Elixir: Integer.parse/2 raises FunctionClauseError on count_digits/2 when given nil

[CaldwellYSR]

Current behavior

Integer.parse(nil)

** (FunctionClauseError) no function clause matching in Integer.count_digits/2

Expected behavior

Return :error so we can pattern match on it instead of crashing.

[NobbZ]

Passing nil to it is violating the contract, so raising is fine I think.

[CaldwellYSR]

Is there a better way to parse to an integer then? String.to_integer/1 raises when given nil as well. I could pattern match the nil out ahead of time but in my use case that isn't very DRY and it would feel better to get :error from the parser.

[josevalim]

@CaldwellYSR you should check for nil then. Create a function called parse_integer_or_nil that handles it for you.

The :error tuple is only about error in parsing for valid values. For example, if I pass an integer to File.read, I want it to fail, because that's a logical error. I don't want it to say badarg.

[OvermindDL1]

@CaldwellYSR For note, you really should be using dialyzer (like via the Dialyxir plugin on hex.pm makes it super easy) as it would have caught such typing issues unless your specs are incorrect yourself. It is highly recommended to use.