Merge pull request #4179 from epage/attr

refactor(derive): Prepare for builder attributes

CHANGELOG.md

@@ -55,7 +55,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - *(derive)* Changed the default for arguments from `parse` to `value_parser`., removing `parse` support
 - *(derive)* `subcommand_required(true).arg_required_else_help(true)` is set instead of `SubcommandRequiredElseHelp` (#3280)
 - *(derive)* Remove `arg_enum` attribute in favor of `value_enum`
-- *(derive)* Remove `structopt()` attributes in favor of `clap()`
 
 ### Compatibility
 

clap_derive/src/attr.rs

@@ -5,6 +5,7 @@ use proc_macro_error::abort;
 use proc_macro_error::ResultExt;
 use quote::quote;
 use quote::ToTokens;
+use syn::spanned::Spanned;
 use syn::{
     parenthesized,
     parse::{Parse, ParseStream},
@@ -12,8 +13,11 @@ use syn::{
     Attribute, Expr, Ident, LitStr, Token,
 };
 
+use crate::utils::Sp;
+
 #[derive(Clone)]
 pub struct ClapAttr {
+    pub kind: Sp<AttrKind>,
     pub name: Ident,
     pub magic: Option<MagicAttrName>,
     pub value: Option<AttrValue>,
@@ -23,10 +27,24 @@ impl ClapAttr {
     pub fn parse_all(all_attrs: &[Attribute]) -> Vec<Self> {
         all_attrs
             .iter()
-            .filter(|attr| attr.path.is_ident("clap"))
+            .filter_map(|attr| {
-            .flat_map(|attr| {
+                let kind = if attr.path.is_ident("clap") {
+                    Some(Sp::new(AttrKind::Clap, attr.path.span()))
+                } else if attr.path.is_ident("structopt") {
+                    Some(Sp::new(AttrKind::StructOpt, attr.path.span()))
+                } else {
+                    None
+                };
+                kind.map(|k| (k, attr))
+            })
+            .flat_map(|(k, attr)| {
                 attr.parse_args_with(Punctuated::<ClapAttr, Token![,]>::parse_terminated)
                     .unwrap_or_abort()
+                    .into_iter()
+                    .map(move |mut a| {
+                        a.kind = k;
+                        a
+                    })
             })
             .collect()
     }
@@ -113,7 +131,12 @@ impl Parse for ClapAttr {
             None
         };
 
-        Ok(Self { name, magic, value })
+        Ok(Self {
+            kind: Sp::new(AttrKind::Clap, name.span()),
+            name,
+            magic,
+            value,
+        })
     }
 }
 
@@ -166,3 +189,18 @@ impl ToTokens for AttrValue {
         }
     }
 }
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum AttrKind {
+    Clap,
+    StructOpt,
+}
+
+impl AttrKind {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            Self::Clap => "clap",
+            Self::StructOpt => "structopt",
+        }
+    }
+}

clap_derive/src/derives/args.rs

@@ -72,6 +72,13 @@ pub fn gen_for_struct(
     generics: &Generics,
     fields: &[(&Field, Item)],
 ) -> TokenStream {
+    if !matches!(&*item.kind(), Kind::Command(_)) {
+        abort! { item.kind().span(),
+            "`{}` cannot be used with `command`",
+            item.kind().name(),
+        }
+    }
+
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
     let constructor = gen_constructor(fields);
@@ -194,7 +201,9 @@ pub fn gen_augment(
     let args = fields.iter().filter_map(|(field, item)| {
         let kind = item.kind();
         match &*kind {
-            Kind::Subcommand(_)
+            Kind::Command(_)
+            | Kind::Value(_)
+            | Kind::Subcommand(_)
             | Kind::Skip(_)
             | Kind::FromGlobal(_)
             | Kind::ExternalSubcommand => None,
@@ -291,9 +300,16 @@ pub fn gen_augment(
 
                 let id = item.id();
                 let explicit_methods = item.field_methods(true);
+                let deprecations = if !override_required {
+                    item.deprecations()
+                } else {
+                    quote!()
+                };
 
                 Some(quote_spanned! { field.span()=>
                     let #app_var = #app_var.arg({
+                        #deprecations
+
                         #[allow(deprecated)]
                         let arg = clap::Arg::new(#id)
                             #implicit_methods;
@@ -307,9 +323,15 @@ pub fn gen_augment(
         }
     });
 
