Treat foreign executables as builtins which allows them to have __text_signature__

Author: timfel

CHANGELOG.md

@@ -5,6 +5,7 @@ language runtime. The main focus is on user-observable behavior of the engine.
 
 ## Version 25.0.0
 * `dir(foreign_object)` now returns both foreign methods and Python methods (it used to return only foreign methods).
+* Support `__name__`, `__doc__`, `__text_signature__` fields on foreign executables to serve as their proper counterparts on the Python side. This is useful to, for example, use Java functional interfaces in lieu of Python functions for things like LangChain's `@tool` annotation that want to inspect the underlying function.
 
 ## Version 24.2.0
 * Updated developer metadata of Maven artifacts.

graalpython/com.oracle.graal.python.test.integration/src/com/oracle/graal/python/test/integration/interop/JavaInteropTest.java

@@ -839,6 +839,46 @@ class Bar(Foo):
             assertEquals(object.getMetaSimpleName(), "object");
             assertFalse(object.hasMetaParents());
         }
+
+        public static class MyFunction implements java.util.function.Function<String, String> {
+            public String __text_signature__ = "(string) -> str";
+
+            @Override
+            public String apply(String s) {
+                return s;
+            }
+        }
+
+        public static class MyFunctionWithCustomName implements java.util.function.Function<String, String> {
+            public String __text_signature__ = "(string) -> str";
+            public String __name__ = "myfunc";
+
+            @Override
+            public String apply(String s) {
+                return s;
+            }
+        }
+
+        public static class MyFunctionWithIncorrectSignature implements java.util.function.Function<String, String> {
+            public String __text_signature__ = "[I;java.lang.String;";
+
+            @Override
+            public String apply(String s) {
+                return s;
+            }
+        }
+
+        @Test
+        public void javaExecutablesAsPythonFunctions() throws IOException {
+            Value inspectSignature = context.eval("python", "import inspect; inspect.signature");
+            assertEquals("<Signature (string)>", inspectSignature.execute(new MyFunction()).toString());
+
+            Value signature = context.eval("python", "lambda f: f.__text_signature__");
+            assertEquals(new MyFunctionWithIncorrectSignature().__text_signature__, signature.execute(new MyFunctionWithIncorrectSignature()).asString());
+
+            Value name = context.eval("python", "lambda f: f.__name__");
+            assertEquals(new MyFunctionWithCustomName().__name__, name.execute(new MyFunctionWithCustomName()).asString());
+        }
     }
 
     @RunWith(Parameterized.class)

graalpython/lib-python/3/inspect.py

@@ -2069,6 +2069,9 @@ def _signature_is_builtin(obj):
     return (isbuiltin(obj) or
             ismethoddescriptor(obj) or
             isinstance(obj, _NonUserDefinedCallables) or
+            # Truffle change: treat foreign executables as builtin
+            (isinstance(obj, __graalpython__.ForeignType) and callable(obj)) or
+            # End Truffle change
             # Can't test 'isinstance(type)' here, as it would
             # also be True for regular python classes
             obj in (type, object))