Fix get call; recommend juliarc file

README.md

@@ -7,6 +7,11 @@ These functions were formerly a part of Base Julia.
 Users with a build of Julia based on Intel's Math Kernel Library (MKL) can take use MKL
 for FFTs by setting an environment variable `JULIA_FFTW_PROVIDER` to `MKL` and running
 `Pkg.build("FFTW")`.
+To ensure that you always get MKL FFTs, it's recommended that you put
+```julia
+ENV["JULIA_FFTW_PROVIDER"] = "MKL"
+```
+in your .juliarc.jl file.
 Note however that MKL provides only a subset of the functionality provided by FFTW. See
 Intel's [documentation](https://software.intel.com/en-us/mkl-developer-reference-c-using-fftw3-wrappers)
 for more information about potential differences or gaps in functionality.

deps/build.jl

@@ -1,7 +1,7 @@
 # If BLAS was compiled with MKL and the user wants MKL-based FFTs, we'll oblige.
 # In that case, we have to do this little dance to get around having to use BinDeps
 # for a library that's already linked to Julia.
-if get(ENV, "JULIA_FFTW_PROVIDER") == "MKL" && Base.BLAS.vendor() === :mkl
+if get(ENV, "JULIA_FFTW_PROVIDER", "") == "MKL" && Base.BLAS.vendor() === :mkl
     mklpath = Libdl.dlpath("libmkl_rt")
     depsfile = joinpath(@__DIR__, "deps.jl")
     isfile(depsfile) && rm(depsfile, force=true)

docs/src/index.md

@@ -17,6 +17,11 @@ from the Julia REPL.
 Users with a build of Julia based on Intel's Math Kernel Library (MKL) can take use MKL
 for FFTs by setting an environment variable `JULIA_FFTW_PROVIDER` to `MKL` and running
 `Pkg.build("FFTW")`.
+To ensure that you always get MKL FFTs, it's recommended that you put
+```julia
+ENV["JULIA_FFTW_PROVIDER"] = "MKL"
+```
+in your .juliarc.jl file.
 Note however that MKL provides only a subset of the functionality provided by FFTW. See
 Intel's [documentation](https://software.intel.com/en-us/mkl-developer-reference-c-using-fftw3-wrappers)
 for more information about potential differences or gaps in functionality.