Fix #2881 Propagate environment from ctx to subprocesses

build.sc

@@ -374,6 +374,12 @@ trait MillBaseTestsModule extends MillJavaModule with TestModule {
     )
   }
 
+  def forkEnv = T {
+    super.forkEnv() ++ Seq(
+      "TEST_ENV_VARIABLE" -> "value"
+    )
+  }
+
   def testFramework = "mill.UTestFramework"
 }
 

main/util/src/mill/util/Jvm.scala

@@ -146,21 +146,46 @@ object Jvm extends CoursierSupport {
 
     ctx.log.debug(s"Run subprocess with args: ${args.map(a => s"'${a}'").mkString(" ")}")
 
+    val envWithPropagated = ctx.env ++ envArgs
+
     if (backgroundOutputs.nonEmpty)
-      spawnSubprocessWithBackgroundOutputs(args, envArgs, workingDir, backgroundOutputs)
+      spawnSubprocessWithBackgroundOutputs(
+        args,
+        envWithPropagated,
+        workingDir,
+        backgroundOutputs,
+        propagateEnv = false
+      )
     else
-      runSubprocess(args, envArgs, workingDir)
+      runSubprocess(args, envWithPropagated, workingDir, propagateEnv = false)
   }
 
   /**
    * Runs a generic subprocess and waits for it to terminate.
    */
-  def runSubprocess(commandArgs: Seq[String], envArgs: Map[String, String], workingDir: os.Path) = {
+  def runSubprocess(
+      commandArgs: Seq[String],
+      envArgs: Map[String, String],
+      workingDir: os.Path
+  ): Unit = runSubprocess(
+    commandArgs = commandArgs,
+    envArgs = envArgs,
+    workingDir = workingDir,
+    propagateEnv = true
+  )
+
+  private def runSubprocess(
+      commandArgs: Seq[String],
+      envArgs: Map[String, String],
+      workingDir: os.Path,
+      propagateEnv: Boolean
+  ): Unit = {
     val process = spawnSubprocessWithBackgroundOutputs(
       commandArgs,
       envArgs,
       workingDir,
-      backgroundOutputs = None
+      backgroundOutputs = None,
+      propagateEnv = propagateEnv
     )
     val shutdownHook = new Thread("subprocess-shutdown") {
       override def run(): Unit = {
@@ -217,6 +242,20 @@ object Jvm extends CoursierSupport {
       envArgs: Map[String, String],
       workingDir: os.Path,
       backgroundOutputs: Option[Tuple2[ProcessOutput, ProcessOutput]] = None
+  ): SubProcess = spawnSubprocessWithBackgroundOutputs(
+    commandArgs = commandArgs,
+    envArgs = envArgs,
+    workingDir = workingDir,
+    backgroundOutputs = backgroundOutputs,
+    propagateEnv = true
+  )
+
+  private def spawnSubprocessWithBackgroundOutputs(
+      commandArgs: Seq[String],
+      envArgs: Map[String, String],
+      workingDir: os.Path,
+      backgroundOutputs: Option[Tuple2[ProcessOutput, ProcessOutput]],
+      propagateEnv: Boolean
   ): SubProcess = {
     // If System.in is fake, then we pump output manually rather than relying
     // on `os.Inherit`. That is because `os.Inherit` does not follow changes
@@ -230,7 +269,8 @@ object Jvm extends CoursierSupport {
         env = envArgs,
         stdin = if (backgroundOutputs.isEmpty) os.Pipe else "",
         stdout = backgroundOutputs.map(_._1).getOrElse(os.Pipe),
-        stderr = backgroundOutputs.map(_._2).getOrElse(os.Pipe)
+        stderr = backgroundOutputs.map(_._2).getOrElse(os.Pipe),
+        propagateEnv = propagateEnv
       )
 
       val sources = Seq(
@@ -255,7 +295,8 @@ object Jvm extends CoursierSupport {
         env = envArgs,
         stdin = if (backgroundOutputs.isEmpty) os.Inherit else "",
         stdout = backgroundOutputs.map(_._1).getOrElse(os.Inherit),
-        stderr = backgroundOutputs.map(_._2).getOrElse(os.Inherit)
+        stderr = backgroundOutputs.map(_._2).getOrElse(os.Inherit),
+        propagateEnv = propagateEnv
       )
     }
   }

scalalib/test/resources/hello-world/env/src/Main.scala

@@ -0,0 +1,12 @@
+import java.nio.file.{Files, Paths}
+
+object Main {
+  def main(args: Array[String]): Unit = {
+    val resultPath = Paths.get(args(0))
+    Files.createDirectories(resultPath.getParent)
+    Files.write(
+      resultPath,
+      s"TEST_ENV_VARIABLE=${sys.env.getOrElse("TEST_ENV_VARIABLE", "")}".getBytes
+    )
+  }
+}

scalalib/test/src/mill/scalalib/HelloWorldTests.scala

@@ -382,6 +382,12 @@ object HelloWorldTests extends TestSuite {
     }
   }
 
+  object HelloWorldWithoutEnv extends HelloBase {
+    object env extends HelloWorldModule {
+      def forkEnv = T { Map.empty[String, String] }
+    }
+  }
+
   val resourcePath = os.pwd / "scalalib" / "test" / "resources" / "hello-world"
 
   def jarMainClass(jar: JarFile): Option[String] = {
@@ -810,6 +816,18 @@ object HelloWorldTests extends TestSuite {
         val Left(Result.Failure(_, None)) = eval.apply(HelloWorldWithoutMain.core.runLocal())
 
       }
+      "envIsPropagated" - workspaceTest(HelloWorldWithoutEnv) { eval =>
+        val runResult = eval.outPath / "env" / "run.dest" / "hello-mill"
+        val Right((_, evalCount)) =
+          eval.apply(HelloWorldWithoutEnv.env.run(T.task(Args(runResult.toString))))
+
+        assert(sys.env.get("TEST_ENV_VARIABLE") == Some("value"))
+        assert(evalCount > 0)
+        assert(os.exists(runResult))
+
+        val output = os.read(runResult)
+        assert(output == "TEST_ENV_VARIABLE=value")
+      }
     }
 
     "jar" - {