From a63609102ac90f0eb8e4f616bb5c28853c40d256 Mon Sep 17 00:00:00 2001
From: Henry Fredrick Schreiner <henry.fredrick.schreiner@cern.ch>
Date: Wed, 27 Jun 2018 17:55:42 +0200
Subject: [PATCH] Support empty lambdas

---
 include/CLI/Option.hpp | 10 ++++------
 tests/AppTest.cpp      | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/include/CLI/Option.hpp b/include/CLI/Option.hpp
index a1e65ffb..f594ca61 100644
--- a/include/CLI/Option.hpp
+++ b/include/CLI/Option.hpp
@@ -226,12 +226,10 @@ class Option : public OptionBase<Option> {
     ///@}
 
     /// Making an option by hand is not defined, it must be made by the App class
-    Option(std::string name,
-           std::string description = "",
-           std::function<bool(results_t)> callback = [](results_t) { return true; },
-           bool default_ = true,
-           App *parent = nullptr)
-        : description_(std::move(description)), default_(default_), parent_(parent), callback_(std::move(callback)) {
+    Option(
+        std::string name, std::string description, std::function<bool(results_t)> callback, bool default_, App *parent)
+        : description_(std::move(description)), default_(default_), parent_(parent),
+          callback_(callback ? std::move(callback) : [](results_t) { return true; }) {
         std::tie(snames_, lnames_, pname_) = detail::get_names(detail::split_names(name));
     }
 
diff --git a/tests/AppTest.cpp b/tests/AppTest.cpp
index 5697e634..1c6a969f 100644
--- a/tests/AppTest.cpp
+++ b/tests/AppTest.cpp
@@ -1472,3 +1472,23 @@ TEST_F(TApp, RepeatingMultiArgumentOptions) {
     args.pop_back();
     ASSERT_THROW(run(), CLI::ArgumentMismatch);
 }
+
+// #122
+TEST_F(TApp, EmptyOptionEach) {
+    std::string q;
+    app.add_option("--each", {})->each([&q](std::string s) { q = s; });
+
+    args = {"--each", "that"};
+    run();
+
+    EXPECT_EQ(q, "that");
+}
+
+// #122
+TEST_F(TApp, EmptyOptionFail) {
+    std::string q;
+    app.add_option("--each", {});
+
+    args = {"--each", "that"};
+    run();
+}