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---@class Failure
---@field error any
local Failure = {}
Failure.__index = Failure
function Failure.new(error)
return setmetatable({ error = error }, Failure)
end
---@class Result
---@field value any
local Result = {}
Result.__index = Result
function Result.new(value)
return setmetatable({
value = value,
}, Result)
end
function Result.success(value)
return Result.new(value)
end
function Result.failure(error)
return Result.new(Failure.new(error))
end
function Result:get_or_nil()
if self:is_success() then
return self.value
end
end
function Result:get_or_else(value)
if self:is_success() then
return self.value
else
return value
end
end
---@param exception any @(optional) The exception to throw if the result is a failure.
function Result:get_or_throw(exception)
if self:is_success() then
return self.value
else
if exception ~= nil then
error(exception, 2)
else
error(self.value.error, 2)
end
end
end
function Result:err_or_nil()
if self:is_failure() then
return self.value.error
end
end
function Result:is_failure()
return getmetatable(self.value) == Failure
end
function Result:is_success()
return getmetatable(self.value) ~= Failure
end
---@param mapper_fn fun(value: any): any
function Result:map(mapper_fn)
if self:is_success() then
return Result.success(mapper_fn(self.value))
else
return self
end
end
---@param mapper_fn fun(value: any): any
function Result:map_catching(mapper_fn)
if self:is_success() then
local ok, result = pcall(mapper_fn, self.value)
if ok then
return Result.success(result)
else
return Result.failure(result)
end
else
return self
end
end
---@param recover_fn fun(value: any): any
function Result:recover(recover_fn)
if self:is_failure() then
return Result.success(recover_fn(self:err_or_nil()))
else
return self
end
end
---@param recover_fn fun(value: any): any
function Result:recover_catching(recover_fn)
if self:is_failure() then
local ok, value = pcall(recover_fn, self:err_or_nil())
if ok then
return Result.success(value)
else
return Result.failure(value)
end
else
return self
end
end
---@param fn fun(): any
---@return Result
function Result.run_catching(fn)
local ok, result = pcall(fn)
if ok then
return Result.success(result)
else
return Result.failure(result)
end
end
return Result
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