() {
             Token::Str("a4"),
             Token::I32(3),
         ],
-        "unknown field `a4`, expected one of `a1`, `a3`, `a2`, `a5`, `a6`",
+        "unknown field `a4`, expected one of `a1`, `a2`, `a3`, `a5`, `a6`",
     );
 }
 
@@ -799,7 +799,7 @@ fn test_unknown_field_rename_enum() {
             Token::Str("d"),
             Token::I8(2),
         ],
-        "unknown field `d`, expected one of `a`, `c`, `b`, `e`, `f`",
+        "unknown field `d`, expected one of `a`, `b`, `c`, `e`, `f`",
     );
 }
 

test_suite/tests/test_identifier.rs

@@ -3,86 +3,186 @@
 #![allow(clippy::derive_partial_eq_without_eq)]
 
 use serde_derive::Deserialize;
-use serde_test::{assert_de_tokens, Token};
+use serde_test::{assert_de_tokens, assert_de_tokens_error, Token};
+
+mod variant_identifier {
+    use super::*;
 
-#[test]
-fn test_variant_identifier() {
     #[derive(Deserialize, Debug, PartialEq)]
     #[serde(variant_identifier)]
     enum V {
         Aaa,
+        #[serde(alias = "Ccc", alias = "Ddd")]
         Bbb,
     }
 
-    assert_de_tokens(&V::Aaa, &[Token::U8(0)]);
+    #[test]
-    assert_de_tokens(&V::Aaa, &[Token::U16(0)]);
+    fn variant1() {
-    assert_de_tokens(&V::Aaa, &[Token::U32(0)]);
+        assert_de_tokens(&V::Aaa, &[Token::U8(0)]);
-    assert_de_tokens(&V::Aaa, &[Token::U64(0)]);
+        assert_de_tokens(&V::Aaa, &[Token::U16(0)]);
-    assert_de_tokens(&V::Aaa, &[Token::Str("Aaa")]);
+        assert_de_tokens(&V::Aaa, &[Token::U32(0)]);
-    assert_de_tokens(&V::Aaa, &[Token::Bytes(b"Aaa")]);
+        assert_de_tokens(&V::Aaa, &[Token::U64(0)]);
+        assert_de_tokens(&V::Aaa, &[Token::Str("Aaa")]);
+        assert_de_tokens(&V::Aaa, &[Token::Bytes(b"Aaa")]);
+    }
+
+    #[test]
+    fn aliases() {
+        assert_de_tokens(&V::Bbb, &[Token::U8(1)]);
+        assert_de_tokens(&V::Bbb, &[Token::U16(1)]);
+        assert_de_tokens(&V::Bbb, &[Token::U32(1)]);
+        assert_de_tokens(&V::Bbb, &[Token::U64(1)]);
+
+        assert_de_tokens(&V::Bbb, &[Token::Str("Bbb")]);
+        assert_de_tokens(&V::Bbb, &[Token::Bytes(b"Bbb")]);
+
+        assert_de_tokens(&V::Bbb, &[Token::Str("Ccc")]);
+        assert_de_tokens(&V::Bbb, &[Token::Bytes(b"Ccc")]);
+
+        assert_de_tokens(&V::Bbb, &[Token::Str("Ddd")]);
+        assert_de_tokens(&V::Bbb, &[Token::Bytes(b"Ddd")]);
+    }
+
+    #[test]
+    fn unknown() {
+        assert_de_tokens_error::<V>(
+            &[Token::U8(42)],
+            "invalid value: integer `42`, expected variant index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<V>(
+            &[Token::U16(42)],
+            "invalid value: integer `42`, expected variant index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<V>(
+            &[Token::U32(42)],
+            "invalid value: integer `42`, expected variant index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<V>(
+            &[Token::U64(42)],
+            "invalid value: integer `42`, expected variant index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<V>(
+            &[Token::Str("Unknown")],
+            "unknown variant `Unknown`, expected one of `Aaa`, `Bbb`, `Ccc`, `Ddd`",
+        );
+        assert_de_tokens_error::<V>(
+            &[Token::Bytes(b"Unknown")],
+            "unknown variant `Unknown`, expected one of `Aaa`, `Bbb`, `Ccc`, `Ddd`",
+        );
+    }
 }
 
