fix(fuzz): exclude skipped corpus inputs

.changelog/skip-skipped-fuzz-corpus.md

@@ -0,0 +1,5 @@
+---
+forge: patch
+---
+
+Prevent stateless inputs discarded by `vm.skip` from contributing coverage or being persisted to the fuzz corpus.

crates/evm/evm/src/executors/fuzz/mod.rs

@@ -444,18 +444,28 @@ impl<FEN: FoundryEvmNetwork> FuzzedExecutor<FEN> {
             return Err(TestCaseError::reject(FuzzError::AssumeReject));
         }
 
-        let new_coverage = coverage_metrics.merge_edge_coverage(&mut call);
-        // `new_coverage` is only meaningful when edge coverage is collected; otherwise
-        // `merge_edge_coverage` always returns `false`, so record it as unknown for frontiers.
-        let frontier_new_coverage =
-            self.config.corpus.collect_edge_coverage().then_some(new_coverage);
-        frontier_recorder.capture_stateless_call(fuzz_run, &tx, &cmp_values, frontier_new_coverage);
-        coverage_metrics.process_inputs(
-            std::slice::from_ref(&tx),
-            &[cmp_values],
-            new_coverage,
-            None,
-        );
+        if call.skip_reason().is_some() {
+            // Account for the attempted corpus mutation without retaining or crediting the input.
+            coverage_metrics.process_inputs(&[], &[], false, None);
+        } else {
+            let new_coverage = coverage_metrics.merge_edge_coverage(&mut call);
+            // `new_coverage` is only meaningful when edge coverage is collected; otherwise
+            // `merge_edge_coverage` always returns `false`, so record it as unknown for frontiers.
+            let frontier_new_coverage =
+                self.config.corpus.collect_edge_coverage().then_some(new_coverage);
+            frontier_recorder.capture_stateless_call(
+                fuzz_run,
+                &tx,
+                &cmp_values,
+                frontier_new_coverage,
+            );
+            coverage_metrics.process_inputs(
+                std::slice::from_ref(&tx),
+                &[cmp_values],
+                new_coverage,
+                None,
+            );
+        }
 
         let (breakpoints, deprecated_cheatcodes) =
             call.cheatcodes.as_ref().map_or_else(Default::default, |cheats| {

crates/forge/tests/cli/test_cmd/fuzz.rs

@@ -744,6 +744,31 @@ contract ForgeFuzzReplayFailureTest {
     assert!(stdout.contains("[SKIP: not runnable in replay mode] test_unit()"), "{stdout}");
 });
 
+forgetest_init!(stateless_fuzz_does_not_persist_skips, |prj, cmd| {
+    let corpus_root = prj.root().join("fuzz_corpus");
+    prj.update_config(|config| {
+        config.fuzz.runs = 1;
+        config.fuzz.seed = Some(U256::from(1));
+        config.fuzz.corpus.corpus_dir = Some(corpus_root.clone());
+    });
+    prj.add_test(
+        "StatelessSkip.t.sol",
+        r#"
+import {Test} from "forge-std/Test.sol";
+
+contract StatelessSkipTest is Test {
+    function testFuzz_skip(uint256) public {
+        vm.skip(true);
+    }
+}
+   "#,
+    );
+
+    cmd.args(["test", "--mt", "testFuzz_skip", "-q"]).assert_success();
+
+    assert!(!has_regular_file(&corpus_root));
+});
+
 forgetest_init!(stateless_fuzz_does_not_persist_assume_rejects, |prj, cmd| {
     let corpus_root = prj.root().join("fuzz_corpus");
     prj.update_config(|config| {