Merge pull request #668 from sjrd/scalajs-1.20.2

Announcing Scala.js 1.20.2.

Author: sjrd

_config.yml

@@ -64,7 +64,7 @@ colors:  #in hex code if not noted else
 
 ### VERSIONS ###
 versions:
-  scalaJS: 1.20.1
+  scalaJS: 1.20.2
   scalaJSBinary: 1
   scalaJS06x: 0.6.33
   scalaJS06xBinary: 0.6

_posts/news/2026-01-05-announcing-scalajs-1.20.2.md

@@ -0,0 +1,95 @@
+---
+layout: post
+title: Announcing Scala.js 1.20.2
+category: news
+tags: [releases]
+permalink: /news/2026/01/05/announcing-scalajs-1.20.2/
+---
+
+
+We are pleased to announce the release of Scala.js 1.20.2!
+
+This release comes with even more performance improvements to the WebAssembly and JavaScript backends alike.
+
+The Scala standard library has been upgraded to match Scala 2.12.21 and 2.13.17.
+
+Read on for more details.
+
+<!--more-->
+
+## Getting started
+
+If you are new to Scala.js, head over to [the tutorial]({{ BASE_PATH }}/tutorial/).
+
+If you need help with anything related to Scala.js, you may find our community [in `#scala-js` on Discord](https://discord.com/invite/scala) and [on Stack Overflow](https://stackoverflow.com/questions/tagged/scala.js).
+
+Bug reports can be filed [on GitHub](https://github.com/scala-js/scala-js/issues).
+
+## Release notes
+
+If upgrading from Scala.js 0.6.x, make sure to read [the release notes of Scala.js 1.0.0]({{ BASE_PATH }}/news/2020/02/25/announcing-scalajs-1.0.0/) first, as they contain a host of important information, including breaking changes.
+
+This is a **patch** release:
+
+* It is backward binary compatible with all earlier versions in the 1.x series: libraries compiled with 1.0.x through 1.20.1 can be used with 1.20.2 without change.
+* It is forward binary compatible with 1.20.0 and 1.20.1: libraries compiled with 1.20.2 can be used with previous 1.20.x versions without change.
+* It is backward source compatible with 1.20.0 and 1.20.1: source code that used to compile with previous 1.20.x versions should compile as is when upgrading to 1.20.2.
+
+In addition, like Scala.js 1.20.0 and 1.20.1:
+
+* It is *not* forward binary compatible with 1.19.x: libraries compiled with 1.20.2 cannot be used with 1.19.x or earlier.
+* It is *not* entirely backward source compatible with 1.19.x: it is not guaranteed that a codebase will compile *as is* when upgrading from 1.19.x or earlier (in particular in the presence of `-Xfatal-warnings`).
+
+As a reminder, libraries compiled with 0.6.x cannot be used with Scala.js 1.x; they must be republished with 1.x first.
+
+## Enhancements
+
+### Performance improvements
+
+Scala.js 1.20.2 brings a number of performance improvements compared to 1.20.1.
+These come in addition to the improvements shipped in 1.20.1.
+
+For both JavaScript and WebAssembly:
+
+* Micro-optimizations in low-level methods in `java.lang.Math`, `Float`, and `Double`.
+* Various new micro-optimizations performed by the optimizer, among which:
+  * Divisions and remainders by constants.
+  * Constant range checks of the form `x >= c1 && x <= c2`.
+
+For JavaScript:
+
+* Performance improvements for `Long`:
+  * They are not boxed anymore when stored in fields, stored in arrays, or passed as method arguments. They are still boxed when returned from methods.
+  * Division and remainder operations received a 3x speedup thanks to a new, state-of-the-art algorithm.
+
+For WebAssembly, performance improvements in the following areas:
+
+* `java.lang.Long.parseLong`, `parseUnsignedLong`.
+* Faster allocation of arrays of primitive types.
+* Fewer Wasm-to-JS calls for JavaScript methods that return primitive values.
+
+## Miscellaneous
+
+### New JDK APIs
+
+This release adds support for the following JDK methods:
+
+* In `java.lang.CharSequence`:
+  * `isEmpty`
+* In `java.lang.Math`:
+  * `scalb`
+* In `java.util.regex.Matcher`:
+  * `appendReplacement` and `appendTail` with a `StringBuilder` argument.
+  * `replaceFirst` and `replaceAll` with a `replacer: Function` argument.
+* In `java.lang.IndexOutOfBoundsException`:
+  * constructors with an `index` argument (`Int` or `Long`).
+
+## Bug fixes
+
+The following bugs have been fixed in 1.20.2:
+
+* [#5287](https://github.com/scala-js/scala-js/issues/5287) `MatchError.getMessage()` requires `getClass()`, which JS classes do not provide.
+* [#5246](https://github.com/scala-js/scala-js/issues/5246) Optimizer crash with Labeled+Return of inline class, discarded in statement position.
+* [#5180](https://github.com/scala-js/scala-js/issues/5180) Rare `AssertionError` when linking a corrupted codebase with a cyclic inheritance chain.
+
+You can find the full list [on GitHub](https://github.com/scala-js/scala-js/issues?q=is%3Aissue+milestone%3Av1.20.2+is%3Aclosed).