+    let deprecations = if !override_required {
+        parent_item.deprecations()
+    } else {
+        quote!()
+    };
     let initial_app_methods = parent_item.initial_top_level_methods();
     let final_app_methods = parent_item.final_top_level_methods();
     quote! {{
+        #deprecations
         let #app_var = #app_var #initial_app_methods;
         #( #args )*
         #subcmd
@@ -323,9 +345,12 @@ pub fn gen_constructor(fields: &[(&Field, Item)]) -> TokenStream {
         let kind = item.kind();
         let arg_matches = format_ident!("__clap_arg_matches");
         match &*kind {
-            Kind::ExternalSubcommand => {
+            Kind::Command(_)
+            | Kind::Value(_)
+            | Kind::ExternalSubcommand => {
                 abort! { kind.span(),
-                    "`external_subcommand` can be used only on enum variants"
+                    "`{}` cannot be used with `arg`",
+                    kind.name(),
                 }
             }
             Kind::Subcommand(ty) => {
@@ -391,9 +416,12 @@ pub fn gen_updater(fields: &[(&Field, Item)], use_self: bool) -> TokenStream {
         let arg_matches = format_ident!("__clap_arg_matches");
 
         match &*kind {
-            Kind::ExternalSubcommand => {
+            Kind::Command(_)
+            | Kind::Value(_)
+            | Kind::ExternalSubcommand => {
                 abort! { kind.span(),
-                    "`external_subcommand` can be used only on enum variants"
+                    "`{}` cannot be used with `arg`",
+                    kind.name(),
                 }
             }
             Kind::Subcommand(ty) => {

clap_derive/src/derives/subcommand.rs

@@ -52,6 +52,13 @@ pub fn gen_for_enum(
     generics: &Generics,
     variants: &[(&Variant, Item)],
 ) -> TokenStream {
+    if !matches!(&*item.kind(), Kind::Command(_)) {
+        abort! { item.kind().span(),
+            "`{}` cannot be used with `command`",
+            item.kind().name(),
+        }
+    }
+
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
     let from_arg_matches = gen_from_arg_matches(variants);
@@ -143,9 +150,15 @@ fn gen_augment(
                              or `Vec<OsString>`."
                         ),
                     };
+                    let deprecations = if !override_required {
+                        item.deprecations()
+                    } else {
+                        quote!()
+                    };
                     let subcommand = match subty_if_name(ty, "Vec") {
                         Some(subty) => {
                             quote_spanned! { kind.span()=>
+                                #deprecations
                                 let #app_var = #app_var.external_subcommand_value_parser(clap::value_parser!(#subty));
                             }
                         }
@@ -162,11 +175,17 @@ fn gen_augment(
                 Kind::Flatten => match variant.fields {
                     Unnamed(FieldsUnnamed { ref unnamed, .. }) if unnamed.len() == 1 => {
                         let ty = &unnamed[0];
+                        let deprecations = if !override_required {
+                            item.deprecations()
+                        } else {
+                            quote!()
+                        };
                         let old_heading_var = format_ident!("__clap_old_heading");
                         let next_help_heading = item.next_help_heading();
                         let next_display_order = item.next_display_order();
                         let subcommand = if override_required {
                             quote! {
+                                #deprecations
                                 let #old_heading_var = #app_var.get_next_help_heading().map(|s| clap::builder::Str::from(s.to_owned()));
                                 let #app_var = #app_var #next_help_heading #next_display_order;
                                 let #app_var = <#ty as clap::Subcommand>::augment_subcommands_for_update(#app_var);
@@ -174,6 +193,7 @@ fn gen_augment(
                             }
                         } else {
                             quote! {
+                                #deprecations
                                 let #old_heading_var = #app_var.get_next_help_heading().map(|s| clap::builder::Str::from(s.to_owned()));
                                 let #app_var = #app_var #next_help_heading #next_display_order;
                                 let #app_var = <#ty as clap::Subcommand>::augment_subcommands(#app_var);
@@ -217,10 +237,16 @@ fn gen_augment(
                     };
 
                     let name = item.cased_name();
+                    let deprecations = if !override_required {
+                        item.deprecations()
+                    } else {
+                        quote!()
+                    };
                     let initial_app_methods = item.initial_top_level_methods();
                     let final_from_attrs = item.final_top_level_methods();
                     let subcommand = quote! {
                         let #app_var = #app_var.subcommand({
+                            #deprecations;
                             let #subcommand_var = clap::Command::new(#name);
                             let #subcommand_var = #subcommand_var #initial_app_methods;
                             let #subcommand_var = #arg_block;
@@ -286,9 +312,15 @@ fn gen_augment(
                         }
                     };
 