-#[test]
+mod field_identifier {
-fn test_field_identifier() {
+    use super::*;
+
     #[derive(Deserialize, Debug, PartialEq)]
     #[serde(field_identifier, rename_all = "snake_case")]
     enum F {
         Aaa,
+        #[serde(alias = "ccc", alias = "ddd")]
         Bbb,
     }
 
-    assert_de_tokens(&F::Aaa, &[Token::U8(0)]);
+    #[test]
-    assert_de_tokens(&F::Aaa, &[Token::U16(0)]);
+    fn field1() {
-    assert_de_tokens(&F::Aaa, &[Token::U32(0)]);
+        assert_de_tokens(&F::Aaa, &[Token::U8(0)]);
-    assert_de_tokens(&F::Aaa, &[Token::U64(0)]);
+        assert_de_tokens(&F::Aaa, &[Token::U16(0)]);
-    assert_de_tokens(&F::Aaa, &[Token::Str("aaa")]);
+        assert_de_tokens(&F::Aaa, &[Token::U32(0)]);
-    assert_de_tokens(&F::Aaa, &[Token::Bytes(b"aaa")]);
+        assert_de_tokens(&F::Aaa, &[Token::U64(0)]);
-}
+        assert_de_tokens(&F::Aaa, &[Token::Str("aaa")]);
-
+        assert_de_tokens(&F::Aaa, &[Token::Bytes(b"aaa")]);
-#[test]
-fn test_unit_fallthrough() {
-    #[derive(Deserialize, Debug, PartialEq)]
-    #[serde(field_identifier, rename_all = "snake_case")]
-    enum F {
-        Aaa,
-        Bbb,
-        #[serde(other)]
-        Other,
     }
 
-    assert_de_tokens(&F::Other, &[Token::U8(42)]);
+    #[test]
-    assert_de_tokens(&F::Other, &[Token::U16(42)]);
+    fn aliases() {
-    assert_de_tokens(&F::Other, &[Token::U32(42)]);
+        assert_de_tokens(&F::Bbb, &[Token::U8(1)]);
-    assert_de_tokens(&F::Other, &[Token::U64(42)]);
+        assert_de_tokens(&F::Bbb, &[Token::U16(1)]);
-    assert_de_tokens(&F::Other, &[Token::Str("x")]);
+        assert_de_tokens(&F::Bbb, &[Token::U32(1)]);
-}
+        assert_de_tokens(&F::Bbb, &[Token::U64(1)]);
 
-#[test]
+        assert_de_tokens(&F::Bbb, &[Token::Str("bbb")]);
-fn test_newtype_fallthrough() {
+        assert_de_tokens(&F::Bbb, &[Token::Bytes(b"bbb")]);
-    #[derive(Deserialize, Debug, PartialEq)]
+
-    #[serde(field_identifier, rename_all = "snake_case")]
+        assert_de_tokens(&F::Bbb, &[Token::Str("ccc")]);
-    enum F {
+        assert_de_tokens(&F::Bbb, &[Token::Bytes(b"ccc")]);
-        Aaa,
+
-        Bbb,
+        assert_de_tokens(&F::Bbb, &[Token::Str("ddd")]);
-        Other(String),
+        assert_de_tokens(&F::Bbb, &[Token::Bytes(b"ddd")]);
     }
 
-    assert_de_tokens(&F::Other("x".to_owned()), &[Token::Str("x")]);
+    #[test]
-}
+    fn unknown() {
-
+        assert_de_tokens_error::<F>(
-#[test]
+            &[Token::U8(42)],
-fn test_newtype_fallthrough_generic() {
+            "invalid value: integer `42`, expected field index 0 <= i < 2",
-    #[derive(Deserialize, Debug, PartialEq)]
+        );
-    #[serde(field_identifier, rename_all = "snake_case")]
+        assert_de_tokens_error::<F>(
-    enum F<T> {
+            &[Token::U16(42)],
-        Aaa,
+            "invalid value: integer `42`, expected field index 0 <= i < 2",
-        Bbb,
+        );
-        Other(T),
+        assert_de_tokens_error::<F>(
+            &[Token::U32(42)],
+            "invalid value: integer `42`, expected field index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<F>(
+            &[Token::U64(42)],
+            "invalid value: integer `42`, expected field index 0 <= i < 2",
+        );
+        assert_de_tokens_error::<F>(
+            &[Token::Str("unknown")],
+            "unknown field `unknown`, expected one of `aaa`, `bbb`, `ccc`, `ddd`",
+        );
+        assert_de_tokens_error::<F>(
+            &[Token::Bytes(b"unknown")],
+            "unknown field `unknown`, expected one of `aaa`, `bbb`, `ccc`, `ddd`",
+        );
     }
 
