allow setting the sys.executable via an expert option

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/SysModuleBuiltins.java

@@ -112,7 +112,11 @@ public void initialize(PythonCore core) {
         builtinConstants.put("byteorder", ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN ? "little" : "big");
         builtinConstants.put("copyright", LICENSE);
         builtinConstants.put("dont_write_bytecode", true);
-        if (TruffleOptions.AOT || !core.getContext().isExecutableAccessAllowed()) {
+
+        String executable = PythonOptions.getOption(core.getContext(), PythonOptions.ExecutablePath);
+        if (!executable.isEmpty() && core.getContext().isExecutableAccessAllowed()) {
+            builtinConstants.put("executable", executable);
+        } else if (TruffleOptions.AOT || !core.getContext().isExecutableAccessAllowed()) {
             // cannot set the path at this time since the binary is not yet known; will be patched
             // in the context
             builtinConstants.put("executable", PNone.NONE);
@@ -140,6 +144,7 @@ public void initialize(PythonCore core) {
             builtinConstants.put("executable", sb.toString());
             builtinConstants.put("executable_list", core.factory().createList(exec_list.toArray()));
         }
+
         builtinConstants.put("modules", core.factory().createDict());
         builtinConstants.put("path", core.factory().createList());
         builtinConstants.put("builtin_module_names", core.factory().createTuple(core.builtinModuleNames()));

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PythonContext.java

@@ -41,6 +41,7 @@
 import org.graalvm.options.OptionValues;
 
 import com.oracle.graal.python.PythonLanguage;
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.builtins.objects.bytes.OpaqueBytes;
 import com.oracle.graal.python.builtins.objects.cext.NativeWrappers.PThreadState;
 import com.oracle.graal.python.builtins.objects.common.HashingStorage;
@@ -237,7 +238,9 @@ public void patch(Env newEnv) {
     private void setupRuntimeInformation() {
         PythonModule sysModule = core.initializeSysModule();
         if (ImageInfo.inImageRuntimeCode() && isExecutableAccessAllowed()) {
-            sysModule.setAttribute("executable", ProcessProperties.getExecutableName());
+            if (sysModule.getAttribute("executable") == PNone.NONE) {
+                sysModule.setAttribute("executable", ProcessProperties.getExecutableName());
+            }
         }
         sysModules = (PDict) sysModule.getAttribute("modules");
         builtinsModule = (PythonModule) sysModules.getItem("builtins");

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PythonOptions.java

@@ -128,6 +128,9 @@ private PythonOptions() {
     @Option(category = OptionCategory.EXPERT, help = "Set by the launcher to the terminal height.") //
     public static final OptionKey<Integer> TerminalHeight = new OptionKey<>(25);
 
+    @Option(category = OptionCategory.EXPERT, help = "The sys.executable path") //
+    public static final OptionKey<String> ExecutablePath = new OptionKey<>("");
+
     public static OptionDescriptors createDescriptors() {
         return new PythonOptionsOptionDescriptors();
     }