+                    let deprecations = if !override_required {
+                        item.deprecations()
+                    } else {
+                        quote!()
+                    };
                     let name = item.cased_name();
                     let subcommand = quote! {
                         let #app_var = #app_var.subcommand({
+                            #deprecations
                             let #subcommand_var = clap::Command::new(#name);
                             #sub_augment
                         });
@@ -299,9 +331,15 @@ fn gen_augment(
         })
         .collect();
 
+    let deprecations = if !override_required {
+        parent_item.deprecations()
+    } else {
+        quote!()
+    };
     let initial_app_methods = parent_item.initial_top_level_methods();
     let final_app_methods = parent_item.final_top_level_methods();
     quote! {
+        #deprecations;
         let #app_var = #app_var #initial_app_methods;
         #( #subcommands )*;
         #app_var #final_app_methods

clap_derive/src/derives/value_enum.rs

@@ -41,10 +41,17 @@ pub fn derive_value_enum(input: &DeriveInput) -> TokenStream {
     }
 }
 
-pub fn gen_for_enum(_item: &Item, item_name: &Ident, variants: &[(&Variant, Item)]) -> TokenStream {
+pub fn gen_for_enum(item: &Item, item_name: &Ident, variants: &[(&Variant, Item)]) -> TokenStream {
+    if !matches!(&*item.kind(), Kind::Value(_)) {
+        abort! { item.kind().span(),
+            "`{}` cannot be used with `value`",
+            item.kind().name(),
+        }
+    }
+
     let lits = lits(variants);
     let value_variants = gen_value_variants(&lits);
-    let to_possible_value = gen_to_possible_value(&lits);
+    let to_possible_value = gen_to_possible_value(item, &lits);
 
     quote! {
         #[allow(dead_code, unreachable_code, unused_variables, unused_braces)]
@@ -78,12 +85,14 @@ fn lits(variants: &[(&Variant, Item)]) -> Vec<(TokenStream, Ident)> {
                     abort!(variant.span(), "`#[derive(ValueEnum)]` only supports unit variants. Non-unit variants must be skipped");
                 }
                 let fields = item.field_methods(false);
+                let deprecations = item.deprecations();
                 let name = item.cased_name();
                 Some((
-                    quote_spanned! { variant.span()=>
+                    quote_spanned! { variant.span()=> {
+                        #deprecations
                         clap::builder::PossibleValue::new(#name)
                         #fields
-                    },
+                    }},
                     variant.ident.clone(),
                 ))
             }
@@ -101,11 +110,14 @@ fn gen_value_variants(lits: &[(TokenStream, Ident)]) -> TokenStream {
     }
 }
 
-fn gen_to_possible_value(lits: &[(TokenStream, Ident)]) -> TokenStream {
+fn gen_to_possible_value(item: &Item, lits: &[(TokenStream, Ident)]) -> TokenStream {
     let (lit, variant): (Vec<TokenStream>, Vec<Ident>) = lits.iter().cloned().unzip();
 
+    let deprecations = item.deprecations();
+
     quote! {
         fn to_possible_value<'a>(&self) -> ::std::option::Option<clap::builder::PossibleValue> {
+            #deprecations
             match self {
                 #(Self::#variant => Some(#lit),)*
                 _ => None

clap_derive/src/item.rs

@@ -41,6 +41,7 @@ pub struct Item {
     ty: Option<Type>,
     doc_comment: Vec<Method>,
     methods: Vec<Method>,
+    deprecations: Vec<Deprecation>,
     value_parser: Option<ValueParser>,
     action: Option<Action>,
     verbatim_doc_comment: bool,
@@ -57,7 +58,8 @@ impl Item {
         let attrs = &input.attrs;
         let argument_casing = Sp::call_site(DEFAULT_CASING);
         let env_casing = Sp::call_site(DEFAULT_ENV_CASING);
-        Self::from_struct(span, attrs, name, argument_casing, env_casing)
+        let kind = Sp::new(Kind::Command(Sp::new(Ty::Other, span)), span);
+        Self::from_struct(attrs, name, argument_casing, env_casing, kind)
     }
 
