Add on_grant and on_revoke callbacks (#4713)

* Add register_on_priv_grant/revoke, and on_grant/revoke to privs. Call from /grant and /revoke

* Call on_grant and on_revoke callbacks from set_privs

4 files changed, 45 insertions, 3 deletions

diff --git a/builtin/game/auth.lua b/builtin/game/auth.lua
index 7a6be8788..4d5178ba7 100644
--- a/builtin/game/auth.lua
+++ b/builtin/game/auth.lua
@@ -125,6 +125,21 @@ core.builtin_auth_handler = {
 				core.get_password_hash(name,
 					core.settings:get("default_password")))
 		end
+
+		-- Run grant callbacks
+		for priv, _ in pairs(privileges) do
+			if not core.auth_table[name].privileges[priv] then
+				core.run_priv_callbacks(name, priv, nil, "grant")
+			end
+		end
+
+		-- Run revoke callbacks
+		for priv, _ in pairs(core.auth_table[name].privileges) do
+			if not privileges[priv] then
+				core.run_priv_callbacks(name, priv, nil, "revoke")
+			end
+		end
+
 		core.auth_table[name].privileges = privileges
 		core.notify_authentication_modified(name)
 		save_auth_file()
diff --git a/builtin/game/chatcommands.lua b/builtin/game/chatcommands.lua
index 183e06a03..05b814d6f 100644
--- a/builtin/game/chatcommands.lua
+++ b/builtin/game/chatcommands.lua
@@ -132,6 +132,9 @@ local function handle_grant_command(caller, grantname, grantprivstr)
 	if privs_unknown ~= "" then
 		return false, privs_unknown
 	end
+	for priv, _ in pairs(grantprivs) do
+		core.run_priv_callbacks(grantname, priv, caller, "grant")
+	end
 	core.set_player_privs(grantname, privs)
 	core.log("action", caller..' granted ('..core.privs_to_string(grantprivs, ', ')..') privileges to '..grantname)
 	if grantname ~= caller then
@@ -193,12 +196,18 @@ core.register_chatcommand("revoke", {
 			end
 		end
 		if revoke_priv_str == "all" then
+			revoke_privs = privs
 			privs = {}
 		else
 			for priv, _ in pairs(revoke_privs) do
 				privs[priv] = nil
 			end
 		end
+
+		for priv, _ in pairs(revoke_privs) do
+			core.run_priv_callbacks(revoke_name, priv, name, "revoke")
+		end
+
 		core.set_player_privs(revoke_name, privs)
 		core.log("action", name..' revoked ('
 				..core.privs_to_string(revoke_privs, ', ')
diff --git a/builtin/game/register.lua b/builtin/game/register.lua
index ec6f28097..87d1c5659 100644
--- a/builtin/game/register.lua
+++ b/builtin/game/register.lua
@@ -65,14 +65,14 @@ local function check_modname_prefix(name)
 			error("Name " .. name .. " does not follow naming conventions: " ..
 				"\"" .. expected_prefix .. "\" or \":\" prefix required")
 		end
-		
+
 		-- Enforce that the name only contains letters, numbers and underscores.
 		local subname = name:sub(#expected_prefix+1)
 		if subname:find("[^%w_]") then
 			error("Name " .. name .. " does not follow naming conventions: " ..
 				"contains unallowed characters")
 		end
-		
+
 		return name
 	end
 end
@@ -435,6 +435,17 @@ function core.run_callbacks(callbacks, mode, ...)
 	return ret
 end
 
+function core.run_priv_callbacks(name, priv, caller, method)
+	if not core.registered_privileges[priv]["on_" .. method] or
+			core.registered_privileges[priv]["on_" .. method](name, caller) then
+		for _, func in ipairs(core["registered_on_priv_" .. method]) do
+			if not func(name, caller) then
+				break
+			end
+		end
+	end
+end
+
 --
 -- Callback registration
 --
@@ -553,10 +564,11 @@ core.registered_craft_predicts, core.register_craft_predict = make_registration(
 core.registered_on_protection_violation, core.register_on_protection_violation = make_registration()
 core.registered_on_item_eats, core.register_on_item_eat = make_registration()
 core.registered_on_punchplayers, core.register_on_punchplayer = make_registration()
+core.registered_on_priv_grant, core.register_on_priv_grant = make_registration()
+core.registered_on_priv_revoke, core.register_on_priv_revoke = make_registration()
 
 --
 -- Compatibility for on_mapgen_init()
 --
 
 core.register_on_mapgen_init = function(func) func(core.get_mapgen_params()) end
-
diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 5b071d626..6ff9c9433 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -2446,6 +2446,12 @@ Call these functions only at load time!
     * `definition`: `{ description = "description text", give_to_singleplayer = boolean}`
       the default of `give_to_singleplayer` is true
     * To allow players with `basic_privs` to grant, see `basic_privs` minetest.conf setting.
+    * `on_grant(name, granter_name)`: Called when given to player `name` by `granter_name`.
+         `granter_name` will be nil if the priv was granted by a mod.
+    * `on_revoke(name, revoker_name)`: Called when taken from player `name` by `revoker_name`.
+         `revoker_name` will be nil if the priv was revoked by a mod
+    * Note that the above two callbacks will be called twice if a player is responsible - 
+      once with the player name, and then with a nil player name.
 * `minetest.register_authentication_handler(handler)`
     * See `minetest.builtin_auth_handler` in `builtin.lua` for reference