[PATCH v4] scripts: checkpatch: warn on Rust panicking methods

[Jason Hall]

Add regex check in checkpatch.pl for common Rust panicking methods
like unwrap() and expect().

Allow an exception if the line contains a '// PANIC:' comment.

Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Link: https://github.com/Rust-for-linux/linux/issues/1191
Signed-off-by: Jason Hall <jason.kei.hall@xxxxxxxxx>
---
Hi Dirk,

Now using imperative mood.  I decided to keep that logic stateless
unless its agreed that we need to add state.  Adding checks for #[test]
and other test identifiers will make this much more complicated.  There
is already a check for // PANIC: that works fine.

v4:
 - Use imperative mood in commit description.
 - Fix patch formatting and placement of '---' separator.
v3:
 - Use non-capturing groups (?:) to optimize regex.
v2:
 - Switch from \b to (\.|::) to avoid false positives in strings.
 - Add : to PANIC comment check.

 scripts/checkpatch.pl | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index c0250244cf7a..37bdf602e7e7 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3834,6 +3834,17 @@ sub process {
 # check we are in a valid source file if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|rs|s|S|sh|dtsi|dts)$/);
 
+# check for Rust unwrap/expect
+		if ($realfile =~ /\.rs$/ && $line =~ /^\+/) {
+			if ($line =~ /(?:\.|::)(?:unwrap|expect)\s*\(/ &&
+				$rawline !~ /\/\/\s*PANIC:/ &&
+				$line !~ /^\+\s*\/\// &&
+				$line !~ /^\+\s*assert/) {
+				WARN("RUST_UNWRAP",
+					"Avoid unwrap() or expect() in Rust code; use proper error handling (Result) or justify with a '// PANIC: ...' comment.\n" . $herecurr);
+			}
+		}
+
 # check for using SPDX-License-Identifier on the wrong line number
 		if ($realline != $checklicenseline &&
 		    $rawline =~ /\bSPDX-License-Identifier:/ &&
-- 
2.43.0