allow -m to run the entry point in a submodule (#55265)

Author: KristofferC

base/client.jl

@@ -292,12 +292,12 @@ function exec_options(opts)
             invokelatest(show, Core.eval(Main, parse_input_line(arg)))
             println()
         elseif cmd == 'm'
-            @eval Main import $(Symbol(arg)).main
+            entrypoint = push!(split(arg, "."), "main")
+            Base.eval(Main, Expr(:import, Expr(:., Symbol.(entrypoint)...)))
             if !should_use_main_entrypoint()
                 error("`main` in `$arg` not declared as entry point (use `@main` to do so)")
             end
             return false
-
         elseif cmd == 'L'
             # load file immediately on all processors
             if !distributed_mode

test/loading.jl

@@ -1584,6 +1584,7 @@ end
 @testset "-m" begin
     rot13proj = joinpath(@__DIR__, "project", "Rot13")
     @test readchomp(`$(Base.julia_cmd()) --startup-file=no --project=$rot13proj -m Rot13 --project nowhere ABJURER`) == "--cebwrpg abjurer NOWHERE "
+    @test readchomp(`$(Base.julia_cmd()) --startup-file=no --project=$rot13proj -m Rot13.Rot26 --project nowhere ABJURER`) == "--project nowhere ABJURER "
 end
 
 @testset "workspace loading" begin

test/project/Rot13/src/Rot13.jl

@@ -12,4 +12,17 @@ function (@main)(args)
     return 0
 end
 
+module Rot26 # LOL
+
+import ..rot13
+
+rot26(str::AbstractString) = map(rot13 ∘ rot13, str)
+
+function (@main)(args)
+    foreach(arg -> print(rot26(arg), " "), args)
+    return 0
+end
+
+end
+
 end # module Rot13