     pub fn from_subcommand_enum(input: &DeriveInput, name: Name) -> Self {
@@ -65,7 +67,8 @@ impl Item {
         let attrs = &input.attrs;
         let argument_casing = Sp::call_site(DEFAULT_CASING);
         let env_casing = Sp::call_site(DEFAULT_ENV_CASING);
-        Self::from_struct(span, attrs, name, argument_casing, env_casing)
+        let kind = Sp::new(Kind::Command(Sp::new(Ty::Other, span)), span);
+        Self::from_struct(attrs, name, argument_casing, env_casing, kind)
     }
 
     pub fn from_value_enum(input: &DeriveInput, name: Name) -> Self {
@@ -73,17 +76,18 @@ impl Item {
         let attrs = &input.attrs;
         let argument_casing = Sp::call_site(DEFAULT_CASING);
         let env_casing = Sp::call_site(DEFAULT_ENV_CASING);
-        Self::from_struct(span, attrs, name, argument_casing, env_casing)
+        let kind = Sp::new(Kind::Value(Sp::new(Ty::Other, span)), span);
+        Self::from_struct(attrs, name, argument_casing, env_casing, kind)
     }
 
     fn from_struct(
-        span: Span,
         attrs: &[Attribute],
         name: Name,
         argument_casing: Sp<CasingStyle>,
         env_casing: Sp<CasingStyle>,
+        kind: Sp<Kind>,
     ) -> Self {
-        let mut res = Self::new(span, name, None, argument_casing, env_casing);
+        let mut res = Self::new(name, None, argument_casing, env_casing, kind);
         res.push_attrs(attrs);
         res.push_doc_comment(attrs, "about");
 
@@ -99,17 +103,8 @@ impl Item {
                 "`action` attribute is only allowed on fields"
             );
         }
-        match &*res.kind {
+
-            Kind::Subcommand(_) => abort!(res.kind.span(), "subcommand is only allowed on fields"),
+        res
-            Kind::Skip(_) => abort!(res.kind.span(), "skip is only allowed on fields"),
-            Kind::Arg(_) => res,
-            Kind::FromGlobal(_) => abort!(res.kind.span(), "from_global is only allowed on fields"),
-            Kind::Flatten => abort!(res.kind.span(), "flatten is only allowed on fields"),
-            Kind::ExternalSubcommand => abort!(
-                res.kind.span(),
-                "external_subcommand is only allowed on fields"
-            ),
-        }
     }
 
     pub fn from_subcommand_variant(
@@ -118,13 +113,9 @@ impl Item {
         env_casing: Sp<CasingStyle>,
     ) -> Self {
         let name = variant.ident.clone();
-        let mut res = Self::new(
+        let span = variant.span();
-            variant.span(),
+        let kind = Sp::new(Kind::Command(Sp::new(Ty::Other, span)), span);
-            Name::Derived(name),
+        let mut res = Self::new(Name::Derived(name), None, struct_casing, env_casing, kind);
-            None,
-            struct_casing,
-            env_casing,
-        );
         res.push_attrs(&variant.attrs);
         res.push_doc_comment(&variant.attrs, "about");
 
@@ -153,8 +144,6 @@ impl Item {
                 res.doc_comment = vec![];
             }
 
-            Kind::ExternalSubcommand => (),
-
             Kind::Subcommand(_) => {
                 if let Some(value_parser) = res.value_parser.as_ref() {
                     abort!(
@@ -205,11 +194,13 @@ impl Item {
 
                 res.kind = Sp::new(Kind::Subcommand(ty), res.kind.span());
             }
-            Kind::Skip(_) => (),
+
-            Kind::FromGlobal(_) => {
+            Kind::ExternalSubcommand
-                abort!(res.kind.span(), "from_global is not supported on variants");
+            | Kind::FromGlobal(_)
-            }
+            | Kind::Skip(_)
-            Kind::Arg(_) => (),
+            | Kind::Command(_)
+            | Kind::Value(_)
+            | Kind::Arg(_) => (),
         }
 
