Move work to compile time

Previously, we were loading preferences within `__init__()`; move it out
to top-level statements so that the preferences are loaded at compile
time and baked into the `.ji` files.

Author: staticfloat

src/products/executable_generators.jl

@@ -49,22 +49,27 @@ function declare_new_executable_product(product_name)
 end
 
 macro declare_executable_product(product_name)
+    path_name = string(product_name, "_path")
     return excat(
         # We will continue to support `withenv`-style for as long as we must
         declare_old_executable_product(product_name),
         # We will, however, urge users to move to the thread-safe `addenv`-style on Julia 1.6+
         declare_new_executable_product(product_name),
+        # Perform a compile-time load of a path preference override
+        :($(Symbol(path_name)) = $(emit_preference_path_load(path_name))),
     )
 end
 
 macro init_executable_product(product_name, product_path)
-    preference_name = string(product_name, "_path")
-    path_name = Symbol(preference_name)
+    path_name = Symbol(string(product_name, "_path"))
     return esc(quote
+        global $(path_name)
         # Locate the executable on-disk, store into $(path_name)
-        global $(path_name) = $(emit_preference_path_load(preference_name, product_path))
+        if $(path_name) === nothing
+            $(path_name) = joinpath(artifact_dir, $(product_path))
+        end
 
         # Add this executable's directory onto the list of PATH's that we'll need to expose to dependents
-        push!(PATH_list, joinpath(artifact_dir, $(dirname(product_path))))
+        push!(PATH_list, dirname($(path_name)))
     end)
 end

src/products/file_generators.jl

@@ -3,7 +3,7 @@ macro declare_file_product(product_name)
     path_name = Symbol(string(product_name, "_path"))
     return esc(quote
         # These will be filled in by init_file_product().
-        $(path_name) = ""
+        $(path_name) = $(emit_preference_path_load(string(product_name, "_path")))
         $(product_name) = ""
         function $(get_path_name)()
             return $(path_name)::String
@@ -12,11 +12,13 @@ macro declare_file_product(product_name)
 end
 
 macro init_file_product(product_name, product_path)
-    preference_name = string(product_name, "_path")
-    path_name = Symbol(preference_name)
+    path_name = Symbol(string(product_name, "_path"))
     return esc(quote
+        global $(path_name)
         # FileProducts are very simple, and we maintain the `_path` suffix version for consistency
-        global $(path_name) = $(emit_preference_path_load(preference_name, product_path))
+        if $(path_name) === nothing
+            $(path_name) = joinpath(artifact_dir, $(product_path))
+        end
         global $(product_name) = $(path_name)
     end)
 end

src/products/library_generators.jl

@@ -18,7 +18,7 @@ macro declare_library_product(product_name, product_soname)
         quote
             # These will be filled in by init_library_product()
             $(handle_name) = C_NULL
-            $(path_name) = ""
+            $(path_name) = $(emit_preference_path_load(string(product_name, "_path")))
             function $(get_path_name)()
                 return $(path_name)::String
             end
@@ -43,7 +43,10 @@ macro init_library_product(product_name, product_path, dlopen_flags)
     preference_name = string(product_name, "_path")
     path_name = Symbol(preference_name)
     return excat(quote
-            global $(path_name) = $(emit_preference_path_load(preference_name, product_path))
+            global $(path_name)
+            if $(path_name) === nothing
+                $(path_name) = joinpath(artifact_dir, $(product_path))
+            end
             # Manually `dlopen()` this right now so that future invocations
             # of `ccall` with its path/SONAME will find this path immediately.
             # dlopen_flags === nothing means to not dlopen the library.

src/wrapper_generators.jl

@@ -55,17 +55,17 @@ end
     emit_preference_path_load(pref_name, default_value)
 
 On Julia 1.6+, emits a `load_preference()` call for the given preference name,
-with the given default value.  On Julia 1.5-, simply emits the default value.
+returning `nothing` if it is not loaded.  On Julia v1.5-, always returns `nothing`.
 """
-function emit_preference_path_load(pref_name, product_path)
+function emit_preference_path_load(pref_name)
     # Can't use `Preferences.jl` on older Julias, just always use the default value in that case
     @static if VERSION < v"1.6.0-DEV"
         return quote
-            joinpath(artifact_dir, $(product_path))
+            nothing
         end
     else
         return quote
-            @load_preference($(pref_name), joinpath(artifact_dir, $(product_path)))
+            @load_preference($(pref_name), nothing)
         end
     end
 end