Add error section to Lua style

This commit is contained in:
Talia 2019-07-18 11:02:26 +02:00
parent 96ccee0943
commit 1abcbc2894

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@ -166,3 +166,35 @@ Example:
local ages = { [20]="John, Henry"; [21]="William"; } local ages = { [20]="John, Henry"; [21]="William"; }
local errors = { [1]="File not Found"; [2]="Permission Denied" } local errors = { [1]="File not Found"; [2]="Permission Denied" }
# Errors
1. On error, functions should return `nil` + error message
2. Whenever possible, an identifier should be passed as the third argument
Explanation:
`nil` + message is a widely used convention for returning errors in Lua.
However, error messages are not guaranteed to remain unchanged,
this they are poorly suited to identify an error programatically.
Thus it makes sense to pass a third value that can be used to identify an error
condition. This can be a numeric error code, a string or a unique table.
Example:
local function divide(dividend, divisor)
if divisor == 0 then
return nil, 'Attempting to divide by 0', 'division-by-0'
else
return dividend / divisor
end
end
1. Libraries should never raise errors to the calling code.
Explanation:
Because error-handling mechanisms in Lua are very simple
and there is no mechanism like 'rescue' blocks,
errors are hard to deal with in section of code that require cleanup operations
to keep state (be it internal or external) consistent.