add java.add_to_classpath API

Author: timfel

CHANGELOG.md

@@ -3,6 +3,10 @@
 This changelog summarizes major changes between GraalVM versions of the Python
 language runtime. The main focus is on user-observable behavior of the engine.
 
+## Version 20.0.0 beta 2
+
+* Add `java.add_to_classpath` API to dynamically extend the host class path
+
 ## Version 20.0.0 beta 1
 
 * Update Python standard library files to Python 3.7.3

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

@@ -48,17 +48,22 @@
 import com.oracle.graal.python.builtins.Builtin;
 import com.oracle.graal.python.builtins.CoreFunctions;
 import com.oracle.graal.python.builtins.PythonBuiltins;
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.builtins.objects.str.PString;
 import com.oracle.graal.python.nodes.function.PythonBuiltinBaseNode;
+import com.oracle.graal.python.nodes.function.PythonBuiltinNode;
 import com.oracle.graal.python.nodes.function.builtins.PythonBinaryBuiltinNode;
 import com.oracle.graal.python.nodes.function.builtins.PythonUnaryBuiltinNode;
+import com.oracle.graal.python.nodes.util.CastToStringNode;
 import com.oracle.graal.python.runtime.PythonCore;
 import com.oracle.graal.python.runtime.exception.PythonErrorType;
 import com.oracle.truffle.api.TruffleLanguage.Env;
+import com.oracle.truffle.api.dsl.Cached;
 import com.oracle.truffle.api.dsl.Fallback;
 import com.oracle.truffle.api.dsl.GenerateNodeFactory;
 import com.oracle.truffle.api.dsl.NodeFactory;
 import com.oracle.truffle.api.dsl.Specialization;
+import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.interop.TruffleObject;
 
 @CoreFunctions(defineModule = "java")
@@ -106,6 +111,25 @@ Object type(PString name) {
         }
     }
 
+    @Builtin(name = "add_to_classpath", takesVarArgs = true)
+    @GenerateNodeFactory
+    abstract static class AddToClassPathNode extends PythonBuiltinNode {
+        @Specialization
+        PNone add(VirtualFrame frame, Object[] args,
+                  @Cached CastToStringNode castToString) {
+            Env env = getContext().getEnv();
+            for (Object arg : args) {
+                String entry = castToString.execute(frame, arg);
+                try {
+                    env.addToHostClassPath(env.getTruffleFile(entry));
+                } catch (SecurityException e) {
+                    throw raise(TypeError, "invalid or unreadable classpath: '%s' - %m", entry, e);
+                }
+            }
+            return PNone.NONE;
+        }
+    }
+
     @Builtin(name = "is_function", minNumOfPositionalArgs = 1)
     @GenerateNodeFactory
     abstract static class IsFunctionNode extends PythonUnaryBuiltinNode {