From 917c0f24167e68fe671be58fe7876490a437ad0b Mon Sep 17 00:00:00 2001
From: Colin Caine <cmcaine@gmail.com>
Date: Fri, 10 Sep 2021 17:49:18 +0100
Subject: [PATCH 1/2] Exclude modules own name from empty modules

Follow up on #40110
---
 NEWS.md                   |  2 +-
 base/boot.jl              |  2 +-
 doc/src/manual/modules.md |  2 +-
 src/module.c              | 12 +++++++-----
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index b1442f0192350..3cd65f560937b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -5,7 +5,7 @@ Julia v1.8 Release Notes
 New language features
 ---------------------
 
-* `Module(:name, false, false)` can be used to create a `module` that does not import `Core`. ([#40110])
+* `Module(:name, false, false)` can be used to create a `module` that contains no names (it does not import `Base` or `Core` and does not contain a reference to itself). ([#40110, #42154])
 * `@inline` and `@noinline` annotations can be used within a function body to give an extra
   hint about the inlining cost to the compiler. ([#41312])
 * `@inline` and `@noinline` annotations can now be applied to a function callsite or block
diff --git a/base/boot.jl b/base/boot.jl
index ee1370bf5dff1..4679acd85d26d 100644
--- a/base/boot.jl
+++ b/base/boot.jl
@@ -428,7 +428,7 @@ eval(Core, :(InterConditional(slot::Int, @nospecialize(vtype), @nospecialize(els
 eval(Core, :(MethodMatch(@nospecialize(spec_types), sparams::SimpleVector, method::Method, fully_covers::Bool) =
     $(Expr(:new, :MethodMatch, :spec_types, :sparams, :method, :fully_covers))))
 
-Module(name::Symbol=:anonymous, std_imports::Bool=true, using_core::Bool=true) = ccall(:jl_f_new_module, Ref{Module}, (Any, Bool, Bool), name, std_imports, using_core)
+Module(name::Symbol=:anonymous, std_imports::Bool=true, default_names::Bool=true) = ccall(:jl_f_new_module, Ref{Module}, (Any, Bool, Bool), name, std_imports, default_names)
 
 function _Task(@nospecialize(f), reserved_stack::Int, completion_future)
     return ccall(:jl_new_task, Ref{Task}, (Any, Any, Int), f, completion_future, reserved_stack)
diff --git a/doc/src/manual/modules.md b/doc/src/manual/modules.md
index 7d3304810a428..1135991743bb2 100644
--- a/doc/src/manual/modules.md
+++ b/doc/src/manual/modules.md
@@ -303,7 +303,7 @@ include(p) = Base.include(Mod, p)
 end
 ```
 
-If even `Core` is not wanted, a module that imports nothing at all can be defined with `Module(:YourNameHere, false, false)` and code can be evaluated into it with [`@eval`](@ref) or [`Core.eval`](@ref).
+If even `Core` is not wanted, a module that imports nothing and defines no names at all can be defined with `Module(:YourNameHere, false, false)` and code can be evaluated into it with [`@eval`](@ref) or [`Core.eval`](@ref).
 
 ### Standard modules
 
diff --git a/src/module.c b/src/module.c
index 4120b6cb9225d..a7db957d2d9c3 100644
--- a/src/module.c
+++ b/src/module.c
@@ -11,7 +11,7 @@
 extern "C" {
 #endif
 
-JL_DLLEXPORT jl_module_t *jl_new_module_(jl_sym_t *name, uint8_t using_core)
+JL_DLLEXPORT jl_module_t *jl_new_module_(jl_sym_t *name, uint8_t default_names)
 {
     jl_task_t *ct = jl_current_task;
     const jl_uuid_t uuid_zero = {0, 0};
@@ -36,11 +36,13 @@ JL_DLLEXPORT jl_module_t *jl_new_module_(jl_sym_t *name, uint8_t using_core)
     htable_new(&m->bindings, 0);
     arraylist_new(&m->usings, 0);
     JL_GC_PUSH1(&m);
-    if (jl_core_module && using_core) {
+    if (jl_core_module && default_names) {
         jl_module_using(m, jl_core_module);
     }
     // export own name, so "using Foo" makes "Foo" itself visible
-    jl_set_const(m, name, (jl_value_t*)m);
+    if (default_names) {
+        jl_set_const(m, name, (jl_value_t*)m);
+    }
     jl_module_export(m, name);
     JL_GC_POP();
     return m;
@@ -56,10 +58,10 @@ uint32_t jl_module_next_counter(jl_module_t *m)
     return jl_atomic_fetch_add(&m->counter, 1);
 }
 
-JL_DLLEXPORT jl_value_t *jl_f_new_module(jl_sym_t *name, uint8_t std_imports, uint8_t using_core)
+JL_DLLEXPORT jl_value_t *jl_f_new_module(jl_sym_t *name, uint8_t std_imports, uint8_t default_names)
 {
     // TODO: should we prohibit this during incremental compilation?
-    jl_module_t *m = jl_new_module_(name, using_core);
+    jl_module_t *m = jl_new_module_(name, default_names);
     JL_GC_PUSH1(&m);
     m->parent = jl_main_module; // TODO: this is a lie
     jl_gc_wb(m, m->parent);

From dff88cfe85546213f7cc797e050f47eca658a69d Mon Sep 17 00:00:00 2001
From: Colin Caine <cmcaine@gmail.com>
Date: Fri, 10 Sep 2021 18:01:41 +0100
Subject: [PATCH 2/2] Document Module constructor

---
 base/docs/basedocs.jl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/base/docs/basedocs.jl b/base/docs/basedocs.jl
index e7ae0123117b5..f436ebef82026 100644
--- a/base/docs/basedocs.jl
+++ b/base/docs/basedocs.jl
@@ -2812,6 +2812,13 @@ StridedVecOrMat
     Module
 
 A `Module` is a separate global variable workspace. See [`module`](@ref) and the [manual section about modules](@ref modules) for details.
+
+    Module(name::Symbol=:anonymous, std_imports=true, default_names=true)
+
+Return a module with the specified name. A `baremodule` corresponds to `Module(:ModuleName, false)`
+
+An empty module containing no names at all can be created with `Module(:ModuleName, false, false)`.
+This module will not import `Base` or `Core` and does not contain a reference to itself.
 """
 Module