Workout name in activity fit file is an array of strings instead of a single string

6915698 4 days ago

When parsing an activity fit file recorded with my forerunner255, I received an array of strings for the workout name. Per the documentation, it should be a single string.

raw_messages['workout_mesgs'][0]['wkt_name'] = ['SL 5x5 A', '', 'iceps with COOLDOWN']

It looks like some stale data is being returned.

I also see this problem with other fields.

raw_messages['exercise_title_mesgs'][2]['wkt_step_name'] = ['Barbell Back Squat', '', '', 'Pool Swim', '', 'U\x01<', '', 'e\n\x14Sna\x1dsho\x05', '', '', '', '', '\x1c', '\x06']

0 Ben FIT 4 days ago

This is a common issue with all string fields. This has to do with the device allocating a fixed amount of memory for a string and not always initializing all the bytes to zero. The decoders split string fields by the null terminator and if there are any uninitialized bytes written to the file then the field may end up with as as array of strings.

You don't notice this when using some of the SDKs since the getters always returns the value at index zero
https://github.com/garmin/fit-java-sdk/blob/main/src/main/com/garmin/fit/WorkoutMesg.java#L151

and the setters always store the value at index 0
https://github.com/garmin/fit-java-sdk/blob/main/src/main/com/garmin/fit/WorkoutMesg.java#L160

But with the Python and JavaScript SDKs, since there are not getters or setter you will see the array.

With the JavaScript array you can do something like this, there is something similar for Python too.

const str = Array.isArray(mesg.field) ? mesg.field[0] : mesg.field;

The binary protocol actually allows any field to be an array. The profile is only enforced at the getter/setter level and not in the actual encoding or decoding.

We have it in our backlog to add an isArray property to the field definitions in the profile, but there are not a lot of string fields in the SDK so it has not been a high priority.
https://github.com/garmin/fit-javascript-sdk/blob/main/src/profile.js