add transactional semantics to rustfix

Author: saites

crates/rustfix/src/error.rs

@@ -2,6 +2,7 @@
 
 use std::ops::Range;
 
+#[non_exhaustive]
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
     #[error("invalid range {0:?}, start is larger than end")]
@@ -10,9 +11,7 @@ pub enum Error {
     #[error("invalid range {0:?}, original data is only {1} byte long")]
     DataLengthExceeded(Range<usize>, usize),
 
-    #[error("could not replace range {0:?}, maybe parts of it were already replaced?")]
-    MaybeAlreadyReplaced(Range<usize>),
-
+    #[non_exhaustive] // There are plans to add fields to this variant at a later time.
     #[error("cannot replace slice of data that was already replaced")]
     AlreadyReplaced,
 

crates/rustfix/src/lib.rs

@@ -243,9 +243,11 @@ impl CodeFix {
     pub fn apply_solution(&mut self, solution: &Solution) -> Result<(), Error> {
         for r in &solution.replacements {
             self.data
-                .replace_range(r.snippet.range.clone(), r.replacement.as_bytes())?;
-            self.modified = true;
+                .replace_range(r.snippet.range.clone(), r.replacement.as_bytes())
+                .inspect_err(|_| self.data.restore())?;
         }
+        self.data.commit();
+        self.modified = true;
         Ok(())
     }