         res
@@ -220,12 +211,14 @@ impl Item {
         argument_casing: Sp<CasingStyle>,
         env_casing: Sp<CasingStyle>,
     ) -> Self {
+        let span = variant.span();
+        let kind = Sp::new(Kind::Value(Sp::new(Ty::Other, span)), span);
         let mut res = Self::new(
-            variant.span(),
             Name::Derived(variant.ident.clone()),
             None,
             argument_casing,
             env_casing,
+            kind,
         );
         res.push_attrs(&variant.attrs);
         res.push_doc_comment(&variant.attrs, "help");
@@ -242,17 +235,8 @@ impl Item {
                 "`action` attribute is only allowed on fields"
             );
         }
-        match &*res.kind {
+
-            Kind::Subcommand(_) => abort!(res.kind.span(), "subcommand is only allowed on fields"),
+        res
-            Kind::Skip(_) => res,
-            Kind::Arg(_) => res,
-            Kind::FromGlobal(_) => abort!(res.kind.span(), "from_global is only allowed on fields"),
-            Kind::Flatten => abort!(res.kind.span(), "flatten is only allowed on fields"),
-            Kind::ExternalSubcommand => abort!(
-                res.kind.span(),
-                "external_subcommand is only allowed on fields"
-            ),
-        }
     }
 
     pub fn from_args_field(
@@ -261,12 +245,14 @@ impl Item {
         env_casing: Sp<CasingStyle>,
     ) -> Self {
         let name = field.ident.clone().unwrap();
+        let span = field.span();
+        let kind = Sp::new(Kind::Arg(Sp::new(Ty::Other, span)), span);
         let mut res = Self::new(
-            field.span(),
             Name::Derived(name),
             Some(field.ty.clone()),
             struct_casing,
             env_casing,
+            kind,
         );
         res.push_attrs(&field.attrs);
         res.push_doc_comment(&field.attrs, "help");
@@ -296,12 +282,6 @@ impl Item {
                 res.doc_comment = vec![];
             }
 
-            Kind::ExternalSubcommand => {
-                abort! { res.kind.span(),
-                    "`external_subcommand` can be used only on enum variants"
-                }
-            }
-
             Kind::Subcommand(_) => {
                 if let Some(value_parser) = res.value_parser.as_ref() {
                     abort!(
@@ -390,17 +370,19 @@ impl Item {
                         .unwrap_or_else(|| field.ty.span()),
                 );
             }
+
+            Kind::Command(_) | Kind::Value(_) | Kind::ExternalSubcommand => {}
         }
 
         res
     }
 
     fn new(
-        default_span: Span,
         name: Name,
         ty: Option<Type>,
         casing: Sp<CasingStyle>,
         env_casing: Sp<CasingStyle>,
+        kind: Sp<Kind>,
     ) -> Self {
         Self {
             name,
@@ -409,6 +391,7 @@ impl Item {
             env_casing,
             doc_comment: vec![],
             methods: vec![],
+            deprecations: vec![],
             value_parser: None,
             action: None,
             verbatim_doc_comment: false,
@@ -416,7 +399,7 @@ impl Item {
             next_help_heading: None,
             is_enum: false,
             is_positional: true,
-            kind: Sp::new(Kind::Arg(Sp::new(Ty::Other, default_span)), default_span),
+            kind,
         }
     }
 
