Use indices for fields and variants when that option is enabled.

serde-diff-derive/src/serde_diff/mod.rs

@@ -77,7 +77,7 @@ fn generate_fields_diff(
         let right = format_ident!("r{}", field_idx);
 
         let push = if let Some(_) = ident {
-            quote!{ctx.push_field(#ident_as_str);}
+            quote!{ctx.push_field(#field_idx, #ident_as_str);}
         } else {
             quote!{ctx.push_field_index(#field_idx);}
         };
@@ -170,7 +170,7 @@ fn ok_fields(fields : &syn::Fields) -> Result<Vec<ParsedField>, proc_macro::Toke
     }
 }
 
-fn generate_arms(name: &syn::Ident, variant: Option<&syn::Ident>, fields: &syn::Fields, matching: bool)
+fn generate_arms(name: &syn::Ident, variant: Option<(u16, &syn::Ident)>, fields: &syn::Fields, matching: bool)
                  -> Result<(Vec<proc_macro2::TokenStream>, Vec<proc_macro2::TokenStream>),
                            proc_macro2::TokenStream>
 {
@@ -182,14 +182,15 @@ fn generate_arms(name: &syn::Ident, variant: Option<&syn::Ident>, fields: &syn::
         matching,
     );                    
     let (left, right) =  enum_fields(&fields, false);
-    let variant_specifier = if let Some(id) = variant {
+    let variant_specifier = if let Some((_, id)) = variant {
         quote!{ :: #id}
     } else {
         quote!{}
     };
 
-    let variant_as_str = variant.map(|i| i.to_string());
-    let push_variant = variant.map(|_| quote!{ctx.push_variant(#variant_as_str);});
+    let variant_idx = variant.map(|(i, _)| i);
+    let variant_as_str = variant.map(|(_, i)| i.to_string());
+    let push_variant = variant.map(|_| quote!{ctx.push_variant(#variant_idx, #variant_as_str);});
     let pop_variant = variant.map(|_| quote!{ctx.pop_path_element()?;});
 
     let left = if matching {
@@ -259,6 +260,16 @@ fn generate_arms(name: &syn::Ident, variant: Option<&syn::Ident>, fields: &syn::
         }
 
         if let Some(_) = variant {
+            apply_match_arms.push(quote!{
+                ( &mut #name #variant_specifier #left, Some(serde_diff::DiffPathElementValue::EnumVariantIndex(#variant_idx))) => {
+                    while let Some(element) = ctx.next_path_element(seq)? {
+                        match element {
+                            #(#apply_fn_field_handlers)* 
+                            _ =>  ctx.skip_value(seq)?
+                        }
+                    }
+                }
+            });
             apply_match_arms.push(quote!{
                 ( &mut #name #variant_specifier #left, Some(serde_diff::DiffPathElementValue::EnumVariant(variant))) if variant == #variant_as_str => {
                     while let Some(element) = ctx.next_path_element(seq)? {
@@ -299,8 +310,8 @@ fn generate(
     let has_variants = match &input.data {
         Data::Enum(e) => {
             for matching in &[true, false] {
-                for v in &e.variants {
-                    let (diff, apply) = generate_arms(&struct_args.ident, Some(&v.ident), &v.fields, *matching)?;
+                for (i, v) in e.variants.iter().enumerate() {
+                    let (diff, apply) = generate_arms(&struct_args.ident, Some((i as u16, &v.ident)), &v.fields, *matching)?;
                     diff_match_arms.extend(diff);
                     apply_match_arms.extend(apply);
                 }

src/difference.rs

@@ -58,21 +58,38 @@ impl<'a, S: SerializeSeq> DiffContext<'a, S> {
     /// Called when we visit a field. If the structure is recursive (i.e. struct within struct,
     /// elements within an array) this may be called more than once before a corresponding pop_path_element
     /// is called. See `pop_path_element`
-    pub fn push_field(&mut self, field_name: &'static str) {
-        self.element_stack
-            .as_mut()
-            .unwrap()
-            .push(ElementStackEntry::PathElement(DiffPathElementValue::Field(
-                Cow::Borrowed(field_name),
-            )));
+    pub fn push_field(&mut self, field_idx: u16, field_name: &'static str) {
+        if matches!(self.field_path_mode, FieldPathMode::Index) {
+            self.push_field_index(field_idx);
+        } else {
+            self.element_stack
+                .as_mut()
+                .unwrap()
+                .push(ElementStackEntry::PathElement(DiffPathElementValue::Field(
+                    Cow::Borrowed(field_name),
+                )));
+        }
+    }
+
+    pub fn push_variant(&mut self, variant_idx: u16, variant_name: &'static str) {
+        if matches!(self.field_path_mode, FieldPathMode::Index) {
+            self.push_variant_index(variant_idx);
+        } else {
+            self.element_stack
+                .as_mut()
+                .unwrap()
+                .push(ElementStackEntry::PathElement(
+                    DiffPathElementValue::EnumVariant(Cow::Borrowed(variant_name)),
+                ));
+        }
     }
 
-    pub fn push_variant(&mut self, variant_name: &'static str) {
+    pub fn push_variant_index(&mut self, variant_idx: u16) {
         self.element_stack
             .as_mut()
             .unwrap()
             .push(ElementStackEntry::PathElement(
-                DiffPathElementValue::EnumVariant(Cow::Borrowed(variant_name)),
+                DiffPathElementValue::EnumVariantIndex(variant_idx),
             ));
     }
 
@@ -601,6 +618,7 @@ pub enum DiffPathElementValue<'a> {
     Field(Cow<'a, str>),
     FieldIndex(u16),
     EnumVariant(Cow<'a, str>),
+    EnumVariantIndex(u16),
     FullEnumVariant,
     CollectionIndex(usize),
     AddToCollection,

src/implementation.rs

@@ -96,7 +96,7 @@ macro_rules! tuple_impls {
                 ) -> Result<bool, S::Error> {
                     let mut changed = false;
                     $(
-                        ctx.push_field(stringify!($n));
+                        ctx.push_field_index($n);
                         changed |= <$name as $crate::SerdeDiff>::diff(&self.$n, ctx, &other.$n)?;
                         ctx.pop_path_element()?;
                     )+
@@ -112,10 +112,10 @@ macro_rules! tuple_impls {
                     A: serde::de::SeqAccess<'de>,
                 {
                     let mut changed = false;
-                    while let Some($crate::difference::DiffPathElementValue::Field(element)) = ctx.next_path_element(seq)? {
-                        match element.as_ref() {
+                    while let Some($crate::difference::DiffPathElementValue::FieldIndex(element)) = ctx.next_path_element(seq)? {
+                        match element {
                             $(
-                                stringify!($n) => changed |= <$name as $crate::SerdeDiff>::apply(&mut self.$n, seq, ctx)?,
+                                $n => changed |= <$name as $crate::SerdeDiff>::apply(&mut self.$n, seq, ctx)?,
                             )+
                             _ => ctx.skip_value(seq)?,
                         }