Introduce dedicated ParseResult to simplify error handling in main

swap/src/bin/swap.rs

@@ -20,10 +20,8 @@ use std::future::Future;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
-use structopt::clap;
-use structopt::clap::ErrorKind;
 use swap::bitcoin::TxLock;
-use swap::cli::command::{parse_args_and_apply_defaults, Arguments, Command};
+use swap::cli::command::{parse_args_and_apply_defaults, Arguments, Command, ParseResult};
 use swap::database::Database;
 use swap::env::Config;
 use swap::network::quote::BidQuote;
@@ -47,22 +45,12 @@ async fn main() -> Result<()> {
         debug,
         json,
         cmd,
-    } = match parse_args_and_apply_defaults(env::args_os()) {
+    } = match parse_args_and_apply_defaults(env::args_os())? {
-        Ok(args) => args,
+        ParseResult::Arguments(args) => args,
-        Err(e) => {
+        ParseResult::PrintAndExitZero { message } => {
-            if let Some(clap_err) = e.downcast_ref::<clap::Error>() {
+            println!("{}", message);
-                match clap_err.kind {
-                    ErrorKind::HelpDisplayed | ErrorKind::VersionDisplayed => {
-                        println!("{}", clap_err.message);
             std::process::exit(0);
         }
-                    _ => {
-                        bail!(e);
-                    }
-                }
-            }
-            bail!(e);
-        }
     };
 
     match cmd {

swap/src/cli/command.rs

@@ -7,7 +7,7 @@ use libp2p::PeerId;
 use std::ffi::OsString;
 use std::path::PathBuf;
 use std::str::FromStr;
-use structopt::StructOpt;
+use structopt::{clap, StructOpt};
 use url::Url;
 use uuid::Uuid;
 
@@ -34,13 +34,37 @@ pub struct Arguments {
     pub cmd: Command,
 }
 
-pub fn parse_args_and_apply_defaults<I, T>(raw_args: I) -> Result<Arguments>
+/// Represents the result of parsing the command-line parameters.
+#[derive(Debug, PartialEq)]
+pub enum ParseResult {
+    /// The arguments we were invoked in.
+    Arguments(Arguments),
+    /// A flag or command was given that does not need further processing other
+    /// than printing the provided message.
+    ///
+    /// The caller should exit the program with exit code 0.
+    PrintAndExitZero { message: String },
+}
+
+pub fn parse_args_and_apply_defaults<I, T>(raw_args: I) -> Result<ParseResult>
 where
     I: IntoIterator<Item = T>,
     T: Into<OsString> + Clone,
 {
-    let matches = RawArguments::clap().get_matches_from_safe(raw_args)?;
+    let args = match RawArguments::clap().get_matches_from_safe(raw_args) {
-    let args = RawArguments::from_clap(&matches);
+        Ok(matches) => RawArguments::from_clap(&matches),
+        Err(clap::Error {
+            message,
+            kind: clap::ErrorKind::HelpDisplayed,
+            ..
+        })
+        | Err(clap::Error {
+            message,
+            kind: clap::ErrorKind::VersionDisplayed,
+            ..
+        }) => return Ok(ParseResult::PrintAndExitZero { message }),
+        Err(e) => anyhow::bail!(e),
+    };
 
     let debug = args.debug;
     let json = args.json;
@@ -176,7 +200,7 @@ where
         },
     };
 
-    Ok(arguments)
+    Ok(ParseResult::Arguments(arguments))
 }
 
 #[derive(Debug, PartialEq)]
@@ -490,8 +514,9 @@ mod tests {
             PEER_ID,
         ];
 
-        let expected_args = Arguments::buy_xmr_mainnet_defaults();
+        let expected_args = ParseResult::Arguments(Arguments::buy_xmr_mainnet_defaults());
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
+
         assert_eq!(expected_args, args);
     }
 
