From c08eb9163251a4a6e20812d392c7ddd93cfd90c3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vin=C3=ADcius=20Miguel?= <lemao.vrm07@hotmail.com>
Date: Wed, 7 Apr 2021 21:59:23 -0300
Subject: [PATCH] oof: add some error variants to replace panics

---
 oof/src/error.rs | 10 +++++++++-
 oof/src/lib.rs   | 24 +++++++++++-------------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/oof/src/error.rs b/oof/src/error.rs
index abc8671..3403771 100644
--- a/oof/src/error.rs
+++ b/oof/src/error.rs
@@ -3,12 +3,17 @@ use std::{error, ffi::OsString, fmt};
 use crate::Flag;
 
 #[derive(Debug)]
-pub enum OofError {
+pub enum OofError{
     FlagValueConflict {
         flag: Flag,
         previous_value: OsString,
         new_value: OsString,
     },
+    /// User supplied a flag containing invalid Unicode
+    InvalidUnicode(OsString),
+    /// User supplied an unrecognized short flag
+    UnknownShortFlag(char),
+    MisplacedShortArgFlagError(char)
 }
 
 impl error::Error for OofError {
@@ -30,6 +35,9 @@ impl fmt::Display for OofError {
                 "CLI flag value conflicted for flag '--{}', previous: {:?}, new: {:?}.",
                 flag.long, previous_value, new_value
             ),
+            OofError::InvalidUnicode(flag) => write!(f, "{:?} is not valid Unicode.", flag),
+            OofError::UnknownShortFlag(ch) => write!(f, "Unknown argument '-{}'", ch),
+            OofError::MisplacedShortArgFlagError(ch) => write!(f, "Invalid placement of `-{}`.\nOnly the last letter in a sequence of short flags can take values.", ch),
         }
     }
 }
diff --git a/oof/src/lib.rs b/oof/src/lib.rs
index ccd4364..ef509ac 100644
--- a/oof/src/lib.rs
+++ b/oof/src/lib.rs
@@ -7,10 +7,7 @@ mod error;
 mod flags;
 pub mod util;
 
-use std::{
-    collections::BTreeMap,
-    ffi::{OsStr, OsString},
-};
+use std::{collections::BTreeMap, ffi::{OsStr, OsString}};
 
 pub use error::OofError;
 pub use flags::{ArgFlag, Flag, FlagType, Flags};
@@ -105,10 +102,11 @@ pub fn filter_flags(
             continue;
         }
 
-        // If it is a flag, now we try to interpret as valid utf-8
-        let flag: &str = arg
-            .to_str()
-            .unwrap_or_else(|| panic!("User error: The flag needs to be valid utf8"));
+        // If it is a flag, now we try to interpret it as valid utf-8
+        let flag= match arg.to_str() {
+            Some(arg) => arg,
+            None => return Err(OofError::InvalidUnicode(arg))
+        };
 
         // Only one hyphen in the flag
         // A short flag can be of form "-", "-abcd", "-h", "-v", etc
@@ -129,14 +127,14 @@ pub fn filter_flags(
                 // Safety: this loop only runs when len >= 1, so this subtraction is safe
                 let is_last_letter = i == letters.len() - 1;
 
-                let flag_info = short_flags_info.get(&letter).unwrap_or_else(|| {
-                    panic!("User error: Unexpected/UNKNOWN flag `letter`, error")
-                });
+                let flag_info = short_flags_info.get(&letter).ok_or_else(|| {
+                    OofError::UnknownShortFlag(letter)
+                })?;
 
                 if !is_last_letter && flag_info.takes_value {
-                    panic!("User error: Only the last letter can refer to flag that takes values");
+                    return Err(OofError::MisplacedShortArgFlagError(letter))
                     // Because "-AB argument" only works if B takes values, not A.
-                    // That is, the short flag that takes values need to come at the end
+                    // That is, the short flag that takes values needs to come at the end
                     // of this piece of text
                 }