Load CondaPkg lazily, and drop Pkg as a dependency

Author: JamesWrigley

Project.toml

@@ -9,7 +9,6 @@ Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
 MacroTools = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
-Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Preferences = "21216c6a-2e73-6563-6e65-726566657250"
 Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
@@ -22,7 +21,6 @@ Dates = "1"
 Libdl = "1"
 MacroTools = "0.5"
 Markdown = "1"
-Pkg = "1"
 Preferences = "1"
 PyCall = "1"
 Serialization = "1"

docs/src/pythoncall.md

@@ -282,7 +282,8 @@ to your current Julia project containing Python and any required Python packages
 
 You can configure PythonCall with the preferences listed below. These can be set either as
 [Julia preferences](https://github.com/JuliaPackaging/Preferences.jl) or as environment
-variables.
+variables. If an environment variable and preference are both set, the
+preference will take priority.
 
 | Preference | Environment Variable | Description |
 | ---------- | -------------------- | ----------- |

src/C/C.jl

@@ -9,11 +9,13 @@ using ..Utils
 
 using Base: @kwdef
 using UnsafePointers: UnsafePtr
-using CondaPkg: CondaPkg
-using Pkg: Pkg
 using Libdl:
     dlpath, dlopen, dlopen_e, dlclose, dlsym, dlsym_e, RTLD_LAZY, RTLD_DEEPBIND, RTLD_GLOBAL
 
+if Utils.getpref_exe(; prefonly=true) == "@CondaPkg"
+    using CondaPkg: CondaPkg
+end
+
 import ..PythonCall:
     python_executable_path, python_library_path, python_library_handle, python_version
 

src/C/context.jl

@@ -124,7 +124,7 @@ function init_context()
     else
         # Find Python executable
         exe_path = Utils.getpref_exe()
-        if exe_path == "" || exe_path == "@CondaPkg"
+        if exe_path == "@CondaPkg"
             if CondaPkg.backend() == :Null
                 exe_path = Sys.which("python")
                 if exe_path === nothing

src/JlWrap/JlWrap.jl

@@ -30,7 +30,6 @@ import ..PythonCall:
     PyObjectMatrix,
     PyObjectArray
 
-using Pkg: Pkg
 using Base: @propagate_inbounds, allocatedinline
 
 import ..Core: Py
@@ -70,7 +69,6 @@ function __init__()
     jl.Core = Base.Core
     jl.Base = Base
     jl.Main = Main
-    jl.Pkg = Pkg
     jl.PythonCall = PythonCall
 end
 

src/Utils/Utils.jl

@@ -2,19 +2,23 @@ module Utils
 
 using Preferences: @load_preference
 
-function getpref(::Type{T}, prefname, envname, default = nothing) where {T}
+function getpref(::Type{T}, prefname, envname, default = nothing; prefonly=false) where {T}
     ans = @load_preference(prefname, nothing)
     ans === nothing || return checkpref(T, ans)::T
-    ans = get(ENV, envname, "")
-    isempty(ans) || return checkpref(T, ans)::T
+
+    if !prefonly
+        ans = get(ENV, envname, "")
+        isempty(ans) || return checkpref(T, ans)::T
+    end
+
     return default
 end
 
 checkpref(::Type{String}, x) = error("invalid preference of type $(type(x)), expecting a string")
 checkpref(::Type{String}, x::AbstractString) = convert(String, x)
 
 # Specific preference functions
-getpref_exe() = getpref(String, "exe", "JULIA_PYTHONCALL_EXE", "")
+getpref_exe(; kwargs...) = getpref(String, "exe", "JULIA_PYTHONCALL_EXE", "@CondaPkg"; kwargs...)
 getpref_lib() = getpref(String, "lib", "JULIA_PYTHONCALL_LIB", nothing)
 getpref_pickle() = getpref(String, "pickle", "JULIA_PYTHONCALL_PICKLE", "pickle")