I came across an issue in my code and after a hard debug session I
found something that smells.
First the context of my issue. I have a AR object that has a
polymorphic belongs_to currently tied to nothing, I want to dump it to
YAML.
record.to_yaml
This raises the following exception:
TypeError: wrong argument type nil (expected Data)
from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/
lib/ruby/1.8/yaml.rb:391:in `emit'
from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/
lib/ruby/1.8/yaml.rb:391:in `quick_emit'
from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/
lib/ruby/1.8/yaml/rubytypes.rb:15:in `to_yaml'
Now to the point: tracing the code path lead me to
AssociationProxy#method_missing which for 2.3.x or 3.0.x is very
similar:
def method_missing(method, *args)
if load_target
unless @target.respond_to?(method)
message = "undefined method `#{method.to_s}' for
\"#{@target}\":#{@target.class.to_s}"
raise NoMethodError, message
end
if block_given?
@target.send(method, *args) { |*block_args|
yield(*block_args) }
else
@target.send(method, *args)
end
end
end
The smell: load_target may return nil, when it does, the return value
of method_missing is nil. BUT the caller may have wanted to call a
method on nil. Like #to_yaml !
The caller (in this case something in YAML) expects some data back
from nil.to_yaml (a string) but it receives nil which later raises the
exception.
What about that?
Regards,
Pascal
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