Merge clap-rs#2092

2092: Make caching in crate_authors! actually work r=pksunkara a=CreepySkeleton



Co-authored-by: CreepySkeleton <creepy-skeleton@yandex.ru>

Cargo.toml

@@ -93,7 +93,7 @@ color       = ["atty", "termcolor"]
 wrap_help   = ["terminal_size", "textwrap/terminal_size"]
 derive      = ["clap_derive", "lazy_static"]
 yaml        = ["yaml-rust"]
-cargo       = [] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
+cargo       = ["lazy_static"] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
 unstable    = ["clap_derive/unstable"] # for building with unstable clap features (doesn't require nightly Rust) (currently none)
 debug       = ["clap_derive/debug"] # Enables debug messages
 doc         = ["yaml"] # All the features which add to documentation

src/lib.rs

@@ -39,8 +39,8 @@ pub use yaml_rust::YamlLoader;
 #[cfg_attr(feature = "derive", doc(hidden))]
 pub use clap_derive::{self, *};
 
-#[cfg(feature = "derive")]
-#[cfg_attr(feature = "derive", doc(hidden))]
+#[cfg(any(feature = "derive", feature = "cargo"))]
+#[doc(hidden)]
 pub use lazy_static;
 
 #[macro_use]

src/macros.rs

@@ -80,42 +80,12 @@ macro_rules! crate_version {
 #[macro_export]
 macro_rules! crate_authors {
     ($sep:expr) => {{
-        use std::ops::Deref;
-        use std::boxed::Box;
-        use std::cell::Cell;
-
-        #[allow(missing_copy_implementations)]
-        #[allow(unused)]
-        struct CargoAuthors {
-            authors: Cell<Option<&'static str>>,
-            __private_field: (),
-        };
-
-        impl Deref for CargoAuthors {
-            type Target = str;
-
-            fn deref(&self) -> &'static str {
-                let authors = self.authors.take();
-                if authors.is_some() {
-                    let unwrapped_authors = authors.unwrap();
-                    self.authors.replace(Some(unwrapped_authors));
-                    unwrapped_authors
-                } else {
-                    // This caches the result for subsequent invocations of the same instance of the macro
-                    // to avoid performing one memory allocation per call.
-                    // If performance ever becomes a problem for this code, it should be moved to build.rs
-                    let s: Box<String> = Box::new(env!("CARGO_PKG_AUTHORS").replace(':', $sep));
-                    let static_string = Box::leak(s);
-                    self.authors.replace(Some(&*static_string));
-                    &*static_string // weird but compiler-suggested way to turn a String into &str
-                }
-            }
+        clap::lazy_static::lazy_static! {
+            static ref CACHED: String = env!("CARGO_PKG_AUTHORS").replace(':', $sep);
         }
 
-        &*CargoAuthors {
-            authors: std::cell::Cell::new(Option::None),
-            __private_field: (),
-        }
+        let s: &'static str = &*CACHED;
+        s
     }};
     () => {
         env!("CARGO_PKG_AUTHORS")