discrepancy between code and documentation for union

[andrewharvey]

The JSDoc for turn.union at https://github.com/Turfjs/turf/blob/master/packages/turf-union/index.ts says:

• Takes two {@link (Multi)Polygon(s)} and returns a combined polygon. If the input polygons are not contiguous, this function returns a {@link MultiPolygon} feature.

However the online documentation at http://turfjs.org/docs/#union says:

Takes two or more polygons

which is wrong, as union only takes two polygons, as two arguments, not any number of polygons as the live documentation suggests.

I'm not sure where I need to place the PR to fix this, given it's already fixed in master.

[lostpebble]

I've been making use of union recently and passing in multiple polygons like so:

const newGeometryFeature = union(...geometryFeatures);

It seems to be combining more than two polygon features together. But looking at the code in master, it seems like it only takes two? Kinda weird... Does the master code and released version not align?

I'm using "@turf/turf": "5.1.6".

[andrewharvey]

const newGeometryFeature = union(...geometryFeatures);

That's what I tried the first time because of the documentation, but it failed, confused why I diged into the source code to find that it only takes two feature arguments. Instead I had use union inside an Array.reduce function to get the same affect.

It seems to be combining more than two polygon features together. But looking at the code in master, it seems like it only takes two? Kinda weird... Does the master code and released version not align?

Yeah that's what I'm very confused about too!

[rowanwins]

Hi @andrewharvey & @lostpebble

Sorry for the confusion. Some of those docs are probably reflectively of the change from JSTS which was used in v5 and earlier which took any number of arguments. In v6 martinez was used which only takes 2 arguments.

In v7 I've implemented polygon-clipping which goes back to taking any number of arguments. The latest hasn't been published yet as a turf module yet but the 0.14.0 release of polygon-clipping looks really good and passes all the turf tests.

[brylie]

This almost seems like a regression. Is there a way to get a union of a MultiPolygon with Turf.js?

[rowanwins]

Docs and code are now in sync. It's still on my radar to relook at adding support for more than 2 polys.