Tweak prefix match to use .all_rules() (#5512)

## Summary

No behavior change, but I think this is a little cleaner.

crates/ruff/src/codes.rs

@@ -14,6 +14,18 @@ use crate::rules;
 #[derive(PartialEq, Eq, PartialOrd, Ord)]
 pub struct NoqaCode(&'static str, &'static str);
 
+impl NoqaCode {
+    /// Return the prefix for the [`NoqaCode`], e.g., `SIM` for `SIM101`.
+    pub fn prefix(&self) -> &str {
+        self.0
+    }
+
+    /// Return the suffix for the [`NoqaCode`], e.g., `101` for `SIM101`.
+    pub fn suffix(&self) -> &str {
+        self.1
+    }
+}
+
 impl std::fmt::Debug for NoqaCode {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         std::fmt::Display::fmt(self, f)

crates/ruff/src/registry.rs

@@ -18,23 +18,17 @@ pub trait AsRule {
 impl Rule {
     pub fn from_code(code: &str) -> Result<Self, FromCodeError> {
         let (linter, code) = Linter::parse_code(code).ok_or(FromCodeError::Unknown)?;
-        let prefix: RuleCodePrefix = RuleCodePrefix::parse(&linter, code)?;
-        let rule = prefix.rules().next().unwrap();
-        // TODO(charlie): Add a method to return an individual code, rather than matching on the
-        // prefix.
-        if rule.noqa_code().to_string() != format!("{}{}", linter.common_prefix(), code) {
-            return Err(FromCodeError::Prefix);
-        }
-        Ok(rule)
+        linter
+            .all_rules()
+            .find(|rule| rule.noqa_code().suffix() == code)
+            .ok_or(FromCodeError::Unknown)
     }
 }
 
 #[derive(thiserror::Error, Debug)]
 pub enum FromCodeError {
     #[error("unknown rule code")]
     Unknown,
-    #[error("expected a rule code (like `SIM101`), not a prefix (like `SIM` or `SIM1`)")]
-    Prefix,
 }
 
 #[derive(EnumIter, Debug, PartialEq, Eq, Clone, Hash, RuleNamespace)]