add cargo manifest reflection

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/Cargo.toml

@@ -53,8 +53,10 @@ sha256_media = []
 argon2.workspace = true
 axum.workspace = true
 bytes.workspace = true
+cargo_toml.workspace = true
 checked_ops.workspace = true
 chrono.workspace = true
+conduit-macros.workspace = true
 const-str.workspace = true
 either.workspace = true
 figment.workspace = true

src/core/error/mod.rs

@@ -55,6 +55,8 @@ pub enum Error {
 	Http(#[from] http::Error),
 	#[error("{0}")]
 	HttpHeader(#[from] http::header::InvalidHeaderValue),
+	#[error("{0}")]
+	CargoToml(#[from] cargo_toml::Error),
 
 	// ruma
 	#[error("{0}")]

src/core/info/cargo.rs

@@ -0,0 +1,66 @@
+//! Information about the build related to Cargo. This is a frontend interface
+//! informed by proc-macros that capture raw information at build time which is
+//! further processed at runtime either during static initialization or as
+//! necessary.
+
+use std::sync::OnceLock;
+
+use cargo_toml::Manifest;
+use conduit_macros::cargo_manifest;
+
+use crate::Result;
+
+// Raw captures of the cargo manifest for each crate. This is provided by a
+// proc-macro at build time since the source directory and the cargo toml's may
+// not be present during execution.
+
+#[cargo_manifest]
+const WORKSPACE_MANIFEST: &'static str = ();
+#[cargo_manifest("macros")]
+const MACROS_MANIFEST: &'static str = ();
+#[cargo_manifest("core")]
+const CORE_MANIFEST: &'static str = ();
+#[cargo_manifest("database")]
+const DATABASE_MANIFEST: &'static str = ();
+#[cargo_manifest("service")]
+const SERVICE_MANIFEST: &'static str = ();
+#[cargo_manifest("admin")]
+const ADMIN_MANIFEST: &'static str = ();
+#[cargo_manifest("router")]
+const ROUTER_MANIFEST: &'static str = ();
+#[cargo_manifest("main")]
+const MAIN_MANIFEST: &'static str = ();
+
+/// Processed list of features access all project crates. This is generated from
+/// the data in the MANIFEST strings and contains all possible project features.
+/// For *enabled* features see the info::rustc module instead.
+static FEATURES: OnceLock<Vec<String>> = OnceLock::new();
+
+/// List of all possible features for the project. For *enabled* features in
+/// this build see the companion function in info::rustc.
+pub fn features() -> &'static Vec<String> {
+	FEATURES.get_or_init(|| init_features().unwrap_or_else(|e| panic!("Failed initialize features: {e}")))
+}
+
+fn init_features() -> Result<Vec<String>> {
+	let mut features = Vec::new();
+	append_features(&mut features, WORKSPACE_MANIFEST)?;
+	append_features(&mut features, MACROS_MANIFEST)?;
+	append_features(&mut features, CORE_MANIFEST)?;
+	append_features(&mut features, DATABASE_MANIFEST)?;
+	append_features(&mut features, SERVICE_MANIFEST)?;
+	append_features(&mut features, ADMIN_MANIFEST)?;
+	append_features(&mut features, ROUTER_MANIFEST)?;
+	append_features(&mut features, MAIN_MANIFEST)?;
+	features.sort();
+	features.dedup();
+
+	Ok(features)
+}
+
+fn append_features(features: &mut Vec<String>, manifest: &str) -> Result<()> {
+	let manifest = Manifest::from_str(manifest)?;
+	features.extend(manifest.features.keys().cloned());
+
+	Ok(())
+}

src/core/info/mod.rs

@@ -1,4 +1,5 @@
 //! Information about the project. This module contains version, build, system,
 //! etc information which can be queried by admins or used by developers.
 
+pub mod cargo;
 pub mod version;