Fix BSP install argv path (#5061)

Fixes #5058

It seems the `mill.main.cli` property and `MILL_MAIN_CLI` environment
variable were not getting propagated properly, and the server-side
`java.class.path` property we were falling back to is now invalid since
#5025.

The solution is to propagate a single `MILL_EXECUTABLE_PATH` variable
computed from `class
.getProtectionDomain().getCodeSource().getLocation()`, which returns the
assembly jar in `packaged` on or native binary in `native` mode. This
doesn't work in `local` mode, but that's fine since the `.ide` tests
don't pass in `local` mode anyway.

As we now handle `MILL_EXECUTABLE_PATH` in a narrow code path from the
Mill launcher to the Mill server, we no longer need special handling in
all the Mill bootstrap scripts to pass in this variable

Added a test case to `ide[bsp-modules]` to exercise this at least on the
JVM; tested the native image case manually. Also tested the JVM launcher
in intellij via `MILL_STABLE_VERSION=1 ./mill dist.installLocalCache`
and verified the BSP import no longer immediately crashes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: lihaoyi

ci/mill.ps1

@@ -122,7 +122,7 @@ if (-not (Test-Path -Path $MILL -PathType Leaf)) {
     Invoke-WebRequest -Uri $DOWNLOAD_URL -OutFile $MILL
 }
 
-$MILL_MAIN_CLI = $Env:MILL_MAIN_CLI ?? $PSCommandPath
+
 
 $MILL_FIRST_ARG = $null
 $REMAINING_ARGUMENTS = $remainingArgs
@@ -134,4 +134,4 @@ if ($null -ne $remainingArgs) {
     }
 }
 
-& $MILL $MILL_FIRST_ARG -D "mill.main.cli=$MILL_MAIN_CLI" $REMAINING_ARGUMENTS
+& $MILL $MILL_FIRST_ARG $REMAINING_ARGUMENTS

core/constants/src/mill/constants/EnvVars.java

@@ -42,4 +42,9 @@ public class EnvVars {
    * e.g. to turn on additional testing/debug/log-related code
    */
   public static final String MILL_TEST_SUITE = "MILL_TEST_SUITE";
+
+  /**
+   * The path to the currently executing Mill launcher executable
+   */
+  public static final String MILL_EXECUTABLE_PATH = "MILL_EXECUTABLE_PATH";
 }

integration/feature/subprocess-stdout/resources/mill

@@ -31,3 +31,7 @@ def validate() = Task.Command {
   os.write(file, content)
   PathRef(file)
 }
+
+def checkExecutable() = Task.Command {
+  println("checkExecutable succeeded")
+}

integration/ide/bsp-modules/resources/build.mill

@@ -14,6 +14,15 @@ object BspModulesTests extends UtestIntegrationTestSuite {
         val res = eval("mill.bsp.BSP/install")
         assert(res.isSuccess)
         os.exists(workspacePath / Constants.bspDir / s"${Constants.serverName}.json") ==> true
+        val json = ujson.read(
+          os.read(workspacePath / Constants.bspDir / s"${Constants.serverName}.json")
+        )
+
+        val executable = json("argv").arr(0).str
+        val checkRes = os.call((executable, "checkExecutable"), cwd = workspacePath)
+        assert(checkRes.exitCode == 0)
+        assert(checkRes.out.text().contains("checkExecutable succeeded"))
+        ()
       }
       test("ModuleUtils resolves all referenced transitive modules") - integrationTest { tester =>
         import tester._

integration/ide/bsp-modules/src/BspModulesTests.scala

@@ -43,7 +43,7 @@ object BspServerTests extends UtestIntegrationTestSuite {
         stdout = os.Inherit,
         stderr = os.Inherit,
         check = true,
-        env = Map("MILL_MAIN_CLI" -> tester.millExecutable.toString)
+        env = Map("MILL_EXECUTABLE_PATH" -> tester.millExecutable.toString)
       )
 
