Return Result from CSP parse_reader, better error messages

Cargo.lock

@@ -28,6 +28,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61604a8f862e1d5c3229fdd78f8b02c68dcf73a4c4b05fd636d12240aaa242c1"
+
 [[package]]
 name = "arrayref"
 version = "0.3.6"
@@ -711,6 +717,7 @@ checksum = "624a8340c38c1b80fd549087862da4ba43e08858af025b236e509b6649fc13d5"
 name = "opentally"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "assert_cmd",
  "clap",
  "console_error_panic_hook",

Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 crate-type = ["lib", "cdylib"]
 
 [dependencies]
+anyhow = "1.0.44"
 csv = "1.1.6"
 derive_builder = "0.10.2"
 derive_more = "0.99.14"

src/cli/convert.rs

@@ -113,7 +113,7 @@ pub fn main(mut cmd_opts: SubcmdOptions) -> Result<(), i32> {
 		}
 		"csp" => {
 			let file = File::open(cmd_opts.infile).expect("IO Error");
-			election = parser::csp::parse_reader(file, cmd_opts.require_1, cmd_opts.require_sequential, cmd_opts.require_strict_order);
+			election = parser::csp::parse_reader(file, cmd_opts.require_1, cmd_opts.require_sequential, cmd_opts.require_strict_order).expect("Syntax Error");
 		}
 		_ => unreachable!()
 	};

src/parser/csp.rs

@@ -18,6 +18,7 @@
 use crate::election::{Ballot, Candidate, Election};
 use crate::numbers::Number;
 
+use anyhow::{Context, Result};
 use csv::ReaderBuilder;
 use itertools::Itertools;
 
@@ -25,7 +26,7 @@ use std::collections::HashMap;
 use std::io::Read;
 
 /// Parse the given CSP file
-pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequential: bool, require_strict_order: bool) -> Election<N> {
+pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequential: bool, require_strict_order: bool) -> Result<Election<N>> {
 	// Read CSV file
 	let mut reader = ReaderBuilder::new()
 		.has_headers(true)
@@ -33,14 +34,14 @@ pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequ
 	
 	// Read candidates
 	let mut candidates = Vec::new();
-	let mut idx_map = HashMap::new(); // Map csp index -> candidates index
+	let mut col_map = HashMap::new(); // Map csp column -> candidates index
 	
-	for (i, cand_name) in reader.headers().expect("Syntax Error").into_iter().enumerate() {
+	for (i, cand_name) in reader.headers()?.into_iter().enumerate() {
 		if cand_name == "$mult" {
 			continue;
 		}
 		
-		idx_map.insert(i, candidates.len());
+		col_map.insert(i, candidates.len());
 		candidates.push(Candidate {
 			name: cand_name.to_string(),
 		});
@@ -49,22 +50,22 @@ pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequ
 	// Read ballots
 	let mut ballots = Vec::new();
 	
-	for record in reader.into_records() {
+	for (csv_row, record) in reader.into_records().enumerate() {
-		let record = record.expect("Syntax Error");
+		let record = record?;
 		
 		let mut value = N::one();
 		
 		// Record preferences
 		let mut preferences = Vec::new(); // Vec of (ranking, candidate index)
-		for (csv_index, preference) in record.into_iter().enumerate() {
+		for (csv_col, preference) in record.into_iter().enumerate() {
-			match idx_map.get(&csv_index) {
+			match col_map.get(&csv_col) {
 				Some(cand_index) => {
 					// Preference
 					if preference.len() == 0 || preference == "-" {
 						continue;
 					}
 					
-					let preference: usize = preference.parse().expect("Syntax Error");
+					let preference: usize = preference.parse().context(format!("Invalid number \"{}\" at row {}, column {}", preference, csv_row + 2, csv_col + 1))?;
 					if preference == 0 {
 						continue;
 					}
@@ -73,7 +74,7 @@ pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequ
 				}
 				None => {
 					// $mult column
-					let mult: usize = preference.parse().expect("Syntax Error");
+					let mult: usize = preference.parse().context(format!("Invalid number \"{}\" at row {}, column {}", preference, csv_row + 2, csv_col + 1))?;
 					if mult == 1 {
 						continue;
 					}
@@ -131,7 +132,7 @@ pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequ
 		});
 	}
 	
-	return Election {
+	return Ok(Election {
 		name: String::new(),
 		seats: 0,
 		candidates: candidates,
@@ -139,5 +140,5 @@ pub fn parse_reader<R: Read, N: Number>(reader: R, require_1: bool, require_sequ
 		ballots: ballots,
 		total_votes: None,
 		constraints: None,
-	};
+	});
 }