sp-debug-derive: Add force-debug feature (#9996)

* sp-debug-derive: Add `force-debug` feature

Sometimes users want to have proper debug information even inside the
wasm runtime, when they use `RuntimeDebug`. To not fork Substrate to
change a type to a normal `Debug` derive, this pr introduces the
`force-debug` feature. This feature can be enabled by the user in their
runtime and then the types will use the normal Debug derive instead of
printing `wasm:stripped`.

* Fixes

substrate/primitives/debug-derive/Cargo.toml

@@ -22,6 +22,12 @@ syn = "1.0.80"
 proc-macro2 = "1.0"
 
 [features]
+default = [ "std" ]
 std = []
+# By default `RuntimeDebug` implements `Debug` that outputs `<wasm:stripped>` when `std` is
+# disabled. However, sometimes downstream users need to have the real `Debug` implementation for
+# debugging purposes. If this is required, a user only needs to add this crate as a dependency of
+# their runtime and enable the `force-debug` feature.
+force-debug = []
 
 [dev-dependencies]

substrate/primitives/debug-derive/src/impls.rs

@@ -43,7 +43,7 @@ pub fn debug_derive(ast: DeriveInput) -> proc_macro::TokenStream {
 	gen.into()
 }
 
-#[cfg(not(feature = "std"))]
+#[cfg(all(not(feature = "std"), not(feature = "force-debug")))]
 mod implementation {
 	use super::*;
 
@@ -58,7 +58,7 @@ mod implementation {
 	}
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "force-debug"))]
 mod implementation {
 	use super::*;
 	use proc_macro2::Span;