@@ -437,7 +420,73 @@ impl Item {
 
     fn push_attrs(&mut self, attrs: &[Attribute]) {
         let parsed = ClapAttr::parse_all(attrs);
+
         for attr in &parsed {
+            if let Some(AttrValue::Call(_)) = &attr.value {
+                continue;
+            }
+
+            let kind = match &attr.magic {
+                Some(MagicAttrName::FromGlobal) => {
+                    if attr.value.is_some() {
+                        let expr = attr.value_or_abort();
+                        abort!(expr, "attribute `{}` does not accept a value", attr.name);
+                    }
+                    let ty = Sp::call_site(Ty::Other);
+                    let kind = Sp::new(Kind::FromGlobal(ty), attr.name.clone().span());
+                    Some(kind)
+                }
+                Some(MagicAttrName::Subcommand) if attr.value.is_none() => {
+                    if attr.value.is_some() {
+                        let expr = attr.value_or_abort();
+                        abort!(expr, "attribute `{}` does not accept a value", attr.name);
+                    }
+                    let ty = Sp::call_site(Ty::Other);
+                    let kind = Sp::new(Kind::Subcommand(ty), attr.name.clone().span());
+                    Some(kind)
+                }
+                Some(MagicAttrName::ExternalSubcommand) if attr.value.is_none() => {
+                    if attr.value.is_some() {
+                        let expr = attr.value_or_abort();
+                        abort!(expr, "attribute `{}` does not accept a value", attr.name);
+                    }
+                    let kind = Sp::new(Kind::ExternalSubcommand, attr.name.clone().span());
+                    Some(kind)
+                }
+                Some(MagicAttrName::Flatten) if attr.value.is_none() => {
+                    if attr.value.is_some() {
+                        let expr = attr.value_or_abort();
+                        abort!(expr, "attribute `{}` does not accept a value", attr.name);
+                    }
+                    let kind = Sp::new(Kind::Flatten, attr.name.clone().span());
+                    Some(kind)
+                }
+                Some(MagicAttrName::Skip) => {
+                    let expr = attr.value.clone();
+                    let kind = Sp::new(Kind::Skip(expr), attr.name.clone().span());
+                    Some(kind)
+                }
+                _ => None,
+            };
+
+            if let Some(kind) = kind {
+                self.set_kind(kind);
+            }
+        }
+
+        for attr in &parsed {
+            match attr.kind.get() {
+                AttrKind::Clap => {}
+                AttrKind::StructOpt => {
+                    self.deprecations.push(Deprecation::attribute(
+                        "4.0.0",
+                        *attr.kind.get(),
+                        AttrKind::Clap,
+                        attr.kind.span(),
+                    ));
+                }
+            }
+
             if let Some(AttrValue::Call(tokens)) = &attr.value {
                 // Force raw mode with method call syntax
                 self.push_method(attr.name.clone(), quote!(#(#tokens),*));
@@ -458,11 +507,23 @@ impl Item {
 
                 #[cfg(not(feature = "unstable-v5"))]
                 Some(MagicAttrName::ValueParser) if attr.value.is_none() => {
+                    self.deprecations.push(Deprecation {
+                        span: attr.name.span(),
+                        id: "bare_value_parser",
+                        version: "4.0.0",
+                        description: "`#[clap(value_parser)]` is now the default and is no longer needed`".to_owned(),
+                    });
                     self.value_parser = Some(ValueParser::Implicit(attr.name.clone()));
                 }
 
                 #[cfg(not(feature = "unstable-v5"))]
                 Some(MagicAttrName::Action) if attr.value.is_none() => {
+                    self.deprecations.push(Deprecation {
+                        span: attr.name.span(),
+                        id: "bare_action",
+                        version: "4.0.0",
+                        description: "`#[clap(action)]` is now the default and is no longer needed`".to_owned(),
+                    });
                     self.action = Some(Action::Implicit(attr.name.clone()));
                 }
 
@@ -473,28 +534,8 @@ impl Item {
                     );
                 }
 
-                Some(MagicAttrName::ValueEnum) if attr.value.is_none() => self.is_enum = true,
+                Some(MagicAttrName::ValueEnum) if attr.value.is_none() => {
-
+                    self.is_enum = true
-                Some(MagicAttrName::FromGlobal) if attr.value.is_none() => {
-                    let ty = Sp::call_site(Ty::Other);
-                    let kind = Sp::new(Kind::FromGlobal(ty), attr.name.clone().span());
-                    self.set_kind(kind);
-                }
-
-                Some(MagicAttrName::Subcommand) if attr.value.is_none() => {
-                    let ty = Sp::call_site(Ty::Other);
-                    let kind = Sp::new(Kind::Subcommand(ty), attr.name.clone().span());
-                    self.set_kind(kind);
-                }
-
-                Some(MagicAttrName::ExternalSubcommand) if attr.value.is_none() => {
-                    let kind = Sp::new(Kind::ExternalSubcommand, attr.name.clone().span());
-                    self.set_kind(kind);
-                }
-
-                Some(MagicAttrName::Flatten) if attr.value.is_none() => {
-                    let kind = Sp::new(Kind::Flatten, attr.name.clone().span());
-                    self.set_kind(kind);
                 }
 
                 Some(MagicAttrName::VerbatimDocComment) if attr.value.is_none() => {
@@ -521,12 +562,6 @@ impl Item {
                     }
                 }
 
-                Some(MagicAttrName::Skip) => {
-                    let expr = attr.value.clone();
-                    let kind = Sp::new(Kind::Skip(expr), attr.name.clone().span());
-                    self.set_kind(kind);
-                }
-
                 Some(MagicAttrName::DefaultValueT) => {
                     let ty = if let Some(ty) = self.ty.as_ref() {
                         ty
@@ -791,14 +826,18 @@ impl Item {
 
