Collapse mocking_utils into one.

Signed-off-by: Michel Hidalgo <michel@ekumenlabs.com>

rcl/test/mocking_utils/patch.hpp

@@ -219,11 +219,8 @@ class Patch<ID, ReturnT(ArgTs...)>
    * \return a mocking_utils::Patch instance.
    */
   explicit Patch(const std::string & target, std::function<ReturnT(ArgTs...)> proxy)
-  : proxy_(proxy)
+  : target_(target), proxy_(proxy)
   {
-    auto MMK_MANGLE(mock_type, create) =
-      PatchTraits<ID, ReturnT(ArgTs...)>::MMK_MANGLE(mock_type, create);
-    mock_ = mmk_mock(target.c_str(), mock_type);
   }
 
   // Copy construction and assignment are disabled.
@@ -255,18 +252,14 @@ class Patch<ID, ReturnT(ArgTs...)>
   /// Inject a @p replacement for the patched function.
   Patch & then_call(std::function<ReturnT(ArgTs...)> replacement) &
   {
-    auto type_erased_trampoline =
-      reinterpret_cast<mmk_fn>(prepare_trampoline<ID>(replacement));
-    mmk_when(proxy_(any<ArgTs>()...), .then_call = type_erased_trampoline);
+    replace_with(replacement);
     return *this;
   }
 
   /// Inject a @p replacement for the patched function.
   Patch && then_call(std::function<ReturnT(ArgTs...)> replacement) &&
   {
-    auto type_erased_trampoline =
-      reinterpret_cast<mmk_fn>(prepare_trampoline<ID>(replacement));
-    mmk_when(proxy_(any<ArgTs>()...), .then_call = type_erased_trampoline);
+    replace_with(replacement);
     return std::move(*this);
   }
 
@@ -276,7 +269,21 @@ class Patch<ID, ReturnT(ArgTs...)>
   template<typename T>
   T any() {return mmk_any(T);}
 
-  mock_type mock_;
+  void replace_with(std::function<ReturnT(ArgTs...)> replacement)
+  {
+    if (mock_) {
+      throw std::logic_error("Cannot configure patch more than once");
+    }
+    auto type_erased_trampoline =
+      reinterpret_cast<mmk_fn>(prepare_trampoline<ID>(replacement));
+    auto MMK_MANGLE(mock_type, create) =
+      PatchTraits<ID, ReturnT(ArgTs...)>::MMK_MANGLE(mock_type, create);
+    mock_ = mmk_mock(target_.c_str(), mock_type);
+    mmk_when(proxy_(any<ArgTs>()...), .then_call = type_erased_trampoline);
+  }
+
+  mock_type mock_{nullptr};
+  std::string target_;
   std::function<ReturnT(ArgTs...)> proxy_;
 };
 
@@ -332,15 +339,29 @@ auto make_patch(const std::string & target, std::function<SignatureT> proxy)
 #define MOCKING_UTILS_PATCH_TARGET(scope, function) \
   (std::string(RCUTILS_STRINGIFY(function)) + "@" + (scope))
 
-/// Patch a `function` with a used-provided `replacement` in a given `scope`.
-#define patch(scope, function, replacement) \
+/// Prepare a mocking_utils::Patch for patching a `function` in a given `scope`
+/// but defer applying any changes.
+#define prepare_patch(scope, function) \
   make_patch<__COUNTER__, decltype(function)>( \
     MOCKING_UTILS_PATCH_TARGET(scope, function), MOCKING_UTILS_PATCH_PROXY(function) \
-  ).then_call(replacement)
+  )
 
-/// Patch a function with a function that only returns a value
-#define patch_and_return(scope, function, return_value) \
-  patch(scope, function, [&](auto && ...) {return return_value;})
+/// Patch a `function` with a used-provided `replacement` in a given `scope`.
+#define patch(scope, function, replacement) \
+  prepare_patch(scope, function).then_call(replacement)
+
+/// Patch a `function` to always yield a given `return_code` in a given `scope`.
+#define patch_and_return(scope, function, return_code) \
+  patch(scope, function, [&](auto && ...) {return return_code;})
+
+/// Patch a `function` to execute normally but always yield a given `return_code`
+/// in a given `scope`.
+#define inject_on_return(scope, function, return_code) \
+  patch( \
+    scope, function, ([&, base = function](auto && ... __args) { \
+      static_cast<void>(base(std::forward<decltype(__args)>(__args)...)); \
+      return return_code; \
+    }))
 
 }  // namespace mocking_utils