1 files changed, 23 insertions, 10 deletions
diff --git a/packages/meshbay-hub/src/meshbay_hub/api/groups.py b/packages/meshbay-hub/src/meshbay_hub/api/groups.py
index 8283276..6819ff6 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/groups.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/groups.py
@@ -317,17 +317,30 @@ async def create_group(
     current_user: User = Depends(require_user_scope),
     db: AsyncSession = Depends(get_db),
 ):
+    # Being listed and being open are one question, not two.
+    #
+    # A public group that admits nobody is a contradiction: it is in the
+    # directory, so people find it and then discover they cannot get in.
+    # Admission by request was considered and dropped — between strangers the
+    # only channel is the hub, so the one-time code would travel through the
+    # very party it exists to keep out, and would protect nothing.
+    #
+    # The other way round was accepted until now and should not have been: a
+    # group anyone may join, that nobody can find, is a listing with the listing
+    # removed. Nothing could reach it but a link, and there is no link — joining
+    # goes through the node. The create form no longer offers either
+    # combination; refusing them here is what makes that true of the API too.
+    if body.visibility == "public" and body.join_policy != "open":
+        raise HTTPException(
+            status_code=422,
+            detail="A public group is open to join. Make it private if you "
+                   "want to choose who comes in.")
+    if body.visibility != "public" and body.join_policy == "open":
+        raise HTTPException(
+            status_code=422,
+            detail="A private group is invite-only. Make it public if you want "
+                   "anyone to be able to join.")
     if body.visibility == "public":
-        # A public group that admits nobody is a contradiction: it is listed in
-        # the directory, so people find it and then discover they cannot get in.
-        # Admission by request was considered and dropped — between strangers the
-        # only channel is the hub, so the one-time code would travel through the
-        # very party it exists to keep out, and would protect nothing.
-        if body.join_policy != "open":
-            raise HTTPException(
-                status_code=422,
-                detail="A public group is open to join. Make it private if you "
-                       "want to choose who comes in.")
         await _check_public_group_quota(db, current_user)
 
     desc = (body.description or "")[:512] if body.description else None