                 // Directives that never receive a value
                 Some(MagicAttrName::ValueEnum)
-                | Some(MagicAttrName::FromGlobal)
-                | Some(MagicAttrName::Subcommand)
-                | Some(MagicAttrName::ExternalSubcommand)
-                | Some(MagicAttrName::Flatten)
                 | Some(MagicAttrName::VerbatimDocComment) => {
                     let expr = attr.value_or_abort();
                     abort!(expr, "attribute `{}` does not accept a value", attr.name);
                 }
+
+                // Kinds
+                Some(MagicAttrName::FromGlobal)
+                | Some(MagicAttrName::Subcommand)
+                | Some(MagicAttrName::ExternalSubcommand)
+                | Some(MagicAttrName::Flatten)
+                | Some(MagicAttrName::Skip) => {
+                }
             }
         }
     }
@@ -825,13 +864,24 @@ impl Item {
     }
 
     fn set_kind(&mut self, kind: Sp<Kind>) {
-        if let Kind::Arg(_) = *self.kind {
+        match (self.kind.get(), kind.get()) {
+            (Kind::Arg(_), Kind::FromGlobal(_))
+            | (Kind::Arg(_), Kind::Subcommand(_))
+            | (Kind::Arg(_), Kind::Flatten)
+            | (Kind::Arg(_), Kind::Skip(_))
+            | (Kind::Command(_), Kind::Subcommand(_))
+            | (Kind::Command(_), Kind::Flatten)
+            | (Kind::Command(_), Kind::Skip(_))
+            | (Kind::Command(_), Kind::ExternalSubcommand)
+            | (Kind::Value(_), Kind::Skip(_)) => {
                 self.kind = kind;
-        } else {
+            }
-            abort!(
+
-                kind.span(),
+            (_, _) => {
-                "`subcommand`, `flatten`, `external_subcommand` and `skip` cannot be used together"
+                let old = self.kind.name();
-            );
+                let new = kind.name();
+                abort!(kind.span(), "`{}` cannot be used with `{}`", new, old);
+            }
         }
     }
 
@@ -876,6 +926,11 @@ impl Item {
         }
     }
 
+    pub fn deprecations(&self) -> proc_macro2::TokenStream {
+        let deprecations = &self.deprecations;
+        quote!( #(#deprecations)* )
+    }
+
     pub fn next_display_order(&self) -> TokenStream {
         let next_display_order = self.next_display_order.as_ref().into_iter();
         quote!( #(#next_display_order)* )
@@ -949,11 +1004,11 @@ impl Item {
     }
 
     pub fn casing(&self) -> Sp<CasingStyle> {
-        self.casing.clone()
+        self.casing
     }
 
     pub fn env_casing(&self) -> Sp<CasingStyle> {
-        self.env_casing.clone()
+        self.env_casing
     }
 
     pub fn has_explicit_methods(&self) -> bool {
@@ -1057,6 +1112,8 @@ fn default_action(field_type: &Type, span: Span) -> Method {
 #[derive(Clone)]
 pub enum Kind {
     Arg(Sp<Ty>),
+    Command(Sp<Ty>),
+    Value(Sp<Ty>),
     FromGlobal(Sp<Ty>),
     Subcommand(Sp<Ty>),
     Flatten,
@@ -1064,6 +1121,21 @@ pub enum Kind {
     ExternalSubcommand,
 }
 
+impl Kind {
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Arg(_) => "arg",
+            Self::Command(_) => "command",
+            Self::Value(_) => "value",
+            Self::FromGlobal(_) => "from_global",
+            Self::Subcommand(_) => "subcommand",
+            Self::Flatten => "flatten",
+            Self::Skip(_) => "skip",
+            Self::ExternalSubcommand => "external_subcommand",
+        }
+    }
+}
+
 #[derive(Clone)]
 pub struct Method {
     name: Ident,
@@ -1115,6 +1187,54 @@ impl ToTokens for Method {
     }
 }
 
