JRUBY-4834: Kernel.exec doesn't use modified ENV["PATH"] to locate co…

…mmands on Windows

One regression test added as well.

src/org/jruby/util/ShellLauncher.java

@@ -28,10 +28,12 @@
 
 package org.jruby.util;
 
+import static java.lang.System.out;
+
+import java.io.BufferedInputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
-import java.io.BufferedInputStream;
 import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -40,15 +42,14 @@
 import java.io.PipedOutputStream;
 import java.io.PrintStream;
 import java.lang.reflect.Field;
-import static java.lang.System.*;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
-import java.util.regex.Pattern;
 import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.jruby.Main;
 import org.jruby.Ruby;
@@ -330,7 +331,11 @@ private static File findPathFile(Ruby runtime, String fname, String[] path, bool
     }
 
     private static File findPathExecutable(Ruby runtime, String fname) {
-        String path = System.getenv(PATH_ENV);
+        RubyHash envHash = (RubyHash) runtime.getObject().fastGetConstant("ENV");
+        String path = envHash.op_aref(
+                runtime.getCurrentContext(),
+                runtime.newString(PATH_ENV)).asJavaString();
+
         String[] pathNodes = null;
         if (path == null) {
             pathNodes = DEFAULT_PATH; // ASSUME: not modified by callee

test/test_kernel.rb

@@ -502,6 +502,21 @@ def test_exec_non_existing_with_args
     }
   end
 
+  # JRUBY-4834
+  def test_backquote_with_changed_path
+    orig_env = ENV['PATH']
+
+    # Append a directory where testapp resides to the PATH
+    paths = (ENV["PATH"] || "").split(File::PATH_SEPARATOR)
+    paths.unshift TESTAPP_DIR
+    ENV["PATH"] = paths.uniq.join(File::PATH_SEPARATOR)
+
+    res = `testapp`.chomp
+    assert_equal("NO_ARGS", res)
+  ensure
+    ENV['PATH'] = orig_env
+  end
+
   # JRUBY-4127
   def test_backquote_with_quotes
     if (WINDOWS)