Fix #38491: fix an abspath() edge case on Windows (#38981)

* Fix #38491: fix an abspath() edge case on Windows

* Update base/path.jl

Co-authored-by: Jameson Nash <vtjnash@gmail.com>

* Update base/path.jl

* Update test/path.jl

Co-authored-by: Jameson Nash <vtjnash@gmail.com>

Co-authored-by: Mustafa M <mus-m@outlook.com>
Co-authored-by: Jameson Nash <vtjnash@gmail.com>
(cherry picked from commit f023677)

base/path.jl

@@ -387,7 +387,19 @@ normpath(a::AbstractString, b::AbstractString...) = normpath(joinpath(a,b...))
 Convert a path to an absolute path by adding the current directory if necessary.
 Also normalizes the path as in [`normpath`](@ref).
 """
-abspath(a::String) = normpath(isabspath(a) ? a : joinpath(pwd(),a))
+function abspath(a::String)::String
+    if !isabspath(a)
+        cwd = pwd()
+        a_drive, a_nodrive = splitdrive(a)
+        if a_drive != "" && lowercase(splitdrive(cwd)[1]) != lowercase(a_drive)
+            cwd = a_drive * path_separator
+            a = joinpath(cwd, a_nodrive)
+        else
+            a = joinpath(cwd, a)
+        end
+    end
+    return normpath(a)
+end
 
 """
     abspath(path::AbstractString, paths::AbstractString...) -> String

test/path.jl

@@ -9,6 +9,23 @@
         @test isabspath(S(homedir()))
         @test !isabspath(S("foo"))
     end
+    if Sys.iswindows()
+        @testset "issue #38491" begin
+            pwd_drive = uppercase(splitdrive(pwd())[1])
+            drive = (pwd_drive == "X:") ? "Y:" : "X:"
+            @test abspath("$(lowercase(drive))a\\b\\c") == "$(lowercase(drive))\\a\\b\\c"
+            @test abspath("$(uppercase(drive))a\\b\\c") == "$(uppercase(drive))\\a\\b\\c"
+            @test abspath("$(lowercase(drive))a") == "$(lowercase(drive))\\a"
+            @test abspath("$(uppercase(drive))a") == "$(uppercase(drive))\\a"
+            @test abspath(lowercase(drive)) == "$(lowercase(drive))\\"
+            @test abspath(uppercase(drive)) == "$(uppercase(drive))\\"
+
+            @test lowercase(abspath("$(pwd_drive)a\\b\\c")) == lowercase(joinpath(pwd(), "a\\b\\c"))
+            @test lowercase(abspath("$(pwd_drive)a")) == lowercase(joinpath(pwd(), "a"))
+            @test lowercase(abspath(lowercase(pwd_drive))) == lowercase("$(pwd())\\")
+            @test lowercase(abspath(uppercase(pwd_drive))) == lowercase("$(pwd())\\")
+        end
+    end
     @test basename(S("foo$(sep)bar")) == "bar"
     @test dirname(S("foo$(sep)bar")) == "foo"