-    assert_de_tokens(&F::Other(42u8), &[Token::U8(42)]);
+    #[test]
-    assert_de_tokens(&F::Other(42u16), &[Token::U16(42)]);
+    fn unit_fallthrough() {
-    assert_de_tokens(&F::Other(42u32), &[Token::U32(42)]);
+        #[derive(Deserialize, Debug, PartialEq)]
-    assert_de_tokens(&F::Other(42u64), &[Token::U64(42)]);
+        #[serde(field_identifier, rename_all = "snake_case")]
-    assert_de_tokens(&F::Other("x".to_owned()), &[Token::Str("x")]);
+        enum F {
+            Aaa,
+            Bbb,
+            #[serde(other)]
+            Other,
+        }
+
+        assert_de_tokens(&F::Other, &[Token::U8(42)]);
+        assert_de_tokens(&F::Other, &[Token::U16(42)]);
+        assert_de_tokens(&F::Other, &[Token::U32(42)]);
+        assert_de_tokens(&F::Other, &[Token::U64(42)]);
+        assert_de_tokens(&F::Other, &[Token::Str("x")]);
+    }
+
+    #[test]
+    fn newtype_fallthrough() {
+        #[derive(Deserialize, Debug, PartialEq)]
+        #[serde(field_identifier, rename_all = "snake_case")]
+        enum F {
+            Aaa,
+            Bbb,
+            Other(String),
+        }
+
+        assert_de_tokens(&F::Other("x".to_owned()), &[Token::Str("x")]);
+    }
+
+    #[test]
+    fn newtype_fallthrough_generic() {
+        #[derive(Deserialize, Debug, PartialEq)]
+        #[serde(field_identifier, rename_all = "snake_case")]
+        enum F<T> {
+            Aaa,
+            Bbb,
+            Other(T),
+        }
+
+        assert_de_tokens(&F::Other(42u8), &[Token::U8(42)]);
+        assert_de_tokens(&F::Other(42u16), &[Token::U16(42)]);
+        assert_de_tokens(&F::Other(42u32), &[Token::U32(42)]);
+        assert_de_tokens(&F::Other(42u64), &[Token::U64(42)]);
+        assert_de_tokens(&F::Other("x".to_owned()), &[Token::Str("x")]);
+    }
 }

test_suite/tests/ui/default-attribute/enum.stderr

@@ -1,4 +1,4 @@
-error: #[serde(default)] can only be used on structs with named fields
+error: #[serde(default)] can only be used on structs
  --> tests/ui/default-attribute/enum.rs:4:9
   |
 4 | #[serde(default)]

test_suite/tests/ui/default-attribute/enum_path.stderr

@@ -1,4 +1,4 @@
-error: #[serde(default = "...")] can only be used on structs with named fields
+error: #[serde(default = "...")] can only be used on structs
  --> tests/ui/default-attribute/enum_path.rs:4:9
   |
 4 | #[serde(default = "default_e")]

test_suite/tests/ui/default-attribute/nameless_struct_fields.rs

@@ -1,7 +0,0 @@
-use serde_derive::Deserialize;
-
-#[derive(Deserialize)]
-#[serde(default)]
-struct T(u8, u8);
-
-fn main() {}

test_suite/tests/ui/default-attribute/nameless_struct_fields.stderr

@@ -1,5 +0,0 @@
-error: #[serde(default)] can only be used on structs with named fields
- --> tests/ui/default-attribute/nameless_struct_fields.rs:5:9
-  |
-5 | struct T(u8, u8);
-  |         ^^^^^^^^

test_suite/tests/ui/default-attribute/nameless_struct_fields_path.rs

@@ -1,7 +0,0 @@
-use serde_derive::Deserialize;
-
-#[derive(Deserialize)]
-#[serde(default = "default_t")]
-struct T(u8, u8);
-
-fn main() {}

