pkg/aflow/tool/codeeditor: add package

Code editing tool stub.
Update #6470

Author: dvyukov

pkg/aflow/tool/codeeditor/codeeditor.go

@@ -0,0 +1,37 @@
+// Copyright 2026 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package codeeditor
+
+import (
+	"github.com/google/syzkaller/pkg/aflow"
+)
+
+var Tool = aflow.NewFuncTool("codeeditor", codeeditor, `
+The tool does one code edit to form the final patch.
+The tool should be called mutiple times to do all required changes one-by-one,
+but avoid changing the same lines multiple times.
+Note: You will not see your edits via the codesearch tool.
+Note: The current code snippet should reflect the previous changes.
+`)
+
+type state struct {
+	KernelScratchSrc string
+}
+
+type args struct {
+	SourceFile  string `jsonschema:"Full source file path."`
+	CurrentCode string `jsonschema:"The current code to replace verbatim with new lines, but without line numbers."`
+	NewCode     string `jsonschema:"New code to replace the current code snippet."`
+}
+
+func codeeditor(ctx *aflow.Context, state state, args args) (struct{}, error) {
+	// TODO: check that the SourceFile is not escaping.
+	// If SourceFile is incorrect, or CurrentCode is not matched, return aflow.BadCallError
+	// with an explanation. Say that it needs to increase context if CurrentCode is not matched.
+	// Try to do as fuzzy match for CurrentCode as possible (strip line numbers,
+	// ignore white-spaces, etc).
+	// Should we accept a reference line number, or function name to disambiguate in the case
+	// of multiple matches?
+	return struct{}{}, nil
+}