Make error message smaller

I've noticed that the long, noisy error messages often get in the way of conversations,
and also that users don't realize they can edit or delete their message to make it go away.
This addresses both of those issues.

bot/Cargo.toml

@@ -18,3 +18,4 @@ serenity = { version = "0.12", default_features = false, features = [
 rusqlite = { version = "0.29", features = ["bundled"] }
 thiserror = "1"
 tokio = { version = "1", features = ["rt", "macros", "sync"] }
+tracing = "0.1"

bot/src/bot.rs

@@ -640,6 +640,28 @@ async fn list_tags(
 	Ok(())
 }
 
+async fn handle_error(
+	error: poise::FrameworkError<'_, Data, Box<dyn std::error::Error + Send + Sync>>,
+) -> serenity::Result<()> {
+	if let poise::FrameworkError::ArgumentParse {
+		ctx, input, error, ..
+	} = error
+	{
+		let name = &ctx.command().name;
+		let usage = format!(
+			"Use `?help {name}` for usage. Feel free to edit or delete your message and the bot will react.",
+		);
+		let response = input.map_or_else(
+			|| format!("**{error}**\n{usage}"),
+			|input| format!("**Cannot parse `{input}` as argument: {error}**\n{usage}"),
+		);
+		ctx.reply(response).await?;
+		Ok(())
+	} else {
+		poise::builtins::on_error(error).await
+	}
+}
+
 pub async fn run() {
 	let database = Connection::open_with_flags(
 		std::env::var_os("DB_PATH").expect("need `DB_PATH` env var"),
@@ -674,6 +696,13 @@ pub async fn run() {
 				list_tags(),
 			],
 			allowed_mentions: Some(CreateAllowedMentions::new()),
+			on_error: |error| {
+				Box::pin(async move {
+					if let Err(error) = handle_error(error).await {
+						tracing::error!(?error, "Error while handling error");
+					}
+				})
+			},
 			..Default::default()
 		})
 		.setup(|ctx, _ready, framework| {