Function which calculates time from now to end date - strange warning from VSCode

Do you have another function which pattern matches for nil ?

def time_remaining(nil), do: # do something 

if you don’t have it may be you can rewrite it this way to handle nil:

def time_remaining(nil),  do: # do something return an error or empty string 
def time_remaining(ends_at) do
    days_remaining = NaiveDateTime.diff(ends_at, NaiveDateTime.utc_now(), :day)

    if days_remaining < 1 do
      difference = NaiveDateTime.diff(ends_at, NaiveDateTime.utc_now(), :second)
      hours = div(difference, 3600)
      minutes = div(difference, 60) - (hours * 60)
      seconds = rem(difference, 60)

      "#{hours}h : #{minutes}min : #{seconds}s Remaining"
    else
      "#{days_remaining} Days Remaining"
    end
  end

Thanks for checking it out, unfortunately, nil handling doesn’t help, the warning remains.

What happens when you invoke function time_remaining with nil ?

What version of Elixir are you using? I get no warnings when I compile in 1.14.1.

Regardless, since ends_at must be a NaiveDateTime, it’s better to be explicit about this in the function head as opposed to just checking that it isn’t nil:

def time_remaining(%NaiveDateTime{} = ends_at) do
  ...
end

or if you prefer when you can do the more verbose:

def time_remaining(ends_at) when is_struct(ends_at, NaiveDateTime) do
  ...
end

Sure that is coming from this function?
Would expect sth like ends_at@... here.

I haven’t seen this type of Dialyzer warning on a guard call before; but I have seen similar warnings for function parameters when Dialyzer thinks there’s no way for a given pattern match to possibly match a condition… which I sometimes do for a catch all function.

For example if I write something like the below, with no other calls to func_a/1:

def entry_func() do
  %{test: "Hi!"}
  |> func_a()
end

def func_a(%{} = param) do
  # do something
end

def func_a(_) do
  raise "Bad Param"
end

I will, with some regularity, see the ElixirLS Dialyzer warning that the second function head for func_a will never run… which looks like it could be similar to what you’re seeing. In this case Dialyzer isn’t exactly wrong… there’s no way for the second func_a/1 function head to match. But it’s not exactly helpful either because I may know now that in the future I might call it from somewhere else where the second function head is helpful.

Anyway, I can’t say for sure this is what you’re seeing, but it looks similar.

I don’t think the error is in the time_remaining function shown; the success typing in the error message doesn’t match anything that would appear inside that function.

It’s instead a synonym for Phoenix.HTML.safe. Maybe there’s a when not is_nil check someplace in the template near where this is used?

@Sebb
Sure that is coming from this function?
Would expect sth like ends_at@... here.

@al2o3cr
I don’t think the error is in the time_remaining function shown; the success typing in the error message doesn’t match anything that would appear inside that function.

Yes, it looks like something else is happening here… if I remove the logic from this function and make it to return just a simple string, VSCode still shows the same error but starts highlighting the code in another function so the error is probably somewhere else,=. I will isolate each function from that view and and try to find the problem that way. Thanks for your help.

yes, @al2o3cr is right, didn’t look that closely.

You can try to delete the .elixir-ls folder and restart/reload vscode.
Sometimes there is a hickup.
And maybe install dilyxir and run mix dialyzer to get a better picture.

Deleting .elixir_ls folder solved it, thanks for taking the time to help me out here.