From ef451dace696bd5d437c71f4ff08c7ffa1a7aebb Mon Sep 17 00:00:00 2001
From: Erica Marigold <hi@devcomp.xyz>
Date: Mon, 1 Apr 2024 16:00:55 +0530
Subject: [PATCH] feat: finalize `Option` & `Result` implementations

---
 lib/conversion.luau |  97 ++++++++++++++++++++
 lib/option.luau     | 218 +++++++++++++++++++++++++++++++++++++++++++-
 lib/result.luau     |  49 +---------
 3 files changed, 315 insertions(+), 49 deletions(-)
 create mode 100644 lib/conversion.luau

diff --git a/lib/conversion.luau b/lib/conversion.luau
new file mode 100644
index 0000000..e77e38e
--- /dev/null
+++ b/lib/conversion.luau
@@ -0,0 +1,97 @@
+--[[
+	This exists because if the Option module were to have methods to convert
+	to Result, and the Result module were to have methods to convert to Option,
+	there would be a cyclic dependency.
+
+	So, if a consumer of this library wants to convert between the two, they
+	would rather import this conversion module.
+]]
+
+local option = require("option")
+local Option = option.Option
+export type Option<T> = option.Option<T>
+local None = option.None
+local Some = option.Some
+
+local result = require("result")
+local Result = result.Result
+export type Result<T, E> = result.Result<T, E>
+local Ok = result.Ok
+local Err = result.Err
+
+function Result.ok<T, E>(self: Result<T, E>): Option<T>
+	if self:isOk() then
+		if self._value == nil then
+			return None()
+		end
+
+		return Some(self._value)
+	end
+
+	return None()
+end
+
+function Result.err<T, E>(self: Result<T, E>): Option<E>
+	if self:isErr() then
+		return Option.new(self._error) :: Option<E>
+	end
+
+	return None()
+end
+
+function Result.transpose<T, E>(self: Result<Option<T>, E>): Option<Result<T, E>>
+	-- TODO: Instead of checking whether values are nil, use
+	-- utility methods for Options once available
+	if self._value == None() then
+		return None()
+	elseif self:isOkAnd(function(val): boolean
+		return val._optValue == nil
+	end) then
+		return Some(Ok(self._value._optValue))
+	elseif self:isErr() then
+		return Some(Err(self._error))
+	end
+
+	error("`Result` is not transposable")
+end
+
+function Option.okOr<T, E>(self: Option<T>, err: E): Result<T, E>
+	if self:isSome() then
+		return Ok(self._optValue)
+	end
+
+	return Err(err)
+end
+
+function Option.okOrElse<T, E>(self: Option<T>, err: () -> E): Result<T, E>
+	if self:isSome() then
+		return Ok(self._optValue :: T)
+	end
+
+	return Err(err())
+end
+
+function Option.transpose<T, E>(self: Option<Result<T, E>>): Result<Option<T>, E>
+	if self:isSome() then
+		local inner = self._optValue
+		assert(self.typeId == "Option" and inner.typeId == "Result", "Only an `Option` of a `Result` can be transposed")
+
+		if inner:isOk() then
+			return Some(Ok(inner._value))
+		elseif inner:isErr() then
+			return Some(Err(inner._error))
+		end
+	end
+
+	return Ok(None())
+end
+
+return {
+	Ok = Ok,
+	Err = Err,
+	Result = Result,
+
+	Some = Some,
+	None = None,
+	Option = Option,
+}
diff --git a/lib/option.luau b/lib/option.luau
index 13e4828..850ed96 100644
--- a/lib/option.luau
+++ b/lib/option.luau
@@ -30,11 +30,227 @@ function Option.new<T>(val: T?)
 				end
 			end,
 		}
+
+		-- TODO: Implement equality and arithmetic metamethods
+		-- TODO: Implement __iter, once iterators traits exist
 	)
 end
 
