Fix bug in ply_type_name() for empty list properties

Author: Chris Foster

src/io.jl

@@ -44,7 +44,12 @@ ply_type_name(::Int64)    = "int64"
 ply_type_name(::Float32)  = "float32"
 ply_type_name(::Float64)  = "float64"
 
-ply_type_name(A::AbstractArray)  = ply_type_name(A[1])
+typealias PlyNativeType Union{UInt8,UInt16,UInt32,UInt64,Int8,Int16,Int32,Int64,Float32,Float64}
+
+ply_type_name{T<:PlyNativeType}(A::AbstractArray{T}) = ply_type_name(T)
+
+ply_type_name(A::AbstractArray) = !isempty(A) ? ply_type_name(A[1]) :
+                                  error("Unknown ply element type name for empty array of type $(typeof(A))")
 
 
 const _host_is_little_endian = (ENDIAN_BOM == 0x04030201)

test/runtests.jl

@@ -21,7 +21,7 @@ using Base.Test
     push!(ply, PlyComment("Final comment"))
 
     buf = IOBuffer()
-    save_ply(ply, buf, ascii=true, )
+    save_ply(ply, buf, ascii=true)
     str = takebuf_string(buf)
     open("simple_test_tmp.ply", "w") do fid
         write(fid, str)
@@ -50,6 +50,32 @@ using Base.Test
     """
 end
 
+@testset "empty elements" begin
+    ply = Ply()
+
+    push!(ply, PlyElement("A", ArrayProperty("x", UInt8[])))
+    push!(ply, PlyElement("B", ListProperty("a_list", Vector{Int64}[[], [], []])))
+
+    buf = IOBuffer()
+    save_ply(ply, buf, ascii=true)
+    str = takebuf_string(buf)
+    open("empty_test_tmp.ply", "w") do fid
+        write(fid, str)
+    end
+    @test str ==
+    """
+    ply
+    format ascii 1.0
+    element A 0
+    property uint8 x
+    element B 3
+    property list int32 int64 a_list
+    end_header
+    0 
+    0 
+    0 
+    """
+end
 
 @testset "roundtrip" begin
     @testset "ascii=$test_ascii" for test_ascii in [false, true]