feat(lib): only download asset when it is of a valid format

Small optimization to not fetch an asset if its need of a supported
compression format.

toolchainlib/src/init.luau

@@ -46,17 +46,15 @@ local function downloadAndDecompress(asset: {
 	size: number,
 	content_type: string,
 }): Option<pathfs.Path>
-	-- TODO: Small optimization by first detecting that its a valid format we support
-	-- before downloading the file
-	local contentsResp = net.request(asset.browser_download_url)
-	if not contentsResp.ok then
-		return error(`Failed to download asset {asset.name}: HTTP Code {contentsResp.statusCode}`)
-	end
-
 	return compression
 			.detectFormat(asset.name)
-			:map(function(format: compression.CompressionFormat)
+			:andThen(function(format: compression.CompressionFormat)
-				return compression.decompress[format](buffer.fromstring(contentsResp.body)):unwrap() :: pathfs.Path
+				local contentsResp = net.request(asset.browser_download_url)
+				if not contentsResp.ok then
+					return error(`Failed to download asset {asset.name}: HTTP Code {contentsResp.statusCode}`)
+				end
+
+				return compression.decompress[format](buffer.fromstring(contentsResp.body)):ok() :: Option<pathfs.Path>
 			end) :: Option<pathfs.Path>
 end
 

toolchainlib/src/utils/result_option_conv.luau

@@ -7,14 +7,20 @@ local Option = {}
 local Result = {}
 
 export type Option<T> = OptionImpl.Option<T> & typeof(Option)
-export type Result<T, E> = ResultImpl.Result<T, E>
+export type Result<T, E> = ResultImpl.Result<T, E> & typeof(Result)
 
 function Option.okOr<T, E>(self: Option<T>, err: E): Result<T, E>
 	return self:mapOrElse(function()
 		return ResultImpl.Err(err)
 	end, function(val)
 		return ResultImpl.Ok(val)
-	end)
+	end) :: Result<T, E>
+end
+
+function Result.ok<T, E>(self: Result<T, E>): Option<T>
+	return self:mapOr(OptionImpl.None, function(val: T)
+		return OptionImpl.Some(val)
+	end) :: Option<T>
 end
 
 return {