+function Option.isSome<T>(self: Option<T>): boolean
+	return self._optValue ~= nil
+end
+
+function Option.isSomeAnd<T>(self: Option<T>, op: (val: T) -> boolean): boolean
+	-- We know that it's not None, so this is fine
+	return self:isSome() and op(self._optValue :: T)
+end
+
+function Option.isNone<T>(self: Option<T>): boolean
+	return not self:isSome()
+end
+
+function Option.expect<T>(self: Option<T>, msg: string): T | never
+	if self:isSome() then
+		return self._optValue :: T
+	end
+
+	return error(`panic: {msg}; expected Option to be type Option::Some(T), got Option::None`)
+end
+
+function Option.unwrap<T>(self: Option<T>): T | never
+	if self:isSome() then
+		return self._optValue :: T
+	end
+
+	return error("called `Option:unwrap()` on a `None` value")
+end
+
+function Option.unwrapOr<T>(self: Option<T>, default: T): T
+	if self:isSome() then
+		return self._optValue :: T
+	end
+
+	return default
+end
+
+function Option.unwrapOrElse<T>(self: Option<T>, default: () -> T): T
+	if self:isSome() then
+		return self._optValue :: T
+	end
+
+	return default()
+end
+
+function Option.map<T, U>(self: Option<T>, op: (x: T) -> U?): Option<U>
+	if self:isSome() then
+		local val = op(self._optValue :: T)
+
+		if val == nil then
+			return None()
+		end
+
+		return Some(val)
+	end
+
+	return None()
+end
+
+function Option.inspect<T>(self: Option<T>, op: (x: T) -> nil): Option<T>
+	if self:isSome() then
+		op(self._optValue :: T)
+	end
+
+	return self
+end
+
+function Option.mapOr<T, U>(self: Option<T>, default: U, op: (val: T) -> U)
+	if self:isSome() then
+		return op(self._optValue :: T)
+	end
+
+	return default
+end
+
+function Option.mapOrElse<T, U>(self: Option<T>, default: () -> U, op: (val: T) -> U): U
+	if self:isSome() then
+		return op(self._optValue :: T)
+	end
+
+	return default()
+end
+
+-- TODO: Iterator traits
+function Option.iter() end
+
+function Option.and_<T, U>(self: Option<T>, optb: Option<U>): Option<U>
+	if self:isSome() then
+		return optb
+	end
+
+	return None()
+end
+
+function Option.andThen<T, U>(self: Option<T>, op: (val: T) -> Option<U>): Option<U>
+	if self:isSome() then
+		return op(self._optValue :: T)
+	end
+
+	return None()
+end
+
+function Option.filter<T>(self: Option<T>, predicate: (val: T) -> boolean): Option<T>
+	if self:isSome() then
+		if predicate(self._optValue :: T) then
+			return self
+		end
+	end
+
+	return None()
+end
+
+function Option.or_<T>(self: Option<T>, optb: Option<T>): Option<T>
+	if self:isSome() then
+		return self
+	end
+
+	return optb
+end
+
+function Option.orElse<T>(self: Option<T>, op: () -> Option<T>): Option<T>
+	if self:isSome() then
+		return self
+	end
+
+	return op()
+end
+
+function Option.xor<T>(self: Option<T>, optb: Option<T>): Option<T>
+	if self:isSome() and optb:isSome() then
+		return None()
+	end
+
+	if self:isSome() then
+		return self
+	elseif optb:isSome() then
+		return optb
+	end
+
+	return None()
+end
+
+function Option.insert<T>(self: Option<T>, val: T): T
+	self._optValue = val
+	return self._optValue :: T
+end
+
+function Option.getOrInsert<T>(self: Option<T>, val: T): T
+	if self:isNone() then
+		self._optValue = val
+	end
+
+	return self._optValue :: T
+end
+
+function Option.take<T>(self: Option<T>): Option<T>
+	if self:isSome() then
+		local val = self._optValue :: T
+		self._optValue = nil
+		return Some(val)
+	end
+
+	return None()
+end
+
+function Option.replace<T>(self: Option<T>, val: T): Option<T>
+	local current: Option<T> = self
+	self._optValue = val
+
+	if current:isNone() then
+		return current
+	end
+
+	return Some(current._optValue :: T)
+end
+
+function Option.contains<T>(self: Option<T>, val: T): boolean
+	if self:isSome() then
+		return self._optValue == val
+	end
+
+	return false
+end
+
+function Option.zip<T, U>(self: Option<T>, other: Option<U>): Option<{ T | U }>
+	if self:isSome() and other:isSome() then
+		return Some({ self._optValue, other._optValue })
+	end
+
+	return None()
+end
+
+function Option.zipWith<T, U, R>(self: Option<T>, other: Option<U>, op: (x: T, y: U) -> R?): Option<R>
+	if self:isSome() and other:isSome() then
+		local computed = op(self._optValue :: T, other._optValue :: U)
+
+		if computed ~= nil then
+			return Some(computed :: R)
+		end
+	end
+
+	return None()
+end
+
+function Option.unzip<T, A, B>(self: Option<T>): (Option<A>, Option<B>)
+	if self:isSome() then
+		if self:isSome() and typeof(self._optValue) == "table" and #self._optValue == 2 then
+			return Some(self._optValue[1] :: A), Some(self._optValue[2] :: B)
+		end
+	end
+
+	return None(), None()
+end
+
 return {
-	-- TODO: Implement Option utility methods
 	Option = Option,
 	Some = Some,
 	None = None,
diff --git a/lib/result.luau b/lib/result.luau
index 8a89be0..d59beab 100644
--- a/lib/result.luau
+++ b/lib/result.luau
@@ -1,9 +1,3 @@
-local option = require("option")
-local Option = option.Option
-type Option<T> = option.Option<T>
-local None = option.None
-local Some = option.Some
-
 local Result = {}
 export type Result<T, E> = typeof(Result) & {
 	_value: T,
@@ -52,6 +46,7 @@ function Result.new<T, E>(val: T, err: E)
 				error(`eq: cannot compare {tostring(self)} and {tostring(other)}`)
 			end,
 
