1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
|
---@generic T
---@class Failure<T>
---@field error T
local Failure = {}
Failure.__index = Failure
---@param error T
function Failure:new(error)
---@type Failure<T>
local instance = {}
setmetatable(instance, self)
instance.error = error
return instance
end
---@generic T, E
---@class Result<T, E = any>
---@field value T | Failure<E>
local Result = {}
Result.__index = Result
---@param value T
function Result:new(value)
---@type Result<T>
local instance = {}
setmetatable(instance, self)
instance.value = value
return instance
end
---@generic U
---@param value U
---@return Result<U>
function Result.success(value)
return Result:new(value)
end
---@generic U
---@param error U
---@return Result<T, U>
function Result.failure(error)
return Result:new(Failure:new(error))
end
---@return T?
function Result:get_or_nil()
if self:is_success() then
return self.value
end
end
---@generic V
---@param value V
---@return T | V
function Result:get_or_else(value)
if self:is_success() then
return self.value
else
return value
end
end
---@param exception any? The exception to throw if the result is a failure.
---@return T
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
---@return E?
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
---@generic U
---@param mapper_fn fun(value: T): U
---@return Result<U>
function Result:map(mapper_fn)
if self:is_success() then
return Result.success(mapper_fn(self.value))
else
return self
end
end
---@generic U
---@param mapper_fn fun(error: E): U
---@return Result<T, U>
function Result:map_err(mapper_fn)
if self:is_failure() then
return Result.failure(mapper_fn(self.value.error))
else
return self
end
end
---@generic U
---@param mapper_fn fun(value: T): U
---@return Result<U>
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
---@generic U
---@param recover_fn fun(err: E): U
---@return Result<T | U, E>
function Result:recover(recover_fn)
if self:is_failure() then
return Result.success(recover_fn(self:err_or_nil()))
else
return self
end
end
---@generic U
---@param recover_fn fun(err: E): U
---@return Result<T | U, E>
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(err: E)
function Result:on_failure(fn)
if self:is_failure() then
fn(self.value.error)
end
return self
end
---@param fn fun(value: T)
function Result:on_success(fn)
if self:is_success() then
fn(self.value)
end
return self
end
function Result:ok()
local Optional = require "mason-core.optional"
if self:is_success() then
return Optional.of(self.value)
else
return Optional.empty()
end
end
---@generic U
---@param fn fun(value: T): Result<U, E>
---@return Result<T | U, E>
function Result:and_then(fn)
if self:is_success() then
return fn(self.value)
else
return self
end
end
---@generic U
---@param fn fun(err: E): Result<T, U>
function Result:or_else(fn)
if self:is_failure() then
return fn(self:err_or_nil())
else
return self
end
end
---@generic U
---@param fn fun(): U
---@return Result<U>
function Result.run_catching(fn)
local ok, result = pcall(fn)
if ok then
return Result.success(result)
else
return Result.failure(result)
end
end
---@generic T, U
---@param fn fun(try: fun(result: Result<T>): T): U
---@return Result<U>
function Result.try(fn)
local thread = coroutine.create(fn)
local step
step = function(...)
local results = { coroutine.resume(thread, ...) }
local ok, result = results[1], results[2]
if not ok then
return Result.failure(result)
end
if coroutine.status(thread) == "dead" then
if getmetatable(result) == Result then
return result
else
return Result.success(result)
end
elseif getmetatable(result) == Result then
if result:is_failure() then
return result
else
return step(result:get_or_nil())
end
else
-- yield to parent coroutine
return step(coroutine.yield(result, unpack(results, 3)))
end
end
return step(coroutine.yield)
end
---@generic U
---@param fn fun(...: any): U
---@return Result<U>
function Result.pcall(fn, ...)
local ok, res = pcall(fn, ...)
if ok then
return Result.success(res)
else
return Result.failure(res)
end
end
return Result
|
