升级Scala2.12到Scala3
王福强
2024-06-02
今天尝试把自己的Scala2.12的一个项目UtilitiesFX升级成Scala3,看看有多大难度。
升级思路大体上是:
- 整体复制项目目录到新的目的,并将目录重新命名(以视觉上区分);
- 将新项目的artifact名称改掉,追加
-scala3
,以从依赖管理层面区分; - 更改maven中scala相关依赖与配置,主要是scala版本号更改以及scala-library依赖的更改。
plugin>
<<!--http://davidb.github.io/scala-maven-plugin/usage.html-->
groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
<version>${scala.plugin.version}</version>
<plugin>
</
...<!-- https://mvnrepository.com/artifact/org.scala-lang/scala3-library -->
dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala3-library_3</artifactId>
<version>3.4.2</version>
<dependency>
</ ...
另外就是,把所有_2.12
到依赖也都要改成_3
,比如:
dependency>
<groupId>com.lihaoyi</groupId>
<artifactId>requests_3</artifactId>
<version>0.8.3</version>
<dependency> </
下面是遇到的一些错误与警告,看起来broken的地方不多,大部分是warnings
Brokens
Unit方法也必须=
[ERROR] [Error] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/utils/CartesianProduct.scala:84:62: '=' expected, but '{' found
[ERROR] [Error] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/utils/CartesianProduct.scala:92:32: '=' expected, but '{' found
类型转换更严格
[ERROR] [Error] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/utils/AnchorPanes.scala:35:36: Found: (gap : Int)
Required: Double
方法调用更严格
[ERROR] [Error] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/utils/Images.scala:141:154: method pasteFromClipboard in object Images must be called with () argument
() => pasteFromClipboard.foreach(imageProperty.set(_))
-> () => pasteFromClipboard().foreach(imageProperty.set(_))
WARNINGS
var args展开
从var:_*
-> var*
类型定义与约束中的通配符_
从_
变成?
,比如
T[ _<:S ]
变成T[ ?<:S ]
task: Worker[_]
->task: Worker[?]
() => pasteFromClipboard.foreach(imageProperty.set(_))
->() => pasteFromClipboard().foreach(imageProperty.set(_))
// 这里是方法调用的括号不能省略(否则认为是方法引用了,相当于加强了约束), 通配符反而可以继续用
变量通配符
从var splashScreen: Stage = _
变成var splashScreen: Stage = uninitialized
(而且还得import scala.compiletime.uninitialized)
我觉得tmd这是倒退,我宁愿null
集合类型转换
[WARNING] [Warn] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/controls/launchctl/LaunchControlBlocks.scala:19:24: object JavaConverters in package scala.collection is deprecated since 2.13.0: Use `scala.jdk.CollectionConverters` instead
数据类型转换
[WARNING] [Warn] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/javafx/utils/TextInputControlTyper.scala:11:41: method long2double in object Long is deprecated since 2.13.1: Implicit conversion from Long to Double is dangerous because it loses precision. Write `.toDouble` instead.
linestream到lazylines
[WARNING] [Warn] /Users/fq/workspace.scala3/UtilitiesFX-scala3/src/main/scala/com/keevol/utils/CommandRunner.scala:50:49: method lineStream_! in trait ProcessBuilder is deprecated since 2.13.0: use lazyLines_!
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