doc/all-api.md

@@ -5,6 +5,16 @@ title: All previous versions of the Scala.js API
 
 ## All previous versions of the API
 
+### Scala.js 1.20.2
+* [1.20.2 scalajs-library]({{ site.production_url }}/api/scalajs-library/1.20.2/scala/scalajs/js/index.html)
+* [1.20.2 scalajs-test-interface]({{ site.production_url }}/api/scalajs-test-interface/1.20.2/)
+* [1.20.2 scalajs-javalib-intf]({{ site.production_url }}/api/scalajs-javalib-intf/1.20.2/)
+* [1.20.2 scalajs-ir]({{ site.production_url }}/api/scalajs-ir/1.20.2/org/scalajs/ir/index.html)
+* [1.20.2 scalajs-linker-interface]({{ site.production_url }}/api/scalajs-linker-interface/1.20.2/org/scalajs/linker/interface/index.html) ([Scala.js version]({{ site.production_url }}/api/scalajs-linker-interface-js/1.20.2/org/scalajs/linker/interface/index.html))
+* [1.20.2 scalajs-linker]({{ site.production_url }}/api/scalajs-linker/1.20.2/org/scalajs/linker/index.html) ([Scala.js version]({{ site.production_url }}/api/scalajs-linker-js/1.20.2/org/scalajs/linker/index.html))
+* [1.20.2 scalajs-test-adapter]({{ site.production_url }}/api/scalajs-sbt-test-adapter/1.20.2/org/scalajs/testing/adapter/index.html)
+* [1.20.2 sbt-scalajs]({{ site.production_url }}/api/sbt-scalajs/1.20.2/#org.scalajs.sbtplugin.package)
+
 ### Scala.js 1.20.1
 * [1.20.1 scalajs-library]({{ site.production_url }}/api/scalajs-library/1.20.1/scala/scalajs/js/index.html)
 * [1.20.1 scalajs-test-interface]({{ site.production_url }}/api/scalajs-test-interface/1.20.1/)

doc/internals/version-history.md

@@ -5,6 +5,7 @@ title: Version history
 
 ## Version history of Scala.js
 
+- [1.20.2](/news/2026/01/05/announcing-scalajs-1.20.2/)
 - [1.20.1](/news/2025/09/06/announcing-scalajs-1.20.1/)
 - ~~1.20.0~~ ([severely broken](https://github.com/scala-js/scala-js/issues/5231) and therefore never announced)
 - [1.19.0](/news/2025/04/21/announcing-scalajs-1.19.0/)