fuzzing: fix artifact path and experimental parser flags

Fix two issues in fuzzing infrastructure:
- Correct artifact upload path from promql/testdata/fuzz to util/fuzzing/testdata/fuzz to match where Go stores crash artifacts
- Fix GetCorpusForFuzzParseExpr to preserve original parser flag values instead of always resetting them to false, which was disabling experimental features before actual fuzzing ran

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>

.github/workflows/fuzzing.yml

@@ -29,7 +29,7 @@ jobs:
         if: failure()
         with:
           name: fuzz-artifacts-${{ matrix.fuzz_test }}
-          path: promql/testdata/fuzz/${{ matrix.fuzz_test }}
+          path: util/fuzzing/testdata/fuzz/${{ matrix.fuzz_test }}
   fuzzing_status:
     # This status check aggregates the individual matrix jobs of the fuzzing
     # step into a final status. Fails if a single matrix job fails, succeeds if

util/fuzzing/corpus.go

@@ -58,15 +58,17 @@ func GetCorpusForFuzzParseMetricSelector() []string {
 
 // GetCorpusForFuzzParseExpr returns the seed corpus for FuzzParseExpr.
 func GetCorpusForFuzzParseExpr() ([]string, error) {
+	// Save original values and restore them after parsing test expressions.
+	defer func(funcs, durationExpr, rangeSelectors bool) {
+		parser.EnableExperimentalFunctions = funcs
+		parser.ExperimentalDurationExpr = durationExpr
+		parser.EnableExtendedRangeSelectors = rangeSelectors
+	}(parser.EnableExperimentalFunctions, parser.ExperimentalDurationExpr, parser.EnableExtendedRangeSelectors)
+
 	// Enable experimental features to parse all test expressions.
 	parser.EnableExperimentalFunctions = true
 	parser.ExperimentalDurationExpr = true
 	parser.EnableExtendedRangeSelectors = true
-	defer func() {
-		parser.EnableExperimentalFunctions = false
-		parser.ExperimentalDurationExpr = false
-		parser.EnableExtendedRangeSelectors = false
-	}()
 
 	// Get built-in test expressions.
 	builtInExprs, err := promqltest.GetBuiltInExprs()