@@ -510,7 +535,11 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::buy_xmr_testnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::buy_xmr_testnet_defaults())
+        );
     }
 
     #[test]
@@ -576,7 +605,11 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_mainnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_mainnet_defaults())
+        );
     }
 
     #[test]
@@ -594,7 +627,11 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_testnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_testnet_defaults())
+        );
     }
 
     #[test]
@@ -602,7 +639,11 @@ mod tests {
         let raw_ars = vec![BINARY_NAME, "cancel", "--swap-id", SWAP_ID];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::cancel_mainnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::cancel_mainnet_defaults())
+        );
     }
 
     #[test]
@@ -610,7 +651,11 @@ mod tests {
         let raw_ars = vec![BINARY_NAME, "--testnet", "cancel", "--swap-id", SWAP_ID];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::cancel_testnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::cancel_testnet_defaults())
+        );
     }
 
     #[test]
@@ -618,7 +663,11 @@ mod tests {
         let raw_ars = vec![BINARY_NAME, "refund", "--swap-id", SWAP_ID];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::refund_mainnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::refund_mainnet_defaults())
+        );
     }
 
     #[test]
@@ -626,7 +675,11 @@ mod tests {
         let raw_ars = vec![BINARY_NAME, "--testnet", "refund", "--swap-id", SWAP_ID];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::refund_testnet_defaults());
+
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::refund_testnet_defaults())
+        );
     }
 
     #[test]
@@ -647,10 +700,13 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
+
         assert_eq!(
             args,
+            ParseResult::Arguments(
                 Arguments::buy_xmr_mainnet_defaults()
                     .with_data_dir(PathBuf::from_str(data_dir).unwrap())
+            )
         );
 
         let raw_ars = vec![
@@ -668,10 +724,13 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
+
         assert_eq!(
             args,
+            ParseResult::Arguments(
                 Arguments::buy_xmr_testnet_defaults()
                     .with_data_dir(PathBuf::from_str(data_dir).unwrap())
+            )
         );
 
         let raw_ars = vec![
@@ -688,10 +747,13 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
+
         assert_eq!(
             args,
+            ParseResult::Arguments(
                 Arguments::resume_mainnet_defaults()
                     .with_data_dir(PathBuf::from_str(data_dir).unwrap())
+            )
         );
 
         let raw_ars = vec![
@@ -709,10 +771,13 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
+
         assert_eq!(
             args,
+            ParseResult::Arguments(
                 Arguments::resume_testnet_defaults()
                     .with_data_dir(PathBuf::from_str(data_dir).unwrap())
+            )
         );
     }
 
@@ -731,7 +796,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::buy_xmr_mainnet_defaults().with_debug());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::buy_xmr_mainnet_defaults().with_debug())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -747,7 +815,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::buy_xmr_testnet_defaults().with_debug());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::buy_xmr_testnet_defaults().with_debug())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -762,7 +833,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_mainnet_defaults().with_debug());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_mainnet_defaults().with_debug())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -778,7 +852,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_testnet_defaults().with_debug());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_testnet_defaults().with_debug())
+        );
     }
 
     #[test]
@@ -796,7 +873,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::buy_xmr_mainnet_defaults().with_json());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::buy_xmr_mainnet_defaults().with_json())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -812,7 +892,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::buy_xmr_testnet_defaults().with_json());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::buy_xmr_testnet_defaults().with_json())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -827,7 +910,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_mainnet_defaults().with_json());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_mainnet_defaults().with_json())
+        );
 
         let raw_ars = vec![
             BINARY_NAME,
@@ -843,7 +929,10 @@ mod tests {
         ];
 
         let args = parse_args_and_apply_defaults(raw_ars).unwrap();
-        assert_eq!(args, Arguments::resume_testnet_defaults().with_json());
+        assert_eq!(
+            args,
+            ParseResult::Arguments(Arguments::resume_testnet_defaults().with_json())
+        );
     }
 
     impl Arguments {