Add parser and runtime fuzz targets

Author: mgomes

ROADMAP.md

@@ -329,7 +329,7 @@ Goal: improve day-to-day developer productivity and interpreter robustness.
 - [ ] Profile evaluator hotspots and optimize dispatch paths.
 - [ ] Reduce allocations in common value transformations.
 - [ ] Improve error rendering for deeply nested call stacks.
-- [ ] Add fuzz tests for parser and runtime edge cases.
+- [x] Add fuzz tests for parser and runtime edge cases.
 
 ### CI and Release Engineering
 

vibes/fuzz_test.go

@@ -0,0 +1,67 @@
+package vibes
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+func FuzzCompileScriptDoesNotPanic(f *testing.F) {
+	f.Add([]byte(""))
+	f.Add([]byte("def run() 1 end"))
+	f.Add([]byte("def broken("))
+	f.Add([]byte("begin\n  raise(\"boom\")\nrescue\n  1\nend"))
+	f.Add([]byte("require(\"../path\")"))
+
+	f.Fuzz(func(t *testing.T, raw []byte) {
+		engine := MustNewEngine(Config{})
+		_, _ = engine.Compile(string(raw))
+	})
+}
+
+func FuzzRuntimeEdgeCasesDoNotPanic(f *testing.F) {
+	engine := MustNewEngine(Config{})
+	script, err := engine.Compile(`
+def run(text, pattern)
+  stable_groups = text.split("").group_by_stable do |char|
+    if char == ""
+      :empty
+    else
+      :present
+    end
+  end
+
+  {
+    match: Regex.match(pattern, text),
+    replace_all: Regex.replace_all(text, pattern, "x"),
+    json: JSON.stringify({ text: text }),
+    template: "value={{text}}".template({ text: text }),
+    chunks: text.split("").chunk(4),
+    windows: text.split("").window(2),
+    stable_groups: stable_groups
+  }
+end
+`)
+	if err != nil {
+		f.Fatalf("compile failed: %v", err)
+	}
+
+	f.Add("", "a*")
+	f.Add("ID-12 ID-34", "ID-[0-9]+")
+	f.Add(strings.Repeat("a", 256), "(")
+	f.Add("  hello \n world  ", "\\s+")
+	f.Add("{}", ".*")
+
+	f.Fuzz(func(t *testing.T, text string, pattern string) {
+		if len(text) > 4096 {
+			text = text[:4096]
+		}
+		if len(pattern) > 1024 {
+			pattern = pattern[:1024]
+		}
+		_, _ = script.Call(context.Background(), "run", []Value{
+			NewString(text),
+			NewString(pattern),
+		}, CallOptions{})
+	})
+}