feat: implement tostring for SemverImpl

* `SemverImpl:__tostring` - Allows for stringifying a parsed semver instance
* Add TODO comment for future erroring for bad ordinal format

lib/init.luau

@@ -296,6 +296,8 @@ function Semver.parse(ver: string): SemverResult<SemverImpl>
 					local potentialOrdinalNumber, potentialBuildMetadata = string.match(components[4], "(%d)+(.*)")
 					if potentialOrdinalNumber == nil then
 						return badPrereleaseType(components[4])
+						-- TODO: If there are components after the 4th index, we
+						-- should error
 					end
 
 					if potentialBuildMetadata ~= nil then
@@ -395,4 +397,24 @@ function Semver.__le(left: SemverImpl, right: SemverImpl): boolean
 		else prereleaseLe(left.prerelease:unwrapOrNil(), right.prerelease:unwrapOrNil())
 end
 
+function Semver.__tostring(self: SemverImpl): string
+	local base = `{self.major}.{self.minor}.{self.patch}`
+	local prerelease = self.prerelease
+		:map(function(prerelease: PrereleaseVersion)
+			return `-{prerelease.type}{prerelease.ordinal
+				:map(function(ord: number)
+					return `.{ord}`
+				end)
+				:unwrapOr("")}`
+		end)
+		:unwrapOr("")
+	local build = self.buildMetadata
+		:map(function(buildMetadata: string)
+			return `+{buildMetadata}`
+		end)
+		:unwrapOr("")
+
+	return base .. prerelease .. build
+end
+
 return Semver

tests/tostring.luau

@@ -0,0 +1,33 @@
+local frktest = require("@pkg/frktest")
+local test = frktest.test
+local check = frktest.assert.check
+
+local Option = require("../luau_packages/option")
+type Option<T> = Option.Option<T>
+
+local Semver = require("../lib")
+
+return function()
+	test.suite("Stringification tests", function()
+		test.case("A parsed version when stringified should not change", function()
+			local versions = {
+				"1.2.3",
+				"1.0.0-alpha",
+				"2.3.4-beta.1",
+				"3.0.0-rc.1+build.123",
+				"4.5.6+sha.xyz",
+				"5.0.0-alpha.1+build.999",
+				"6.7.8-beta.2+exp.sha.5114f85",
+				"7.0.0-alpha.1",
+				"9.9.9+20230615",
+			}
+
+			for _, version in versions do
+				local parsed = Semver.parse(version):unwrap()
+				local stringified = tostring(parsed)
+
+				check.equal(stringified, version)
+			end
+		end)
+	end)
+end