Option -relax- and un-insheet-able field names

[matthew-white]

Option relax specifies that the do-file ignore fields in the form that are not in the data; by default, it results in an error. However, it still results in an error for nonexistent fields with problematic (uninsheetable) field names, e.g., those whose Stata names are a duplicate with another field's. Currently option relax writes code to attach char metadata as follows:

local pos : list posof "field_name" in fields
local var : word `pos' of `all'
capture confirm variable `var', exact
if _rc ///
    local formnotdata `formnotdata' `var'
else {
    char commands...
}

Yet if `pos' == 0, :word results in an error:

. local var : word `pos' of `all'
invalid syntax
r(198);

Thus, the code should look more like:

local pos : list posof "field_name" in fields
if !`pos' ///
    local found 0
else {
    local var : word `pos' of `all'
    capture confirm variable `var', exact
    local found = !_rc
}
if !`found' ///
    local formnotdata `formnotdata' `var'
else {
    char commands...
}

The following also works. It's slightly less clean, as it adds an extra capture, but it's fine as a way to facilitate an easier find/replace for those wanting an immediate fix.

local pos : list posof "field_name" in fields
capture local var : word `pos' of `all'
if !_rc ///
    capture confirm variable `var', exact
if _rc ///
    local formnotdata `formnotdata' `var'
else {
    char commands...
}

On a final note, we shouldn't add `var' to `formnotdata' but rather the field name.

[matthew-white]

I think we may simply remove option relax in a future version, as it makes the code more complex and adds maintenance costs, and it shouldn't be needed when the submission data is compatible with the ODK Briefcase format (see #46).