Improve validation error messages relating to even/odd number of arguments

[anandthakker]

When case, match, interpolate, and step don't get the right number of arguments, they produce validation errors that just say "expected odd [or even] number of arguments." We should clarify these to say something more helpful. This will probably require that we don't simply do a preflight check on the number of arguments, which means we'd have a little more wasted parsing work in the case of a validation error, but I think that's worth it.

[mmainzer]

Has there been any movement on this?

I'm trying to replicate the gl js example here: https://docs.mapbox.com/mapbox-gl-js/example/data-join/ with my own local data:

var expression = ["match", ["get", "Area"]];

// Calculate color for each state based on the unemployment rate
data.forEach(function(row) {
	var green = (row["2028 Jobs"] / maxValue) * 255;
	var color = "rgba(" + 0 + ", " + green + ", " + 0 + ", 1)";
	expression.push(row["Area"], color);
});

// Add layer from the vector tile source with data-driven style
map.addLayer({
	"id": "zips-join",
	"type": "fill",
	"source": "zip-codes",
	"source-layer": "zip-codes",
	"paint": {
		"fill-color": expression
	}
}, 'waterway-label');

However I get the following error: layers.zips-join.paint.fill-color: Expected an even number of arguments.

Not sure where to even begin

[eballeste]

stumbled across this issue #8446, the error was unintuitive because it wasn't as obvious that the zoom is an actual input and should be treated as the first argument to the step expression...

[bhison]

Has there been any movement on this?

I'm trying to replicate the gl js example here: https://docs.mapbox.com/mapbox-gl-js/example/data-join/ with my own local data:

var expression = ["match", ["get", "Area"]];

// Calculate color for each state based on the unemployment rate
data.forEach(function(row) {
	var green = (row["2028 Jobs"] / maxValue) * 255;
	var color = "rgba(" + 0 + ", " + green + ", " + 0 + ", 1)";
	expression.push(row["Area"], color);
});

// Add layer from the vector tile source with data-driven style
map.addLayer({
	"id": "zips-join",
	"type": "fill",
	"source": "zip-codes",
	"source-layer": "zip-codes",
	"paint": {
		"fill-color": expression
	}
}, 'waterway-label');

However I get the following error: layers.zips-join.paint.fill-color: Expected an even number of arguments.

Not sure where to even begin

I assume you've moved on by now, but for the benefit of others coming across this, you may solve the issue by adding a final value of "" to your expression array, representing a default value.

[domlet]

I'm removing the docs label here and leaving this issue to be addressed in #9485