From 5881bd02cae000164a4df42be099811de44a28b7 Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Tue, 14 Jun 2022 14:29:26 -0500
Subject: [PATCH] fix(derive): Provide derive-friendly deprecation messages

This is a step towards #3822.  I'd say this fixes it but I'd want some
user acceptance before doing so.
---
 clap_derive/src/attrs.rs        |  4 +++
 clap_derive/src/derives/args.rs | 43 +++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/clap_derive/src/attrs.rs b/clap_derive/src/attrs.rs
index 39f1735557a..fb35d31f2d1 100644
--- a/clap_derive/src/attrs.rs
+++ b/clap_derive/src/attrs.rs
@@ -825,6 +825,10 @@ impl Attrs {
         self.value_parser.is_some() || self.action.is_some()
     }
 
+    pub fn explicit_parser(&self) -> bool {
+        self.parser.is_some()
+    }
+
     pub fn parser(&self, field_type: &Type) -> Sp<Parser> {
         self.parser
             .clone()
diff --git a/clap_derive/src/derives/args.rs b/clap_derive/src/derives/args.rs
index 23a2260e644..4195a081082 100644
--- a/clap_derive/src/derives/args.rs
+++ b/clap_derive/src/derives/args.rs
@@ -275,6 +275,45 @@ pub fn gen_augment(
                         quote!()
                     }
                 };
+                let parse_deprecation = match *parser.kind {
+                    _ if !attrs.explicit_parser() || cfg!(not(feature = "deprecated")) => quote!(),
+                    ParserKind::FromStr => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(value_parser = ...)]`")]
+                        fn parse_from_str() {
+                        }
+                        parse_from_str();
+                    },
+                    ParserKind::TryFromStr => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(value_parser = ...)]`")]
+                        fn parse_try_from_str() {
+                        }
+                        parse_try_from_str();
+                    },
+                    ParserKind::FromOsStr => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(value_parser)]` for `PathBuf` or `#[clap(value_parser = ...)]` with a custom `TypedValueParser`")]
+                        fn parse_from_os_str() {
+                        }
+                        parse_from_os_str();
+                    },
+                    ParserKind::TryFromOsStr => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(value_parser = ...)]` with a custom `TypedValueParser`")]
+                        fn parse_try_from_os_str() {
+                        }
+                        parse_try_from_os_str();
+                    },
+                    ParserKind::FromFlag => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(action = ArgAction::SetTrue)]`")]
+                        fn parse_from_flag() {
+                        }
+                        parse_from_flag();
+                    },
+                    ParserKind::FromOccurrences => quote_spanned! { func.span()=>
+                        #[deprecated(since = "3.2.0", note = "Replaced with `#[clap(action = ArgAction::Count)]` with a field type of `u8`")]
+                        fn parse_from_occurrences() {
+                        }
+                        parse_from_occurrences();
+                    },
+                };
 
                 let value_name = attrs.value_name();
                 let possible_values = if attrs.is_enum() && !attrs.ignore_parser() {
@@ -408,8 +447,12 @@ pub fn gen_augment(
 
                 Some(quote_spanned! { field.span()=>
                     let #app_var = #app_var.arg({
+                        #parse_deprecation
+
+                        #[allow(deprecated)]
                         let arg = clap::Arg::new(#id)
                             #implicit_methods;
+
                         let arg = arg
                             #explicit_methods;
                         arg