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Fix & clarify definition of global declaration

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Lars Müller 2022-06-30 20:06:21 +02:00 committed by GitHub
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doc/environment.adoc
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@ -26,7 +26,20 @@ Variables in Lua are global by default (both assignment and access). This often
. Missspelling a local variable and accessing a global variable instead (which will usually be `nil`)
. Forgetting `local` when assigning to a variable, (over)writing a global variable, leading to "global pollution"
Minetest's built-in strictness works using a metatable on the global table and will log warnings for both cases. Minetest defines a global declaration as a *global assignment at load time*.
Minetest's built-in strictness works using a metatable on the global table and will log warnings for both cases. Minetest defines a global declaration as a *global assignment in a main chunk* - setting globals in any other function will not be considered a declaration and will trigger a warning:
[source, lua]
----
-- Declarations according to Minetest's definition:
global_var = 42
for k, v in pairs{a = 1, b = 2} do _G[k] = v end
-- Assignment to undeclared global:
local function set_global()
another_global_var = 42
end
set_global()
----
. Reading an undeclared global variable will trigger an "undeclared global variable access" warning
. Setting an undeclared global variable after load time will trigger an "assignment to undeclared global" warning