Today we’re excited to announce our Release Candidate of TypeScript 5.2!\nBetween now and the stable release of TypeScript 5.2, we expect no further changes apart from critical bug fixes.<\/p>\n
To get started using the RC, you can get it through NuGet<\/a>, or through npm with the following command:<\/p>\n Here’s a quick list of what’s new in TypeScript 5.2!<\/p>\n Since the Beta<\/a>, we’ve added a type-checking optimization<\/a> and made it possible to reference the paths of TypeScript implementation files in type-only imports<\/a>.<\/p>\n TypeScript 5.2 adds support for the upcoming Explicit Resource Management<\/a> feature in ECMAScript.\nLet’s explore some of the motivations and understand what the feature brings us.<\/p>\n It’s common to need to do some sort of "clean-up" after creating an object.\nFor example, you might need to close network connections, delete temporary files, or just free up some memory.<\/p>\n Let’s imagine a function that creates a temporary file, reads and writes to it for various operations, and then closes and deletes it.<\/p>\n This is fine, but what happens if we need to perform an early exit?<\/p>\n We’re starting to see some duplication of clean-up which can be easy to forget.\nWe’re also not guaranteed to close and delete the file if an error gets thrown.\nThis could be solved by wrapping this all in a While this is more robust, it’s added quite a bit of "noise" to our code.\nThere are also other foot-guns we can run into if we start adding more clean-up logic to our This starts by adding a new built-in npm install -D typescript@rc<\/span>\r\n<\/code><\/pre>\n\n
using<\/code> Declarations and Explicit Resource Management<\/a><\/li>\nWhat’s New Since the Beta?<\/h2>\n
using<\/code> Declarations and Explicit Resource Management<\/h2>\nimport<\/span> <\/span>*<\/span> <\/span>as<\/span> <\/span>fs<\/span> <\/span>from<\/span> <\/span>"fs"<\/span>;<\/span>\r\n\r\nexport<\/span> <\/span>function<\/span> <\/span>doSomeWork<\/span>() {<\/span>\r\n <\/span>const<\/span> <\/span>path<\/span> = <\/span>".some_temp_file"<\/span>;<\/span>\r\n <\/span>const<\/span> <\/span>file<\/span> = <\/span>fs<\/span>.<\/span>openSync<\/span>(<\/span>path<\/span>, <\/span>"w+"<\/span>);<\/span>\r\n\r\n <\/span>\/\/ use file...<\/span>\r\n\r\n <\/span>\/\/ Close the file and delete it.<\/span>\r\n <\/span>fs<\/span>.<\/span>closeSync<\/span>(<\/span>file<\/span>);<\/span>\r\n <\/span>fs<\/span>.<\/span>unlinkSync<\/span>(<\/span>path<\/span>);<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\nexport<\/span> <\/span>function<\/span> <\/span>doSomeWork<\/span>() {<\/span>\r\n <\/span>const<\/span> <\/span>path<\/span> = <\/span>".some_temp_file"<\/span>;<\/span>\r\n <\/span>const<\/span> <\/span>file<\/span> = <\/span>fs<\/span>.<\/span>openSync<\/span>(<\/span>path<\/span>, <\/span>"w+"<\/span>);<\/span>\r\n\r\n <\/span>\/\/ use file...<\/span>\r\n <\/span>if<\/span> (<\/span>someCondition<\/span>()) {<\/span>\r\n <\/span>\/\/ do some more work...<\/span>\r\n\r\n <\/span>\/\/ Close the file and delete it.<\/span>\r\n <\/span>fs<\/span>.<\/span>closeSync<\/span>(<\/span>file<\/span>);<\/span>\r\n <\/span>fs<\/span>.<\/span>unlinkSync<\/span>(<\/span>path<\/span>);<\/span>\r\n <\/span>return<\/span>;<\/span>\r\n }<\/span>\r\n\r\n <\/span>\/\/ Close the file and delete it.<\/span>\r\n <\/span>fs<\/span>.<\/span>closeSync<\/span>(<\/span>file<\/span>);<\/span>\r\n <\/span>fs<\/span>.<\/span>unlinkSync<\/span>(<\/span>path<\/span>);<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\ntry<\/code>\/finally<\/code> block.<\/p>\nexport<\/span> <\/span>function<\/span> <\/span>doSomeWork<\/span>() {<\/span>\r\n <\/span>const<\/span> <\/span>path<\/span> = <\/span>".some_temp_file"<\/span>;<\/span>\r\n <\/span>const<\/span> <\/span>file<\/span> = <\/span>fs<\/span>.<\/span>openSync<\/span>(<\/span>path<\/span>, <\/span>"w+"<\/span>);<\/span>\r\n\r\n <\/span>try<\/span> {<\/span>\r\n <\/span>\/\/ use file...<\/span>\r\n\r\n <\/span>if<\/span> (<\/span>someCondition<\/span>()) {<\/span>\r\n <\/span>\/\/ do some more work...<\/span>\r\n <\/span>return<\/span>;<\/span>\r\n }<\/span>\r\n }<\/span>\r\n <\/span>finally<\/span> {<\/span>\r\n <\/span>\/\/ Close the file and delete it.<\/span>\r\n <\/span>fs<\/span>.<\/span>closeSync<\/span>(<\/span>file<\/span>);<\/span>\r\n <\/span>fs<\/span>.<\/span>unlinkSync<\/span>(<\/span>path<\/span>);<\/span>\r\n }<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\nfinally<\/code> block \u2014 for example, exceptions preventing other resources from being disposed.\nThis is what the explicit resource management<\/a> proposal aims to solve.\nThe key idea of the proposal is to support resource disposal \u2014 this clean-up work we’re trying to deal with \u2014 as a first class idea in JavaScript.<\/p>\nsymbol<\/code> called Symbol.dispose<\/code>, and we can create objects with methods named by Symbol.dispose<\/code>.\nFor convenience, TypeScript defines a new global type called Disposable<\/code> which describes these.<\/p>\nclass<\/span> <\/span>TempFile<\/span> <\/span>implements<\/span> <\/span>Disposable<\/span> {<\/span>\r\n <\/span>#path<\/span>: <\/span>