Use reduce to remove points with missing coords

hugovk commented 5 years ago

Thanks for this great site!

I have a GPX from my Strava ZIP that looks like this (I've snipped away most of the track points), where the first <trkpt> has no lon or lat attributes:

<?xml version="1.0" encoding="UTF-8"?>
<gpx xmlns="http://www.topografix.com/GPX/1/1" xmlns:gpxdata="http://www.cluetrust.com/XML/GPXDATA/1/0" creator="Wahoo ELEMNT BOLT" version="5.8">
  <metadata>
    <link href="https://gotoes.org/strava/Combine_GPX_TCX_FIT_Files.php">
      <text>GOTOES STRAVA TOOLS</text>
    </link>
    <time>2019-08-31T09:02:36Z</time>
  </metadata>
  <trk>
    <type>Other</type>
    <trkseg>
      <trkpt>
        <ele>31.2</ele>
        <time>2019-08-31T09:02:36Z</time>
        <extensions>
          <gpxdata:temp>0</gpxdata:temp>
        </extensions>
      </trkpt>
      <trkpt lon="24.93841" lat="60.16992">
        <ele>31.2</ele>
        <time>2019-08-31T09:02:37Z</time>
        <extensions>
          <gpxdata:temp>29</gpxdata:temp>
        </extensions>
      </trkpt>
      <trkpt lon="24.93841" lat="60.16992">
        <ele>31.2</ele>
        <time>2019-08-31T09:02:38Z</time>
        <extensions>
          <gpxdata:temp>29</gpxdata:temp>
        </extensions>
      </trkpt>
    </trkseg>
  </trk>
</gpx>

It fails to load at https://erik.github.io/derive/ and logs this in the console:

ui.js:105 TypeError: Cannot read property 'lat' of undefined
    at track.js:28
    at Array.map (<anonymous>)
    at track.js:27
    at Array.forEach (<anonymous>)
    at track.js:26
    at Array.forEach (<anonymous>)
    at track.js:23
    at track.js:137
    at f.<anonymous> (parser.js:303)
    at f.a.emit (events.js:146)
    at o.onclosetag (parser.js:261)
    at P (sax.js:624)
    at L (sax.js:629)
    at B (sax.js:889)
    at o.write (sax.js:1436)
    at f.parseString (parser.js:322)
    at f.parseString (parser.js:5)
    at track.js:133
    at new Promise (<anonymous>)
    at track.js:132
(anonymous) @ ui.js:105
w @ runtime.js:65
(anonymous) @ runtime.js:303
t.<computed> @ runtime.js:117
S @ image.js:62
a @ image.js:62
Promise.then (async)
S @ image.js:62
s @ image.js:62
(anonymous) @ image.js:62
(anonymous) @ image.js:62
(anonymous) @ ui.js:97
C @ ui.js:110
(anonymous) @ ui.js:356

The error is here: https://github.com/erik/derive/blob/88b9255c795cb7802969e35a1c96aa717d02afcf/src/track.js#L26-L33

It happens because the first track point doesn't have latitude or longitude attributes (see GPX above).

This fix is use reduce instead of map, and discard track points unless they have attributes. (A chained filter and map could be used, but this should have better performance for thousands of points.)

About the data: the problematic file was generated by combining two files using this tool, which is recommended by Strava so will be quite widely used. I don't have the original pre-merge files handy to check if the same issue occurs there or if it was introduced by the merge tool.

I've tested the fix locally with my full Strava archive (1,330 files) and they all load.

hugovk commented 5 years ago

CI failed due to temporary network errors.

It passed on my fork: https://travis-ci.org/hugovk/derive/builds/588418663

hugovk commented 5 years ago

You're welcome, thanks for the dev instructions!

Here's some of the output:

erik / derive

Use reduce to remove points with missing coords #27