Fix panic `trim_first_and_last_line_of_whitespace` on bad slice indices (#865)

* Fix panic from slice end being before slice start

* Fix fallback value for end index

Co-authored-by: XAMPPRocky <4464295+XAMPPRocky@users.noreply.github.com>

Cargo.lock

@@ -55,6 +55,21 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
+[[package]]
+name = "bit-set"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e11e16035ea35e4e5997b393eacbf6f63983188f7a2ad25bfb13465f5ad59de"
+dependencies = [
+ "bit-vec",
+]
+
+[[package]]
+name = "bit-vec"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "349f9b6a179ed607305526ca489b34ad0a41aed5f7980fa90eb03160b69598fb"
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
@@ -775,6 +790,38 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "proptest"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e0d9cc07f18492d879586c92b485def06bc850da3118075cd45d50e9c95b0e5"
+dependencies = [
+ "bit-set",
+ "bitflags",
+ "byteorder",
+ "lazy_static",
+ "num-traits",
+ "quick-error 2.0.1",
+ "rand",
+ "rand_chacha",
+ "rand_xorshift",
+ "regex-syntax",
+ "rusty-fork",
+ "tempfile",
+]
+
+[[package]]
+name = "quick-error"
+version = "1.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
+
+[[package]]
+name = "quick-error"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
+
 [[package]]
 name = "quote"
 version = "1.0.9"
@@ -824,6 +871,15 @@ dependencies = [
  "rand_core",
 ]
 
+[[package]]
+name = "rand_xorshift"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
+dependencies = [
+ "rand_core",
+]
+
 [[package]]
 name = "rayon"
 version = "1.5.1"
@@ -894,6 +950,18 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "rusty-fork"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb3dcc6e454c328bb824492db107ab7c0ae8fcffe4ad210136ef014458c1bc4f"
+dependencies = [
+ "fnv",
+ "quick-error 1.2.3",
+ "tempfile",
+ "wait-timeout",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.6"
@@ -1157,6 +1225,7 @@ dependencies = [
  "num-format",
  "once_cell",
  "parking_lot",
+ "proptest",
  "rayon",
  "regex",
  "serde",
@@ -1302,6 +1371,15 @@ version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
 
+[[package]]
+name = "wait-timeout"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.3.2"

Cargo.toml

@@ -75,6 +75,7 @@ optional = true
 version = "0.8.15"
 
 [dev-dependencies]
+proptest = "1.0.0"
 strum = "0.23.0"
 strum_macros = "0.23.0"
 regex = "1.4.6"

src/utils/ext.rs

@@ -38,9 +38,10 @@ impl SliceExt for [u8] {
             .iter()
             .rposition(|c| c.is_line_ending_whitespace() || !c.is_whitespace())
             .map_or_else(
-                || self.len(),
+                || self.len().saturating_sub(1),
                 |i| {
-                    if self[i.saturating_sub(1)] == b'\r' {
+                    // Remove the entire `\r\n` in the case that it was the line ending whitespace
+                    if self[i.saturating_sub(1)] == b'\r' && self[i] == b'\n' {
                         i - 1
                     } else {
                         i
@@ -114,6 +115,8 @@ impl SliceExt for [u8] {
 mod tests {
     use super::*;
 
+    use proptest::prelude::*;
+
     #[test]
     fn is_whitespace() {
         assert!(b' '.is_whitespace());
@@ -142,4 +145,19 @@ mod tests {
         assert!([1, 2, 3, 4, 5].contains_slice(&[2, 3, 4]));
         assert!(![1, 2, 3, 4, 5].contains_slice(&[]));
     }
+
+    #[test]
+    fn trim_first_and_last_line_of_whitespace_edge_cases() {
+        assert_eq!(b"", b"\ra ".trim_first_and_last_line_of_whitespace());
+        assert_eq!(b"a", b"\r\na ".trim_first_and_last_line_of_whitespace());
+
+        assert_eq!(b" ", b" ".trim_first_and_last_line_of_whitespace());
+    }
+
+    proptest! {
+        #[test]
+        fn trim_first_and_last_line_of_whitespace_doesnt_panic(input: Vec<u8>) {
+            let _ = &input.trim_first_and_last_line_of_whitespace();
+        }
+    }
 }