[2.x] fix: Propagate SBT_OPTS to BSP config (#8531)

Fixes #7469

When running 'sbt bspConfig', the generated .bsp/sbt.json now includes
JVM options from the SBT_OPTS environment variable. This ensures that
options like -Dsbt.boot.directory are propagated to the BSP server.

The parseSbtOpts method extracts -D, -X, and -J prefixed options from
SBT_OPTS and includes them in the BSP connection argv.

protocol/src/main/scala/sbt/internal/bsp/BuildServerConnection.scala

@@ -33,11 +33,8 @@ object BuildServerConnection {
       .orElse(sbtScriptInPath)
       .map(script => s"-Dsbt.script=$script")
 
-    // IntelliJ can start sbt even if the sbt script is not accessible from $PATH.
-    // To do so it uses its own bundled sbt-launch.jar.
-    // In that case, we must pass the path of the sbt-launch.jar to the BSP connection
-    // so that the server can be started.
-    // A known problem in that situation is that the .sbtopts and .jvmopts are not loaded.
+    val sbtOptsArgs = parseSbtOpts(sys.env.get("SBT_OPTS"))
+
     val sbtLaunchJar = classPath
       .split(File.pathSeparator)
       .find(jar => SbtLaunchJar.findFirstIn(jar).nonEmpty)
@@ -49,9 +46,12 @@ object BuildServerConnection {
         s"$javaHome/bin/java",
         "-Xms100m",
         "-Xmx100m",
-        "-classpath",
-        classPath,
       ) ++
+        sbtOptsArgs ++
+        Vector(
+          "-classpath",
+          classPath,
+        ) ++
         sbtScript ++
         Vector("xsbt.boot.Boot", "-bsp") ++
         (if (sbtScript.isEmpty) sbtLaunchJar else None)
@@ -62,8 +62,6 @@ object BuildServerConnection {
   }
 
   private def sbtScriptInPath: Option[String] = {
-    // For those who use an old sbt script, the -Dsbt.script is not set
-    // As a fallback we try to find the sbt script in $PATH
     val fileName = if (Properties.isWin) "sbt.bat" else "sbt"
     val envPath = sys.env.collectFirst {
       case (k, v) if k.toUpperCase() == "PATH" => v
@@ -76,4 +74,14 @@ object BuildServerConnection {
       .find(file => Files.exists(file) && Files.isExecutable(file))
       .map(_.toString.replace(" ", "%20"))
   }
+
+  private[sbt] def parseSbtOpts(sbtOpts: Option[String]): Vector[String] =
+    sbtOpts match
+      case Some(opts) if opts.nonEmpty =>
+        opts
+          .split("\\s+")
+          .filter(arg => arg.startsWith("-D") || arg.startsWith("-X") || arg.startsWith("-J"))
+          .map(arg => if (arg.startsWith("-J")) arg.stripPrefix("-J") else arg)
+          .toVector
+      case _ => Vector.empty
 }

protocol/src/test/scala/sbt/internal/bsp/BuildServerConnectionSpec.scala

@@ -0,0 +1,47 @@
+/*
+ * sbt
+ * Copyright 2023, Scala center
+ * Copyright 2011 - 2022, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt.internal.bsp
+
+import verify.BasicTestSuite
+
+object BuildServerConnectionSpec extends BasicTestSuite:
+
+  test("parseSbtOpts should return empty vector for None"):
+    val result = BuildServerConnection.parseSbtOpts(None)
+    assert(result.isEmpty)
+
+  test("parseSbtOpts should return empty vector for empty string"):
+    val result = BuildServerConnection.parseSbtOpts(Some(""))
+    assert(result.isEmpty)
+
+  test("parseSbtOpts should parse -D system properties"):
+    val result = BuildServerConnection.parseSbtOpts(Some("-Dsbt.boot.directory=/custom/path"))
+    assert(result == Vector("-Dsbt.boot.directory=/custom/path"))
+
+  test("parseSbtOpts should parse -X JVM options"):
+    val result = BuildServerConnection.parseSbtOpts(Some("-Xmx2g -Xms512m"))
+    assert(result == Vector("-Xmx2g", "-Xms512m"))
+
+  test("parseSbtOpts should parse -J prefixed options and strip the prefix"):
+    val result = BuildServerConnection.parseSbtOpts(Some("-J-Xmx4g"))
+    assert(result == Vector("-Xmx4g"))
+
+  test("parseSbtOpts should parse multiple mixed options"):
+    val result = BuildServerConnection.parseSbtOpts(
+      Some("-Dsbt.boot.directory=/path -Xmx2g -J-XX:+UseG1GC")
+    )
+    assert(result == Vector("-Dsbt.boot.directory=/path", "-Xmx2g", "-XX:+UseG1GC"))
+
+  test("parseSbtOpts should filter out non-JVM options"):
+    val result = BuildServerConnection.parseSbtOpts(Some("-Dfoo=bar --some-flag -Xmx1g"))
+    assert(result == Vector("-Dfoo=bar", "-Xmx1g"))
+
+  test("parseSbtOpts should handle whitespace-separated options"):
+    val result = BuildServerConnection.parseSbtOpts(Some("  -Dfoo=bar   -Xmx1g  "))
+    assert(result == Vector("-Dfoo=bar", "-Xmx1g"))