feat: Add ability to inspect build information and features at runtime

Also re-adds ability to inspect used features

src/macros/Cargo.toml

@@ -2,6 +2,7 @@
 name = "conduwuit_macros"
 description.workspace = true
 edition.workspace = true
+homepage.workspace = true
 license.workspace = true
 readme.workspace = true
 repository.workspace = true
@@ -17,6 +18,7 @@ syn.workspace = true
 quote.workspace = true
 proc-macro2.workspace = true
 itertools.workspace = true
+cargo_toml.workspace = true
 
 [lints]
 workspace = true

src/macros/build_info.rs

@@ -0,0 +1,63 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+
+use crate::Result;
+
+pub(super) fn introspect(_args: TokenStream) -> Result<TokenStream> {
+	let cargo_crate_name = std::env::var("CARGO_CRATE_NAME").unwrap();
+	let crate_name = cargo_crate_name.trim_start_matches("conduwuit_");
+	let is_core = cargo_crate_name == "conduwuit_core";
+
+	let flags = std::env::args().collect::<Vec<_>>();
+
+	let mut enabled_features = Vec::new();
+	append_features(&mut enabled_features, flags);
+
+	let enabled_count = enabled_features.len();
+
+	let import_path = if is_core {
+		quote! { use crate::conduwuit_core; }
+	} else {
+		quote! { use ::conduwuit_core; }
+	};
+
+	let ret = quote! {
+		#[doc(hidden)]
+		mod __compile_introspection {
+			#import_path
+
+			/// Features that were enabled when this crate was compiled
+			const ENABLED: [&str; #enabled_count] = [#( #enabled_features ),*];
+
+			const CRATE_NAME: &str = #crate_name;
+
+			/// Register this crate's features with the global registry during static initialization
+			#[::ctor::ctor]
+			fn register() {
+				conduwuit_core::info::introspection::ENABLED_FEATURES.lock().unwrap().insert(#crate_name, &ENABLED);
+			}
+			#[::ctor::dtor]
+			fn unregister() {
+				conduwuit_core::info::introspection::ENABLED_FEATURES.lock().unwrap().remove(#crate_name);
+			}
+		}
+	};
+
+	Ok(ret)
+}
+
+fn append_features(features: &mut Vec<String>, flags: Vec<String>) {
+	let mut next_is_cfg = false;
+	for flag in flags {
+		let is_cfg = flag == "--cfg";
+		let is_feature = flag.starts_with("feature=");
+		if std::mem::replace(&mut next_is_cfg, is_cfg) && is_feature {
+			if let Some(feature) = flag
+				.split_once('=')
+				.map(|(_, feature)| feature.trim_matches('"'))
+			{
+				features.push(feature.to_owned());
+			}
+		}
+	}
+}

src/macros/mod.rs

@@ -1,4 +1,5 @@
 mod admin;
+mod build_info;
 mod config;
 mod debug;
 mod implement;
@@ -44,6 +45,13 @@ pub fn config_example_generator(args: TokenStream, input: TokenStream) -> TokenS
 	attribute_macro::<ItemStruct, _>(args, input, config::example_generator)
 }
 
+#[proc_macro]
+pub fn introspect_crate(input: TokenStream) -> TokenStream {
+	build_info::introspect(input.into())
+		.unwrap_or_else(|e| e.to_compile_error())
+		.into()
+}
+
 fn attribute_macro<I, F>(args: TokenStream, input: TokenStream, func: F) -> TokenStream
 where
 	F: Fn(I, &[Meta]) -> Result<TokenStream>,