Feature request: drop insignificant zeros by default

[petrus-jvrensburg]

When displaying prices, it's common to only display subunits if they are present.

E.g. it would be preferable to display this value

iex(8)> Cldr.Number.to_string!(12345, locale: "hi-IN", currency: "INR")
"₹12,345.00"

as ₹12,345.

We could get this effect by rounding the number, but then it's not clear when we are throwing away information and when not. So I would argue that the subunits should be shown if present, so that the number can be rounded explicitly if that is the desired behaviour.

[kipcole9]

The formats are all driven by CLDR as you know. And preserving information is important as you say. The most straight forward is to format using :fractional_digits:

# Format the number without fractional digits
iex> Cldr.Number.to_string!(12345, locale: "en-IN", currency: "INR", fractional_digits: 0)
"₹12,345"

# If using `ex_money` then you can test if the amount is an integer and format accordingly
iex> m = Money.new(:INR, "12345.67")
iex> options = if Money.integer?(m), do: [fractional_digits: 0], else: []
iex> Money.to_string m, options

Of course a similar check for whether a number or Decimal is an integral value can also be calculated other ways.

[kipcole9]

There are also:

• Money.put_fraction/2 which allows forcing the fractional part of a number. For example, pricing often ends up being fractional 99 ( like $2.99) so this can be forced.
• Money.round/2 which has several different kinds of rounding.

[kipcole9]

Net, since I didn't answer your question, is that I believe ex_cldr_numbers should faithfully implement the CLDR formats as documented. If we look at what the format is for a currency for :en-IN we see:

iex> MyApp.Cldr.Number.Format.formats_for!(:"en-IN") |> Map.get(:currency)
"¤#,##,##0.00"

The fractional .00 zeros indicate, by definition, that these are required digits. If we want those digits to be optional we can use a different format (not built in):

# Use a format where the fractional digits are optional
iex> Cldr.Number.to_string!(12345, locale: "en-IN", currency: "INR", format: "¤#,##,##0.##")
# BUG? I didn't expect to see decimal digits in this case - I need to check the spec
"₹12,345.00"
# Because non-currency formatting with this format does do what I expected:
iex> Cldr.Number.to_string!(12345, locale: "en-IN", format: "#,##,##0.##")
"12,345"
iex> Cldr.Number.to_string!(12345.00, locale: "en-IN", format: "#,##,##0.##")
"12,345"
iex> Cldr.Number.to_string!(12345.67, locale: "en-IN", format: "#,##,##0.##")
"12,345.67"

I'll look into this tonight or tomorrow and see what the spec expects - but it feels like a bug to me.

[petrus-jvrensburg]

Okay thanks, that makes sense.

How would you feel about a PR to ex_money to add a show_decimal_if_zero option to Money.to_string? Then we can look for that flag and force the fractional_digits to zero if the number is an integer, like you did above.

The other Money package (https://hexdocs.pm/money/readme.html) uses a flag named strip_insignificant_fractional_unit to the same effect.

[kipcole9]

I'm fine to add that. Thanks for offering the PR but I'll tackle this one later this evening my time.

[kipcole9]

I've pushed a commit that adds the :no_fraction_if_integer option to Money.to_string/2. Here's the changelog entry. Let me know if this does what you're after?

Enhancements

• Adds an option :no_fraction_if_integer to Money.to_string/2. If truthy this option will set fractional_digits: 0 if money is an integer value. This may be helpful in cases where integer money amounts such as Money.new(:USD, 1234) should be formatted as $1,234 rather than $1,234.00.

[kipcole9]

I'll still work on the bug fix as well and close this issue after that is done.

[petrus-jvrensburg]

That's great, thanks!

[kipcole9]

Bug is fixed. Now when the fractional digits are optional, the format is a currency format and the number is an integer then no fractional digits will be formatted.

iex> Cldr.Number.to_string!(12345, locale: "en-IN", currency: "INR", format: "¤#,##,##0.##")
"₹12,345"

[kipcole9]

Published ex_cldr_numbers version 2.31.3. Closing as completed.