Add wrapper types for all geometries

Project.toml

@@ -12,7 +12,8 @@ julia = "1"
 
 [extras]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+GeoFormatTypes = "68eda718-8dee-11e9-39e7-89f7f65f511f"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "Documenter"]
+test = ["Test", "Documenter", "GeoFormatTypes"]

docs/src/guides/defaults.md

@@ -59,3 +59,50 @@ GeoInterface.y(b) == 2
 c = (;X=1, Y=2, Z=3)
 GeoInterface.z(c) == 3
 ```
+
+# Wrapper types
+
+It is common that a package does not implement all objects supported by
+GeoInterface.jl, and may lack the ability to define features. It is useful
+to define generic objects that can be used in testing and for scripting where
+geometries need to be constructed from components. Using generic wrappers 
+means this is backend agnostic: the same code will work if geometries come from
+GeoJSON.jl, Shapefile.jl, LibGEOS.jl, or other packages defining GeoInterface.jl
+traits.
+
+Wrapper types are provided for constructing geometries out of any lower-level
+components that implement GeoInterface.jl traits. These wrappers can wrap
+objects of the same trait (possibly to add extent data), vectors of child
+objects, or nested vectors of lower level children, such as points.
+
+As an example, we can construct a polygon from any GeoInterface.jl compatible 
+geometries that return `LinearRingTrait` from `GeoInterface.geomtrait`:
+
+```julia
+poly = Polygon([interior, hole1, hole2])
+```
+
+See the API documentation for each wrapper for more details.
+
+- [`Point`](@ref)
+- [`Line`](@ref)
+- [`LineString`](@ref)
+- [`LinearRing`](@ref)
+- [`Polygon`](@ref)
+- [`MultiLineString`](@ref)
+- [`MultiPolygon`](@ref)
+- [`MultiPoint`](@ref)
+- [`PolyhedralSurface`](@ref)
+- [`GeometryCollection`](@ref)
+
+Wrappers for Triangle, Hexagon and some other geometries are yet to be implemented.
+Please make a GitHub issue if you need them.
+
+Feature and FeatureCollection wrappers are also provided, to add properties,
+crs and extents to any GeoInterface.jl compatible geometries.
+
+- [`Feature`](@ref)
+- [`FeatureCollection`](@ref)
+
+Wrappers are not exported by default because they are very common names used by
+other packages. To use them directly, run `using GeoInterface.Wrappers`.

src/GeoInterface.jl

@@ -52,5 +52,9 @@ include("interface.jl")
 include("fallbacks.jl")
 include("utils.jl")
 include("base.jl")
+include("wrappers.jl")
+
+using .Wrappers
+using .Wrappers: geointerface_geomtype
 
 end # module

src/fallbacks.jl

@@ -66,6 +66,7 @@ getpoint(t::AbstractMultiPolygonTrait, geom) = flatten((p for p in getpoint(r))
 npatch(t::AbstractPolyhedralSurfaceTrait, geom)::Integer = ngeom(t, geom)
 getpatch(t::AbstractPolyhedralSurfaceTrait, geom) = getgeom(t, geom)
 getpatch(t::AbstractPolyhedralSurfaceTrait, geom, i::Integer) = getgeom(t, geom, i)
+getpoint(t::AbstractPolyhedralSurfaceTrait, geom) = flatten((p for p in getpoint(g)) for g in getgeom(t, geom))
 
 ## Default iterator
 getgeom(t::AbstractGeometryTrait, geom) = (getgeom(t, geom, i) for i in 1:ngeom(t, geom))
@@ -94,7 +95,7 @@ issimple(t::AbstractMultiPointTrait, geom) = allunique((getgeom(t, geom)))
 issimple(t::AbstractMultiCurveTrait, geom) = all(issimple.(getgeom(t, geom)))
 isclosed(t::AbstractMultiCurveTrait, geom) = all(isclosed.(getgeom(t, geom)))
 
-crs(::AbstractGeometryTrait, geom) = nothing
+crs(::AbstractTrait, geom) = nothing
 
 # FeatureCollection
 getfeature(t::AbstractFeatureCollectionTrait, fc) = (getfeature(t, fc, i) for i in 1:nfeature(t, fc))

src/interface.jl

@@ -408,7 +408,7 @@ getpolygon(geom) = getpolygon(geomtrait(geom), geom)
 Retrieve Coordinate Reference System for given geom.
 In SF this is defined as `SRID`.
 """
-crs(geom) = crs(geomtrait(geom), geom)
+crs(geom) = crs(trait(geom), geom)
 
 """
     extent(obj; fallback=true) -> T <: Extents.Extent