Strip out control codes from the logged messages (#10081)

* Strip out control codes from the logged messages

* Also strip away C1 control codes

* Add extra comments

* Clear the buffer after flushing; rename `write` to `flush`

* Move control code stripping into its own function

* Also strip out control codes from panic messages

* Also strip out Unicode left-to-right/right-to-left control codes

substrate/client/tracing/src/logging/mod.rs

@@ -595,4 +595,36 @@ mod tests {
 			assert!(stderr.contains(&line));
 		}
 	}
+
+	#[test]
+	fn control_characters_are_always_stripped_out_from_the_log_messages() {
+		const RAW_LINE: &str = "$$START$$\x1B[1;32mIn\u{202a}\u{202e}\u{2066}\u{2069}ner\n\r\x7ftext!\u{80}\u{9f}\x1B[0m$$END$$";
+		const SANITIZED_LINE: &str = "$$START$$Inner\ntext!$$END$$";
+
+		let output = run_test_in_another_process(
+			"control_characters_are_always_stripped_out_from_the_log_messages",
+			|| {
+				std::env::set_var("RUST_LOG", "trace");
+				let mut builder = LoggerBuilder::new("");
+				builder.with_colors(true);
+				builder.init().unwrap();
+				log::error!("{}", RAW_LINE);
+			},
+		);
+
+		if let Some(output) = output {
+			let stderr = String::from_utf8(output.stderr).unwrap();
+			// The log messages should always be sanitized.
+			assert!(!stderr.contains(RAW_LINE));
+			assert!(stderr.contains(SANITIZED_LINE));
+
+			// The part where the timestamp, the logging level, etc. is printed out doesn't
+			// always have to be sanitized unless it's necessary, and here it shouldn't be.
+			assert!(stderr.contains("\x1B[31mERROR\x1B[0m"));
+
+			// Make sure the logs aren't being duplicated.
+			assert_eq!(stderr.find("ERROR"), stderr.rfind("ERROR"));
+			assert_eq!(stderr.find(SANITIZED_LINE), stderr.rfind(SANITIZED_LINE));
+		}
+	}
 }