Missing value support for integers in SPSS

[gorcha]

Another one from haven! 🙂
From tidyverse/haven#596.

Currently missing value support for SPSS is limited to doubles and strings because of an explicit type check in the functions that write out the missing values info:

ReadStat/src/spss/readstat_sav_write.c

Lines 244 to 259 in a8e6705

	static readstat_error_t sav_n_missing_values(int *out_n_missing_values, readstat_variable_t *r_variable) {
	int n_missing_values = 0;
	if (r_variable->type == READSTAT_TYPE_DOUBLE) {
	n_missing_values = sav_n_missing_double_values(r_variable);
	} else if (readstat_variable_get_storage_width(r_variable) <= 8) {
	n_missing_values = sav_n_missing_string_values(r_variable);
	}
	if (abs(n_missing_values) > 3) {
	return READSTAT_ERROR_TOO_MANY_MISSING_VALUE_DEFINITIONS;
	}
	if (out_n_missing_values)
	*out_n_missing_values = n_missing_values;
	return READSTAT_OK;
	}

ReadStat/src/spss/readstat_sav_write.c

Lines 346 to 353 in a8e6705

	static readstat_error_t sav_emit_variable_missing_values(readstat_writer_t *writer, readstat_variable_t *r_variable) {
	if (r_variable->type == READSTAT_TYPE_DOUBLE) {
	return sav_emit_variable_missing_double_values(writer, r_variable);
	} else if (readstat_variable_get_storage_width(r_variable) <= 8) {
	return sav_emit_variable_missing_string_values(writer, r_variable);
	}
	return READSTAT_OK;
	}

It seems like it should be OK to just use the double methods for all non-string values (since integers and 32 bit floats are all converted to doubles in SPSS output anyway) - it probably just needs a change to the conditional logic in these functions and maybe a couple of additional readstat_add_missing_* functions in here to deal with other types:
https://github.com/WizardMac/ReadStat/blob/a8e6705453f0e610a698a4d98b3dfa3087cf4b28/src/readstat_variable.c

I can chuck together a PR if you're happy with this approach?

[evanmiller]

From your perspective, would it be sufficient to change the type checks to:

if (readstat_variable_get_type_class(r_variable) == READSTAT_TYPE_CLASS_NUMERIC)

?

[gorcha]

Yep that's perfect, thank you!

[evanmiller]

Please try the latest dev commits and let me know if that works for you.

[gorcha]

That works perfectly, thanks again