add cli override for any configuration item

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

Cargo.lock

@@ -708,6 +708,7 @@ dependencies = [
  "tikv-jemallocator",
  "tokio",
  "tokio-metrics",
+ "toml",
  "tracing",
  "tracing-core",
  "tracing-subscriber",

Cargo.toml

@@ -35,6 +35,11 @@ version = "0.2.8"
 version = "0.20"
 features = ["features"]
 
+[workspace.dependencies.toml]
+version = "0.8.14"
+default-features = false
+features = ["parse"]
+
 [workspace.dependencies.sanitize-filename]
 version = "0.5.0"
 

src/core/Cargo.toml

@@ -86,6 +86,7 @@ tikv-jemalloc-sys.optional = true
 tikv-jemalloc-sys.workspace = true
 tokio.workspace = true
 tokio-metrics.workspace = true
+toml.workspace = true
 tracing-core.workspace = true
 tracing-subscriber.workspace = true
 tracing.workspace = true

src/core/config/mod.rs

@@ -9,10 +9,8 @@ use either::{
 	Either,
 	Either::{Left, Right},
 };
-use figment::{
-	providers::{Env, Format, Toml},
-	Figment,
-};
+use figment::providers::{Env, Format, Toml};
+pub use figment::{value::Value as FigmentValue, Figment};
 use itertools::Itertools;
 use regex::RegexSet;
 use ruma::{
@@ -408,8 +406,8 @@ const DEPRECATED_KEYS: &[&str; 9] = &[
 ];
 
 impl Config {
-	/// Initialize config
-	pub fn new(path: &Option<PathBuf>) -> Result<Self> {
+	/// Pre-initialize config
+	pub fn load(path: &Option<PathBuf>) -> Result<Figment> {
 		let raw_config = if let Some(config_file_env) = Env::var("CONDUIT_CONFIG") {
 			Figment::new()
 				.merge(Toml::file(config_file_env).nested())
@@ -431,13 +429,18 @@ impl Config {
 				.merge(Env::prefixed("CONDUWUIT_").global().split("__"))
 		};
 
+		Ok(raw_config)
+	}
+
+	/// Finalize config
+	pub fn new(raw_config: &Figment) -> Result<Self> {
 		let config = match raw_config.extract::<Self>() {
 			Err(e) => return Err!("There was a problem with your configuration file: {e}"),
 			Ok(config) => config,
 		};
 
 		// don't start if we're listening on both UNIX sockets and TCP at same time
-		check::is_dual_listening(&raw_config)?;
+		check::is_dual_listening(raw_config)?;
 
 		Ok(config)
 	}

src/core/error/mod.rs

@@ -57,6 +57,12 @@ pub enum Error {
 	HttpHeader(#[from] http::header::InvalidHeaderValue),
 	#[error("{0}")]
 	CargoToml(#[from] cargo_toml::Error),
+	#[error("{0}")]
+	FigmentError(#[from] figment::error::Error),
+	#[error("{0}")]
+	TomlSerError(#[from] toml::ser::Error),
+	#[error("{0}")]
+	TomlDeError(#[from] toml::de::Error),
 
 	// ruma
 	#[error("{0}")]

src/core/mod.rs

@@ -10,6 +10,7 @@ pub mod pdu;
 pub mod server;
 pub mod utils;
 
+pub use ::toml;
 pub use config::Config;
 pub use error::Error;
 pub use info::{rustc_flags_capture, version, version::version};

src/main/clap.rs

@@ -3,16 +3,24 @@
 use std::path::PathBuf;
 
 use clap::Parser;
-use conduit::{Config, Result};
+use conduit::{
+	config::{Figment, FigmentValue},
+	err, toml, Err, Result,
+};
 
 /// Commandline arguments
 #[derive(Parser, Debug)]
 #[clap(version = conduit::version(), about, long_about = None)]
 pub(crate) struct Args {
 	#[arg(short, long)]
-	/// Optional argument to the path of a conduwuit config TOML file
+	/// Path to the config TOML file (optional)
 	pub(crate) config: Option<PathBuf>,
 
+	/// Override a configuration variable using TOML 'key=value' syntax
+	#[arg(long, short('O'))]
+	pub(crate) option: Vec<String>,
+
+	#[cfg(feature = "console")]
 	/// Activate admin command console automatically after startup.
 	#[arg(long, num_args(0))]
 	pub(crate) console: bool,
@@ -23,10 +31,38 @@ pub(crate) struct Args {
 pub(super) fn parse() -> Args { Args::parse() }
 
 /// Synthesize any command line options with configuration file options.
-pub(crate) fn update(config: &mut Config, args: &Args) -> Result<()> {
+pub(crate) fn update(mut config: Figment, args: &Args) -> Result<Figment> {
+	#[cfg(feature = "console")]
 	// Indicate the admin console should be spawned automatically if the
 	// configuration file hasn't already.
-	config.admin_console_automatic |= args.console;
+	if args.console {
+		config = config.join(("admin_console_automatic", true));
+	}
 
-	Ok(())
+	// All other individual overrides can go last in case we have options which
+	// set multiple conf items at once and the user still needs granular overrides.
+	for option in &args.option {
+		let (key, val) = option
+			.split_once('=')
+			.ok_or_else(|| err!("Missing '=' in -O/--option: {option:?}"))?;
+
+		if key.is_empty() {
+			return Err!("Missing key= in -O/--option: {option:?}");
+		}
+
+		if val.is_empty() {
+			return Err!("Missing =val in -O/--option: {option:?}");
+		}
+
+		// The value has to pass for what would appear as a line in the TOML file.
+		let val = toml::from_str::<FigmentValue>(option)?;
+		let FigmentValue::Dict(_, val) = val else {
+			panic!("Unexpected Figment Value: {val:#?}");
+		};
+
+		// Figment::merge() overrides existing
+		config = config.merge((key, val[key].clone()));
+	}
+
+	Ok(config)
 }

src/main/server.rs

@@ -22,8 +22,9 @@ pub(crate) struct Server {
 
 impl Server {
 	pub(crate) fn build(args: &Args, runtime: Option<&runtime::Handle>) -> Result<Arc<Self>, Error> {
-		let mut config = Config::new(&args.config)?;
-		crate::clap::update(&mut config, args)?;
+		let raw_config = Config::load(&args.config)?;
+		let raw_config = crate::clap::update(raw_config, args)?;
+		let config = Config::new(&raw_config)?;
 
 		#[cfg(feature = "sentry_telemetry")]
 		let sentry_guard = crate::sentry::init(&config);