Add library.properties to resources of scala-library jars

library/src/scala/util/Properties.scala

@@ -34,6 +34,7 @@ private[scala] trait PropertiesTrait {
 
   /** The name of the properties file */
   protected val propFilename = "/" + propCategory + ".properties"
+  protected val lib3Filename = "/library3.properties"
 
   /** The loaded properties */
   protected lazy val scalaProps: java.util.Properties = {
@@ -42,6 +43,12 @@ private[scala] trait PropertiesTrait {
     if (stream ne null)
       quietlyDispose(props.load(stream), stream.close)
 
+    // If available in the same jar as the stdlib classes, overlay Scala 3
+    // runtime properties contained in `library3.properties` (e.g., version.number).
+    val lib3Stream = pickJarBasedOn.getResourceAsStream(lib3Filename)
+    if (lib3Stream ne null)
+      quietlyDispose(props.load(lib3Stream), lib3Stream.close)
+
     props
   }
 

project/Build.scala

@@ -1916,6 +1916,19 @@ object Build {
       customMimaReportBinaryIssues("MiMaFilters.Scala3Library"),
       // Should we also patch .sjsir files
       keepSJSIR := false,
+      Compile / resourceGenerators += Def.task {
+        val file = (Compile / resourceManaged).value / "library3.properties"
+        val contents =
+          s"""version.number=${version.value}
+             |maven.version.number=${version.value}
+             |""".stripMargin
+
+        if (!(file.exists && IO.read(file) == contents)) {
+          IO.write(file, contents)
+        }
+
+        Seq(file)
+      }.taskValue,
     )
 
   /* Configuration of the org.scala-lang:scala3-library_3:*.**.**-nonbootstrapped project */
@@ -2041,6 +2054,19 @@ object Build {
       customMimaReportBinaryIssues("MiMaFilters.Scala3Library"),
       // Should we also patch .sjsir files
       keepSJSIR := false,
+      Compile / resourceGenerators += Def.task {
+        val file = (Compile / resourceManaged).value / "library3.properties"
+        val contents =
+          s"""version.number=${version.value}
+             |maven.version.number=${version.value}
+             |""".stripMargin
+
+        if (!(file.exists && IO.read(file) == contents)) {
+          IO.write(file, contents)
+        }
+
+        Seq(file)
+      }.taskValue,
     )
 
   /* Configuration of the org.scala-lang:scala3-library_3:*.**.**-bootstrapped project */

tests/run/properties-version-string.check

@@ -0,0 +1 @@
+OK

tests/run/properties-version-string.scala

@@ -0,0 +1,7 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    val v = scala.util.Properties.versionNumberString
+    if (v.nonEmpty && !v.startsWith("2.")) println("OK")
+    else println("FAIL " + v)
+  }
+}