Fix $callable hidden kwargs leaking into signatures

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/function/AbstractFunctionBuiltins.java

@@ -308,7 +308,7 @@ static TruffleString getBuiltin(PBuiltinFunction self, @SuppressWarnings("unused
 
         @TruffleBoundary
         public static TruffleString signatureToText(Signature signature, boolean skipSelf) {
-            TruffleString[] keywordNames = signature.getKeywordNames();
+            TruffleString[] keywordNames = signature.getVisibleKeywordNames();
             boolean takesVarArgs = signature.takesVarArgs();
             boolean takesVarKeywordArgs = signature.takesVarKeywordArgs();
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/function/BuiltinFunctionBuiltins.java

@@ -172,7 +172,7 @@ public static Object createInspectSignagure(Signature signature, boolean skipSel
             Object inspectParameter = PyObjectGetAttr.executeUncached(inspect, tsLiteral("Parameter"));
             Object[] parameterKinds = new Object[ParameterKinds.VALUES.length];
 
-            TruffleString[] keywordNames = signature.getKeywordNames();
+            TruffleString[] keywordNames = signature.getVisibleKeywordNames();
             boolean takesVarArgs = signature.takesVarArgs();
             boolean takesVarKeywordArgs = signature.takesVarKeywordArgs();
             TruffleString[] parameterNames = signature.getParameterIds();

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/function/Signature.java

@@ -27,9 +27,14 @@
 
 import static com.oracle.graal.python.nodes.BuiltinNames.T_SELF;
 import static com.oracle.graal.python.nodes.StringLiterals.T_EMPTY_STRING;
+import static com.oracle.graal.python.util.PythonUtils.TS_ENCODING;
+
+import java.util.ArrayList;
+import java.util.List;
 
 import com.oracle.graal.python.util.PythonUtils;
 import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
+import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.strings.TruffleString;
 
 public final class Signature {
@@ -127,6 +132,21 @@ public final TruffleString[] getKeywordNames() {
         return keywordOnlyNames;
     }
 
+    @TruffleBoundary
+    public TruffleString[] getVisibleKeywordNames() {
+        /*
+         * C slot wrappers (ab)use keyword defaults for storing the function pointers, we need to
+         * filter them out. Their names start with a dollar sign.
+         */
+        List<TruffleString> visibleKeywordNames = new ArrayList<>(keywordOnlyNames.length);
+        for (TruffleString k : keywordOnlyNames) {
+            if (k.byteLength(TS_ENCODING) > 0 && k.codePointAtByteIndexUncached(0, TS_ENCODING) != '$') {
+                visibleKeywordNames.add(k);
+            }
+        }
+        return visibleKeywordNames.toArray(TruffleString[]::new);
+    }
+
     public final boolean takesKeywordArgs() {
         return keywordOnlyNames.length > 0 || takesVarKeywordArgs;
     }