+#[derive(Clone)]
+pub struct Deprecation {
+    pub span: Span,
+    pub id: &'static str,
+    pub version: &'static str,
+    pub description: String,
+}
+
+impl Deprecation {
+    fn attribute(version: &'static str, old: AttrKind, new: AttrKind, span: Span) -> Self {
+        Self {
+            span,
+            id: "old_attribute",
+            version,
+            description: format!(
+                "Attribute `#[{}(...)]` has been deprecated in favor of `#[{}(...)]`",
+                old.as_str(),
+                new.as_str()
+            ),
+        }
+    }
+}
+
+impl ToTokens for Deprecation {
+    fn to_tokens(&self, ts: &mut proc_macro2::TokenStream) {
+        let tokens = if cfg!(feature = "deprecated") {
+            let Deprecation {
+                span,
+                id,
+                version,
+                description,
+            } = self;
+            let span = *span;
+            let id = Ident::new(id, span);
+
+            quote_spanned!(span=> {
+                #[deprecated(since = #version, note = #description)]
+                fn #id() {}
+                #id();
+            })
+        } else {
+            quote!()
+        };
+
+        tokens.to_tokens(ts);
+    }
+}
+
 /// replace all `:` with `, ` when not inside the `<>`
 ///
 /// `"author1:author2:author3" => "author1, author2, author3"`

clap_derive/src/lib.rs

@@ -42,7 +42,7 @@ pub fn value_enum(input: TokenStream) -> TokenStream {
 /// receiving an instance of `clap::ArgMatches` from conducting parsing, and then
 /// implementing a conversion code to instantiate an instance of the user
 /// context struct.
-#[proc_macro_derive(Parser, attributes(clap))]
+#[proc_macro_derive(Parser, attributes(clap, structopt))]
 #[proc_macro_error]
 pub fn parser(input: TokenStream) -> TokenStream {
     let input: DeriveInput = parse_macro_input!(input);

clap_derive/src/utils/spanned.rs

@@ -5,7 +5,7 @@ use syn::LitStr;
 use std::ops::{Deref, DerefMut};
 
 /// An entity with a span attached.
-#[derive(Debug, Clone)]
+#[derive(Debug, Copy, Clone)]
 pub struct Sp<T> {
     val: T,
     span: Span,
@@ -23,6 +23,10 @@ impl<T> Sp<T> {
         }
     }
 
+    pub fn get(&self) -> &T {
+        &self.val
+    }
+
     pub fn span(&self) -> Span {
         self.span
     }

tests/derive_ui/external_subcommand_misuse.stderr

@@ -1,5 +1,5 @@
-error: `external_subcommand` can be used only on enum variants
+error: `external_subcommand` cannot be used with `arg`
- --> $DIR/external_subcommand_misuse.rs:5:12
+ --> tests/derive_ui/external_subcommand_misuse.rs:5:12
   |
 5 |     #[clap(external_subcommand)]
   |            ^^^^^^^^^^^^^^^^^^^

tests/derive_ui/skip_flatten.stderr

@@ -1,5 +1,5 @@
-error: `subcommand`, `flatten`, `external_subcommand` and `skip` cannot be used together
+error: `flatten` cannot be used with `skip`
-  --> $DIR/skip_flatten.rs:17:18
+  --> tests/derive_ui/skip_flatten.rs:17:18
    |
 17 |     #[clap(skip, flatten)]
    |                  ^^^^^^^

tests/derive_ui/skip_subcommand.stderr

@@ -1,5 +1,5 @@
-error: `subcommand`, `flatten`, `external_subcommand` and `skip` cannot be used together
+error: `skip` cannot be used with `subcommand`
-  --> $DIR/skip_subcommand.rs:17:24
+  --> tests/derive_ui/skip_subcommand.rs:17:24
    |
 17 |     #[clap(subcommand, skip)]
    |                        ^^^^

tests/derive_ui/struct_subcommand.stderr

@@ -1,5 +1,5 @@
-error: subcommand is only allowed on fields
+error: `subcommand` cannot be used with `command`
-  --> $DIR/struct_subcommand.rs:12:24
+  --> tests/derive_ui/struct_subcommand.rs:12:24
    |
 12 | #[clap(name = "basic", subcommand)]
    |                        ^^^^^^^^^^

tests/derive_ui/subcommand_and_flatten.stderr

@@ -1,5 +1,5 @@
-error: `subcommand`, `flatten`, `external_subcommand` and `skip` cannot be used together
+error: `flatten` cannot be used with `subcommand`
-  --> $DIR/subcommand_and_flatten.rs:16:24
+  --> tests/derive_ui/subcommand_and_flatten.rs:16:24
    |
 16 |     #[clap(subcommand, flatten)]
    |                        ^^^^^^^