externally visible test macro

Author: devrandom

Cargo.toml

@@ -15,6 +15,7 @@ members = [
     "lightning-custom-message",
     "lightning-transaction-sync",
     "possiblyrandom",
+    "ext-test-macro",
 ]
 
 exclude = [

ext-test-macro/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "ext-test-macro"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+syn = { version = "1.0", features = ["full"] }
+quote = "1.0"
+proc-macro2 = "1.0"

ext-test-macro/src/lib.rs

@@ -0,0 +1,80 @@
+use proc_macro::TokenStream;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::quote;
+use syn::{parse_macro_input, Item};
+
+/// An exposed test.  This is a test that will run locally and also be
+/// made available to other crates that want to run it in their own context.
+///
+/// For example:
+/// ```rust
+/// use ext_test_macro::xtest;
+///
+/// fn f1() {}
+///
+/// #[xtest(feature = "_test_utils")]
+/// pub fn test_f1() {
+///     f1();
+/// }
+/// ```
+///
+/// May also be applied to modules, like so:
+///
+/// ```rust
+/// use ext_test_macro::xtest;
+///
+/// #[xtest(feature = "_test_utils")]
+/// pub mod tests {
+/// 	use super::*;
+///
+///     fn f1() {}
+///
+/// 	#[xtest]
+/// 	pub fn test_f1() {
+/// 	    f1();
+/// 	}
+/// }
+/// ```
+///
+/// Which will include the module if we are testing or the `_test_utils` feature
+/// is on.
+#[proc_macro_attribute]
+pub fn xtest(attrs: TokenStream, item: TokenStream) -> TokenStream {
+	let attrs = parse_macro_input!(attrs as TokenStream2);
+	let input = parse_macro_input!(item as Item);
+
+	let expanded = match input {
+		Item::Mod(item_mod) => {
+			let cfg = if attrs.is_empty() {
+				quote! { #[cfg(test)] }
+			} else {
+				quote! { #[cfg(any(test, #attrs))] }
+			};
+			quote! {
+				#cfg
+				#item_mod
+			}
+		},
+		Item::Fn(item_fn) => {
+			let cfg_attr = if attrs.is_empty() {
+				quote! { #[cfg(test)] }
+			} else {
+				quote! { #[cfg(any(test, #attrs))] }
+			};
+			quote! {
+				#cfg_attr
+				#item_fn
+			}
+		},
+		_ => {
+			return syn::Error::new_spanned(
+				input,
+				"xtest can only be applied to functions or modules",
+			)
+			.to_compile_error()
+			.into();
+		},
+	};
+
+	TokenStream::from(expanded)
+}

lightning/Cargo.toml

@@ -53,6 +53,7 @@ libm = { version = "0.2", default-features = false }
 [dev-dependencies]
 regex = "1.5.6"
 lightning-types = { version = "0.1.0", path = "../lightning-types", features = ["_test_utils"] }
+ext-test-macro = { path = "../ext-test-macro" }
 
 [dev-dependencies.bitcoin]
 version = "0.32.2"