add implementation of shapecoords for AbstractGeometry

this is for packages implementing GeoInterface at the level of
AbstractGeometry, rather than the subtypes
AbstractPoint…AbstractMultiPolygon. They just need to define
`geotype(::AbstractGeometry)` in order for this package to identify
which geometry type it is, and return the corresponding coordinates.

We first define methods (`pointcoords()`,…,`multipolygoncoords()`) on
AbstractGeometry that returns the coordinates for different geometry
types. We can then have a `shapecoords(geom::AbstractGeometry)` that
uses `geotype(geom)` to look up the corresponding method to call

src/plotrecipes.jl

@@ -1,86 +1,145 @@
-shapecoords(geom::AbstractPoint) = [tuple(coordinates(geom)...)]
+function pointcoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :Point
+    [tuple(coordinates(geom)...)]
+end
+
+function multipointcoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :MultiPoint
+    coords = coordinates(geom)
+    first.(coords), last.(coords)
+end
+
+function linestringcoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :LineString
+    coords = coordinates(geom)
+    first.(coords), last.(coords)
+end
+
+function multilinestringcoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :MultiLineString
+    x, y = Float64[], Float64[]
+    for line in coordinates(geom)
+        append!(x, first.(line)); push!(x, NaN)
+        append!(y, last.(line)); push!(y, NaN)
+    end
+    x, y
+end
+
+function polygoncoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :Polygon
+    ring = first(coordinates(geom)) # currently doesn't plot holes
+    first.(ring), last.(ring)
+end
+
+function multipolygoncoords(geom::AbstractGeometry)
+    @assert geotype(geom) == :MultiPolygon
+    x, y = Float64[], Float64[]
+    for poly in coordinates(geom)
+        ring = first(coordinates(poly)) # currently doesn't plot holes
+        append!(x, first.(ring)); push!(x, NaN)
+        append!(y, last.(ring)); push!(y, NaN)
+    end
+    x, y
+end
+
+shapecoords(geom::AbstractPoint) = pointcoords(geom)
+shapecoords(geom::AbstractMultiPoint) = multipointcoords(geom)
+shapecoords(geom::AbstractLineString) = linestringcoords(geom)
+shapecoords(geom::AbstractMultiLineString) = multilinestringcoords(geom)
+shapecoords(geom::AbstractPolygon) = polygoncoords(geom)
+shapecoords(geom::AbstractMultiPolygon) = multipolygoncoords(geom)
+
+function shapecoords(geom::AbstractGeometry)
+    gtype = geotype(geom)
+    if gtype == :Point
+        return pointcoords(geom)
+    elseif gtype == :MultiPoint
+        return multipointcoords(geom)
+    elseif gtype == :LineString
+        return linestringcoords(geom)
+    elseif gtype == :MultiLineString
+        return multilinestringcoords(geom)
+    elseif gtype == :Polygon
+        return polygoncoords(geom)
+    elseif gtype == :MultiPolygon
+        return multipolygoncoords(geom)
+    else
+        warn("unknown geometry type: $gtype")
+    end
+end
+
 RecipesBase.@recipe f(geom::AbstractPoint) = (
     aspect_ratio := 1;
     seriestype --> :scatter;
     legend --> :false;
     shapecoords(geom)
 )
 
-function shapecoords(geom::AbstractMultiPoint)
-    coords = coordinates(geom)
-    first.(coords), last.(coords)
-end
 RecipesBase.@recipe f(geom::AbstractMultiPoint) = (
     aspect_ratio := 1;
     seriestype --> :scatter;
     legend --> :false;
     shapecoords(geom)
 )
 
-function shapecoords(geom::AbstractLineString)
-    coords = coordinates(geom)
-    first.(coords), last.(coords)
-end
 RecipesBase.@recipe f(geom::AbstractLineString) = (
     aspect_ratio := 1;
     seriestype --> :path;
     legend --> :false;
     shapecoords(geom)
 )
 
-function shapecoords(geom::AbstractMultiLineString)
-    x, y = Float64[], Float64[]
-    for line in coordinates(geom)
-        append!(x, first.(line)); push!(x, NaN)
-        append!(y, last.(line)); push!(y, NaN)
-    end
-    x, y
-end
 RecipesBase.@recipe f(geom::AbstractMultiLineString) = (
     aspect_ratio := 1;
     seriestype --> :path;
     legend --> :false;
     shapecoords(geom)
 )
 
-function shapecoords(geom::AbstractPolygon)
-    ring = first(coordinates(geom)) # currently doesn't plot holes
-    first.(ring), last.(ring)
-end
 RecipesBase.@recipe f(geom::AbstractPolygon) = (
     aspect_ratio := 1;
     seriestype --> :shape;
     legend --> :false;
     shapecoords(geom)
 )
 
-function shapecoords(geom::AbstractMultiPolygon)
-    x, y = Float64[], Float64[]
-    for poly in coordinates(geom)
-        ring = first(coordinates(poly)) # currently doesn't plot holes
-        append!(x, first.(ring)); push!(x, NaN)
-        append!(y, last.(ring)); push!(y, NaN)
-    end
-    x, y
-end
 RecipesBase.@recipe f(geom::AbstractMultiPolygon) = (
     aspect_ratio := 1;
     seriestype --> :shape;
     legend --> :false;
     shapecoords(geom)
 )
 
+RecipesBase.@recipe function f(geom::AbstractGeometry)
+    aspect_ratio := 1
+    legend --> :false
+    gtype = geotype(geom)
+    if gtype == :Point || gtype == :MultiPoint
+        seriestype := :scatter
+    elseif gtype == :LineString || gtype == :MultiLineString
+        seriestype := :path
+    elseif gtype == :Polygon || gtype == :MultiPolygon
+        seriestype := :shape
+    else
+        warn("unknown geometry type: $gtype")
+    end
+    shapecoords(geom)
+end
+
 RecipesBase.@recipe function f(geom::Vector{<:AbstractGeometry})
     aspect_ratio := 1
     legend --> :false
     for g in geom
         @series begin
-            if g isa AbstractPoint || g isa AbstractMultiPoint
+            gtype = geotype(g)
+            if gtype == :Point || gtype == :MultiPoint
                 seriestype := :scatter
-            elseif g isa AbstractLineString || g isa AbstractMultiLineString
+            elseif gtype == :LineString || gtype == :MultiLineString
                 seriestype := :path
-            elseif g isa AbstractPolygon || g isa AbstractMultiPolygon
+            elseif gtype == :Polygon || gtype == :MultiPolygon
                 seriestype := :shape
+            else
+                warn("unknown geometry type: $gtype")
             end
             shapecoords(g)
         end