       withBspServer(

integration/ide/bsp-server/src/BspServerTests.scala

@@ -294,10 +294,6 @@ if [ ! -s "${MILL}" ] ; then
   fi
 fi
 
-if [ -z "$MILL_MAIN_CLI" ] ; then
-  MILL_MAIN_CLI="${0}"
-fi
-
 MILL_FIRST_ARG=""
 if [ "$1" = "--bsp" ] || [ "$1" = "-i" ] || [ "$1" = "--interactive" ] || [ "$1" = "--no-server" ] || [ "$1" = "--repl" ] || [ "$1" = "--help" ] ; then
   # Need to preserve the first position of those listed options
@@ -313,4 +309,4 @@ unset MILL_REPO_URL
 
 # We don't quote MILL_FIRST_ARG on purpose, so we can expand the empty value without quotes
 # shellcheck disable=SC2086
-exec "${MILL}" $MILL_FIRST_ARG -D "mill.main.cli=${MILL_MAIN_CLI}" "$@"
+exec "${MILL}" $MILL_FIRST_ARG "$@"

mill

@@ -42,9 +42,6 @@ if [!GITHUB_RELEASE_CDN!]==[] (
     set "GITHUB_RELEASE_CDN="
 )
 
-if [!MILL_MAIN_CLI!]==[] (
-    set "MILL_MAIN_CLI=%~f0"
-)
 
 set "MILL_REPO_URL=https://github.com/com-lihaoyi/mill"
 
@@ -267,4 +264,4 @@ if not [!MILL_FIRST_ARG!]==[] (
   )
 )
 
-"%MILL%" %MILL_FIRST_ARG% -D "mill.main.cli=%MILL_MAIN_CLI%" %MILL_PARAMS%
+"%MILL%" %MILL_FIRST_ARG%  %MILL_PARAMS%

mill.bat

@@ -34,11 +34,8 @@ private[mill] object BSP {
   }
 
   private def bspConnectionJson(jobs: Int, debug: Boolean): String = {
-    val millPath = sys.env.get("MILL_MAIN_CLI")
-      .orElse(sys.props.get("mill.main.cli"))
-      // we assume, the classpath is an executable jar here
-      .orElse(sys.props.get("java.class.path"))
-      .getOrElse(throw new IllegalStateException("System property 'java.class.path' not set"))
+    val millPath = sys.env.get("MILL_EXECUTABLE_PATH")
+      .getOrElse(throw new IllegalStateException("Env 'MILL_EXECUTABLE_PATH' not set"))
 
     upickle.default.write(
       BspConfigJson(

runner/bsp/src/mill/bsp/BSP.scala

@@ -76,6 +76,7 @@ static Process configureRunMillProcess(ProcessBuilder builder, Path serverDir) t
     Path sandbox = serverDir.resolve(ServerFiles.sandbox);
     Files.createDirectories(sandbox);
     builder.environment().put(EnvVars.MILL_WORKSPACE_ROOT, new File("").getCanonicalPath());
+    builder.environment().put(EnvVars.MILL_EXECUTABLE_PATH, getExecutablePath());
 
     String jdkJavaOptions = System.getenv("JDK_JAVA_OPTIONS");
     if (jdkJavaOptions == null) jdkJavaOptions = "";
@@ -386,4 +387,20 @@ public static void prepareMillRunFolder(Path serverDir) throws Exception {
     termInfoPropagatorThread.setDaemon(true);
     termInfoPropagatorThread.start();
   }
+
+  public static String getExecutablePath() {
+    try {
+      // Gets the location of the JAR or native image
+      Path path = Paths.get(MillProcessLauncher.class
+          .getProtectionDomain()
+          .getCodeSource()
+          .getLocation()
+          .toURI());
+
+      File file = path.toFile();
+      return file.getAbsolutePath();
+    } catch (java.net.URISyntaxException e) {
+      throw new RuntimeException("Failed to determine Mill client executable path", e);
+    }
+  }
 }