feat: add @temp to the DEFAULT_LOAD_PATH

Author: ven-k

base/initdefs.jl

@@ -122,6 +122,7 @@ end
 # entries starting with `@` are named environments:
 #  - the first three `#`s in a named environment are replaced with version numbers
 #  - `@stdlib` is a special name for the standard library and expands to its path
+#  - `@temp` expands to a temporary directory path
 
 # if you want a current env setup, use direnv and
 # have your .envrc do something like this:
@@ -131,21 +132,23 @@ end
 # this will inherit an existing JULIA_LOAD_PATH value or if there is none, leave
 # a trailing empty entry in JULIA_LOAD_PATH which will be replaced with defaults.
 
-const DEFAULT_LOAD_PATH = ["@", "@v#.#", "@stdlib"]
+const DEFAULT_LOAD_PATH = ["@", "@temp", "@v#.#", "@stdlib"]
 
 """
     LOAD_PATH
 
 An array of paths for `using` and `import` statements to consider as project
 environments or package directories when loading code. It is populated based on
 the [`JULIA_LOAD_PATH`](@ref JULIA_LOAD_PATH) environment variable if set;
-otherwise it defaults to `["@", "@v#.#", "@stdlib"]`. Entries starting with `@`
+otherwise it defaults to `["@", "@temp", "@v#.#", "@stdlib"]`. Entries starting with `@`
 have special meanings:
 
 - `@` refers to the "current active environment", the initial value of which is
   initially determined by the [`JULIA_PROJECT`](@ref JULIA_PROJECT) environment
   variable or the `--project` command-line option.
 
+- `@temp` expands to a temporary directory.
+
 - `@stdlib` expands to the absolute path of the current Julia installation's
   standard library directory.
 

test/loading.jl

@@ -683,7 +683,7 @@ end
 
 # Base.active_project when version directory exist in depot, but contains no project file
 mktempdir() do dir
-    vdir = Base.DEFAULT_LOAD_PATH[2]
+    vdir = Base.DEFAULT_LOAD_PATH[3]
     vdir = replace(vdir, "#" => VERSION.major, count = 1)
     vdir = replace(vdir, "#" => VERSION.minor, count = 1)
     vdir = replace(vdir, "#" => VERSION.patch, count = 1)
@@ -699,6 +699,10 @@ mktempdir() do dir
     @test success(cmd)
 end
 
+@testset "`@temp` in `DEFAULT_LOAD_PATH`" begin
+    @test tempdir() == Base.load_path_expand(Base.DEFAULT_LOAD_PATH[2])[1:lastindex(tempdir())]
+end
+
 @testset "expansion of JULIA_LOAD_PATH" begin
     s = Sys.iswindows() ? ';' : ':'
     tmp = "/this/does/not/exist"