+			-- TODO: Implement equality and arithmetic metamethods
 			-- TODO: Implement __iter, once iterators traits exist
 		}
 	)
@@ -81,26 +76,6 @@ function Result.isErrAnd<T, E>(self: Result<T, E>, predicate: (val: E) -> boolea
 	return false
 end
 
-function Result.ok<T, E>(self: Result<T, E>): Option<T>
-	if self:isOk() then
-		if self._value == nil then
-			return None()
-		end
-
-		return Some(self._value)
-	end
-
-	return None()
-end
-
-function Result.err<T, E>(self: Result<T, E>): Option<E>
-	if self:isErr() then
-		return Option.new(self._error) :: Option<E>
-	end
-
-	return None()
-end
-
 function Result.map<T, E, U>(self: Result<T, E>, op: (val: T) -> U): Result<U, E>
 	if self:isOk() then
 		return Result.new(op(self._value), self._error) :: Result<U, E>
@@ -260,30 +235,8 @@ function Result.containsErr<T, E>(self: Result<T, E>, err: E): boolean
 	return false
 end
 
-function Result.transpose<T, E>(self: Result<Option<T>, E>): Option<Result<T, E>>
-	-- TODO: Instead of checking whether values are nil, use
-	-- utility methods for Options once available
-	if self._value == None() then
-		return None()
-	elseif self:isOkAnd(function(val): boolean
-		return val._optValue == nil
-	end) then
-		return Some(Ok(self._value._optValue))
-	elseif self:isErr() then
-		return Some(Err(self._error))
-	end
-
-	error("`Result` is not transposable")
-end
-
-local x: Result<Option<string>, string> = Ok(None())
-
-print(tostring(x))
-
 return {
 	Ok = Ok,
 	Err = Err,
 	Result = Result,
 }
-
--- print(y:transpose()) -- this should have a typeerror, i need to fix this