[erlang-questions] Dialyzer

[Kostis Sagonas]

Carlo Bertoldi wrote:
> On 02/05/2011 11:23, Kostis Sagonas wrote:
>> Carlo Bertoldi wrote:
>>> Hello list,
>>>  this is a bad monday, and I'm stuck with this warning from dialyzer:
>>>
>>> The specification for change_interval/2 states that the function 
>>> might also return [any()] but the inferred return is none()
>>>
>>> The code:
>>> -spec(change_interval(integer(), [term()]) -> [term()]).
>>>
>>> change_interval(NewInterval, Config) ->
>>>     NewPause = {pause, NewInterval},
>>>     NewConfig = lists:keyreplace(pause, 1, Config, NewPause),
>>>     write_config(NewPause),
>>>     NewConfig.
>>>
> I apologize for the incompleteness, here goes the module

Well, probably it's a bad Monday alright for you.  Wondering what 
exactly it is you did during the weekend... ;)

Anyway, didn't you happen to notice that dialyzer generates an awful lot 
of other warnings for this module?  Among them, a warning that basically 
tells you that the proper way to use file:open/2 is with a list of 
options in the second argument, i.e. file:open(File, [write]), instead 
of what you've written below?  Please fix this.

As to the warning you are getting, can't you see that the function 
change_interval/2 is nowhere used in this file?  Even erlc will tell you 
that.

Kostis

> -module(test).
> -export([test_write_config/0]).
> 
> -define(PAUSE_FILE, "test.conf").
> 
> -spec(change_interval(integer(), [term()]) -> [term()]).
> 
> change_interval(NewInterval, Config) ->
>     NewPause = {pause, NewInterval},
>     NewConfig = lists:keyreplace(pause, 1, Config, NewPause),
>     write_config(NewPause),
>     NewConfig.
> 
> -spec(write_config(tuple(pause, integer())) -> ok | error).
> write_config(Pause) ->
>     File = ?PAUSE_FILE,
>     case file:open(File, write) of
>         {ok , F} ->
>             io:format(F, "~w.", [Pause]),
>             file:close(F),
>             ok;
>         {error, Reason}    ->
>             io:format("Error opening file ~p: ~p~n", [File, Reason]),
>             error
>     end.
> 
> test_write_config() ->
>     Pause = {pause, 6767576},
>     write_config(Pause),
>     {ok, Config} = file:consult(?PAUSE_FILE),
>     Config.