Pattern matching in stubbed functions does not record call args correctly

[wanderanimrod]

Current behaviour

All within an exunit test context

with_mock(mock) = defmock_of RealModule do
  def is_age_one?(%{age: 1}) do
     {:ok, "age is one"}
  end

  def is_age_one?(%{age: age}) do
    {:error, "age is not one. it is #{age}"}
  end
end

response = mock.is_age_one? %{age: 1, height: 1.74}
assert response == {:ok, "age is one"} #should pass

assert_called mock.is_age_one?(%{age: 1, height: 1.74})
# this fails, only recording the section of the arg in the 
# function's pattern match which is: %{age: 1}

This could also imply that pattern matching with functions in mock definitions does not work correctly, particularly with maps, and possibly with other data structures.

[wanderanimrod]

Stumbled into a workaround for this bug. When defining functions that take maps as arguments within mocks, assign the whole map to a variable.

with_mock(mock) = defmock_of RealModule do
  def is_age_one?(%{age: 1} = _dummy_var) do
     {:ok, "age is one"}
  end
  
  # instead of
  def is_age_one?(%{age: 1}) do
     {:ok, "age is one"}
  end
end

For some reason, this fixes it. Will investigate more if this workaround doesn't work for you.