ClojureScript
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1.10.741 Release

24 April 2020
ClojureScript Team

We’re happy to announce a new release of ClojureScript. If you’re an existing user of ClojureScript please read over the following release notes carefully, there are two very significant changes. First, ClojureScript now ships with greatly enhanced support for integration with popular JavaScript bundling tools such as Webpack and Metro. Second, due to continuing changes to Google Closure Compiler and Library, we’ve decided to drop support for the Rhino and Nashorn REPLs to lower the maintenance burden around releases.

Noteworthy Changes

  • Closure Compiler has been updated to v20200112

  • Closure Library has been updated to 0.0-20191016-6ae1f72f

  • Rhino, Nashorn, and GraalJS REPLs have been removed

The latest Closure Compiler & Library releases included a number of breaking changes which significantly increased the maintenance burden for this release. Given Closure Compiler & Library’s recent pace of change, we’ve decided to focus our energies on the essential browser and Node.js REPLs. We’ve also begun enrichening the CLI & REPL APIs to ease third party efforts to target these JavaScript environments.

New Core Features

JavaScript Bundler Support

  • :target :bundle

  • :bundle-cmd

  • :target-fn

  • A new --install-deps CLI option

We’re happy to announce a significant new feature - the :bundle target. This target generates output that can be fed directly into popular JavaScript bundlers such as Webpack and Metro (for React Native). Not only does this greatly ease usage of Node modules, library creators can now distribute ClojureScript artifacts that depend on Node modules and be confident that users can consume these artifacts regardless of which build tool they may prefer.

There’s much more to say about the :bundle target, and we’ll be releasing a separate post and guide soon.

Iterator Support

It is now possible to call seq on any object implementing JavaScript’s Iterator protocol. A new core predicate, cljs.core/js-iterable? is introduced with this feature.

For example, (js-iterable? (js/Set.)) is true and

(-> (doto (js/Set.) (.add 1) (.add 2))
  seq)

can now produce (1 2).

Symbol Support

A new core predicate cljs.core/js-symbol? has been added and printing has been revised to allow printing of symbols:

cljs.user=> (js/Symbol "abc")
#object[Symbol(abc)]

Warning Improvements

Single arity arithmetic operations will now warn on bad arguments:

cljs.user=> (+ "foo")
WARNING: cljs.core/+, all arguments must be numbers, got [string] instead at line 1 <cljs repl>

Performance Improvements

  • re-pattern, re-matches, and re-find are now faster

  • Code gen better facilitates protocol static dispatch inlining

  • Fast initial prompt for browser REPL

  • Output size minimized for trivial "Hello World" programs

Change List

For a complete list of updates in ClojureScript 1.10.741 see Changes.

Contributors

Thanks to all of the community members who contributed to ClojureScript 1.10.741:

  • Camilo Polymeris

  • Colin Kahn

  • Dieter Komendera

  • Dominic Monroe

  • Roman Liutikov