On setups where python.executable property is not available infer jyt…

…hon executable path from sys.prefix #2441

The executable may not exists and it us up to the user to expose a wrapper if needed.

--HG--
extra : rebase_source : 975f01d2546ae2db43c2c2029dac2741001f0c91

src/org/python/core/PySystemState.java

@@ -1148,16 +1148,26 @@ private static PyList initArgv(String[] args) {
     }
 
     /**
-     * Determine the default sys.executable value from the registry. Returns Py.None is no
-     * executable can be found.
+     * Determine the default sys.executable value from the registry.
+     * If registry is not set (as in standalone jython jar), will use sys.prefix + /bin/jython(.exe) and the file may
+     * not exist. Users can create a wrapper in it's place to make it work in embedded environments.
+     * Only if sys.prefix is null, returns Py.None
      *
      * @param props a Properties registry
      * @return a PyObject path string or Py.None
      */
     private static PyObject initExecutable(Properties props) {
         String executable = props.getProperty("python.executable");
         if (executable == null) {
-            return Py.None;
+            if (prefix == null) {
+                return Py.None;
+            } else {
+                if (Platform.IS_WINDOWS) {
+                    executable = prefix.asString() + "/bin/jython.exe";
+                } else {
+                    executable = prefix.asString() + "/bin/jython";
+                }
+            }
         }
 
         File executableFile = new File(executable);
@@ -1166,9 +1176,6 @@ private static PyObject initExecutable(Properties props) {
         } catch (IOException ioe) {
             executableFile = executableFile.getAbsoluteFile();
         }
-        if (!executableFile.isFile()) {
-            return Py.None;
-        }
         return new PyString(executableFile.getPath());
     }