test_suite/tests/ui/default-attribute/nameless_struct_fields_path.stderr

@@ -1,5 +0,0 @@
-error: #[serde(default = "...")] can only be used on structs with named fields
- --> tests/ui/default-attribute/nameless_struct_fields_path.rs:4:9
-  |
-4 | #[serde(default = "default_t")]
-  |         ^^^^^^^^^^^^^^^^^^^^^

test_suite/tests/ui/default-attribute/tuple_struct.rs

@@ -0,0 +1,47 @@
+use serde_derive::Deserialize;
+
+// No errors expected.
+#[derive(Deserialize)]
+struct T0(u8, u8);
+
+// No errors expected:
+// - If both fields are provided, both get value from data.
+// - If only one field is provided, the second gets default value.
+#[derive(Deserialize)]
+struct T1(u8, #[serde(default)] u8);
+
+// ERROR: The first field can get default value only if sequence is empty, but
+// that mean that all other fields cannot be deserialized without errors.
+#[derive(Deserialize)]
+struct T2(#[serde(default)] u8, u8, u8);
+
+// No errors expected:
+// - If both fields are provided, both get value from data.
+// - If only one field is provided, the second gets default value.
+// - If no fields are provided, both get default value.
+#[derive(Deserialize)]
+struct T3(#[serde(default)] u8, #[serde(default)] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T4(u8, u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T5(#[serde(default)] u8, u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T6(u8, #[serde(default)] u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T7(#[serde(default)] u8, #[serde(default)] u8);
+
+fn main() {}

test_suite/tests/ui/default-attribute/tuple_struct.stderr

@@ -0,0 +1,11 @@
+error: field must have #[serde(default)] because previous field 0 has #[serde(default)]
+  --> tests/ui/default-attribute/tuple_struct.rs:16:33
+   |
+16 | struct T2(#[serde(default)] u8, u8, u8);
+   |                                 ^^
+
+error: field must have #[serde(default)] because previous field 0 has #[serde(default)]
+  --> tests/ui/default-attribute/tuple_struct.rs:16:37
+   |
+16 | struct T2(#[serde(default)] u8, u8, u8);
+   |                                     ^^

test_suite/tests/ui/default-attribute/tuple_struct_path.rs

@@ -0,0 +1,76 @@
+use serde_derive::Deserialize;
+
+fn d<T>() -> T {
+    unimplemented!()
+}
+
+// No errors expected:
+// - If both fields are provided, both get value from data.
+// - If only one field is provided, the second gets default value.
+#[derive(Deserialize)]
+struct T1(u8, #[serde(default = "d")] u8);
+
+// ERROR: The first field can get default value only if sequence is empty, but
+// that mean that all other fields cannot be deserialized without errors.
+#[derive(Deserialize)]
+struct T2(#[serde(default = "d")] u8, u8, u8);
+
+// No errors expected:
+// - If both fields are provided, both get value from data.
+// - If only one field is provided, the second gets default value.
+// - If no fields are provided, both get default value.
+#[derive(Deserialize)]
+struct T3(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T1D(#[serde(default = "d")] u8, u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T2D(u8, #[serde(default = "d")] u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize, Default)]
+#[serde(default)]
+struct T3D(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T1Path(#[serde(default)] u8, u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T2Path(u8, #[serde(default)] u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T3Path(#[serde(default)] u8, #[serde(default)] u8);
+
+////////////////////////////////////////////////////////////////////////////////
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T1PathD(#[serde(default = "d")] u8, u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T2PathD(u8, #[serde(default = "d")] u8);
+
+// No errors expected -- missing fields get default values.
+#[derive(Deserialize)]
+#[serde(default = "d")]
+struct T3PathD(#[serde(default = "d")] u8, #[serde(default = "d")] u8);
+
+fn main() {}

test_suite/tests/ui/default-attribute/tuple_struct_path.stderr

@@ -0,0 +1,11 @@
+error: field must have #[serde(default)] because previous field 0 has #[serde(default)]
+  --> tests/ui/default-attribute/tuple_struct_path.rs:16:39
+   |
+16 | struct T2(#[serde(default = "d")] u8, u8, u8);
+   |                                       ^^
+
+error: field must have #[serde(default)] because previous field 0 has #[serde(default)]
+  --> tests/ui/default-attribute/tuple_struct_path.rs:16:43
+   |
+16 | struct T2(#[serde(default = "d")] u8, u8, u8);
+   |                                           ^^