fix(fmt): write files on disk only if they're not perfect match (#8775)

* fix(fmt): write files on disk only if they're not perfect match

* Cleanup

Author: grandizzy

crates/fmt/src/formatter.rs

@@ -1246,7 +1246,7 @@ impl<'a, W: Write> Formatter<'a, W> {
             })?;
 
             write_chunk!(self, "}}")?;
-            return Ok(true)
+            return Ok(false)
         }
 
         // Determine writable statements by excluding statements from disabled start / end lines.

crates/fmt/testdata/Repros/fmt.sol

@@ -139,8 +139,7 @@ contract IfElseTest {
             number = 1;
         } else if (newNumber = 2) {
             //            number = 2;
-        }
-        else {
+        } else {
             newNumber = 3;
         }
     }

crates/forge/bin/cmd/fmt.rs

@@ -125,17 +125,22 @@ impl FmtArgs {
                 )
             })?;
 
+            let diff = TextDiff::from_lines(&source, &output);
+            let new_format = diff.ratio() < 1.0;
             if self.check || path.is_none() {
                 if self.raw {
                     print!("{output}");
                 }
 
-                let diff = TextDiff::from_lines(&source, &output);
-                if diff.ratio() < 1.0 {
+                // If new format then compute diff summary.
+                if new_format {
                     return Ok(Some(format_diff_summary(&name, &diff)))
                 }
             } else if let Some(path) = path {
-                fs::write(path, output)?;
+                // If new format then write it on disk.
+                if new_format {
+                    fs::write(path, output)?;
+                }
             }
             Ok(None)
         };

testdata/default/fuzz/invariant/common/InvariantPreserveState.t.sol

@@ -15,8 +15,9 @@ contract Handler is DSTest {
     Vm constant vm = Vm(HEVM_ADDRESS);
 
     function thisFunctionReverts() external {
-        if (block.number < 10) {}
-        else revert();
+        if (block.number < 10) {} else {
+            revert();
+        }
     }
 
     function advanceTime(uint256 blocks) external {