kludge to allow hot-plug of optional backends

src/backends.jl

@@ -13,6 +13,26 @@ backends() = _backends
 backend_name() = CURRENT_BACKEND.sym
 _backend_instance(sym::Symbol) = haskey(_backendType, sym) ? _backendType[sym]() : error("Unsupported backend $sym")
 
+# kludge while waiting for Pkg alternatives
+if VERSION >= v"0.7-"
+function _findmod(f::Symbol)
+    for (u,v) in Base.loaded_modules
+        (Symbol(v) == f) && return u
+    end
+    nothing
+end
+function topimport(modname)
+    @eval Base.__toplevel__  import $modname
+    u = _findmod(modname)
+    @eval $modname = Base.loaded_modules[$u]
+end
+else
+    function myimport(modname)
+        @eval import $modname
+    end
+end
+# end kludge
+
 macro init_backend(s)
     str = lowercase(string(s))
     sym = Symbol(str)

src/backends/gr.jl

@@ -67,7 +67,7 @@ end
 
 function _initialize_backend(::GRBackend; kw...)
     @eval begin
-        import GR
+        topimport(:GR)
         export GR
     end
 end

src/backends/hdf5.jl

@@ -142,7 +142,7 @@ end
 
 function _initialize_backend(::HDF5Backend)
     @eval begin
-        import HDF5
+        topimport(:HDF5)
         export HDF5
         if length(HDF5PLOT_MAP_TELEM2STR) < 1
             #Possible element types of high-level data types:

src/backends/inspectdr.jl

@@ -162,7 +162,7 @@ end
 
 function _initialize_backend(::InspectDRBackend; kw...)
     @eval begin
-        import InspectDR
+        topimport(:InspectDR)
         export InspectDR
 
         #Glyph used when plotting "Shape"s:

src/backends/pgfplots.jl

@@ -58,7 +58,7 @@ end
 
 function _initialize_backend(::PGFPlotsBackend; kw...)
     @eval begin
-        import PGFPlots
+        topimport(:PGFPlots)
         export PGFPlots
     end
 end

src/backends/plotlyjs.jl

@@ -29,7 +29,7 @@ end
 
 function _initialize_backend(::PlotlyJSBackend; kw...)
     @eval begin
-        import PlotlyJS
+        topimport(:PlotlyJS)
         export PlotlyJS
     end
 

src/backends/pyplot.jl

@@ -77,8 +77,12 @@ function _initialize_backend(::PyPlotBackend)
         # problem: https://github.com/tbreloff/Plots.jl/issues/308
         # solution: hack from @stevengj: https://github.com/stevengj/PyPlot.jl/pull/223#issuecomment-229747768
         otherdisplays = splice!(Base.Multimedia.displays, 2:length(Base.Multimedia.displays))
-        import PyPlot, PyCall
-        import LaTeXStrings: latexstring
+
+        topimport(:PyPlot)
+        topimport(:PyCall)
+        topimport(:LaTeXStrings)
+        latexstring = LaTeXStrings.latexstring
+
         append!(Base.Multimedia.displays, otherdisplays)
 
         export PyPlot

src/backends/template.jl

@@ -5,7 +5,7 @@
 
 function _initialize_backend(::[PkgName]Backend; kw...)
     @eval begin
-        import [PkgName]
+        topimport(:[PkgName])
         export [PkgName]
         # todo: other initialization that needs to be eval-ed
     end

src/backends/unicodeplots.jl

@@ -42,7 +42,7 @@ end
 
 function _initialize_backend(::UnicodePlotsBackend; kw...)
     @eval begin
-        import UnicodePlots
+        topimport(:UnicodePlots)
         export UnicodePlots
     end
 end