Add apis to discard extra arguments when calling Python functions

src/core/pyproxy.ts

@@ -2347,7 +2347,7 @@ export class PyCallableMethods {
     return Module.callPyObject(_getPtr(this), jsargs);
   }
   /**
-   * Call the function with key word arguments. The last argument must be an
+   * Call the function with keyword arguments. The last argument must be an
    * object with the keyword arguments.
    */
   callKwargs(...jsargs: any) {
@@ -2366,6 +2366,38 @@ export class PyCallableMethods {
     return Module.callPyObjectKwargs(_getPtr(this), jsargs, kwargs);
   }
 
+  /**
+   * Call the function in a "relaxed" manner. Any extra arguments will be
+   * ignored. This matches the behavior of JavaScript functions more accurately.
+   *
+   * Any extra arguments will be ignored. This matches the behavior of
+   * JavaScript functions more accurately. Missing arguments are **NOT** filled
+   * with `None`. If too few arguments are passed, this will still raise a
+   * TypeError.
+   *
+   * This uses :py:func:`pyodide.code.relaxed_call`.
+   */
+  callRelaxed(...jsargs: any) {
+    return API.pyodide_code.relaxed_call(this, ...jsargs);
+  }
+
+  /**
+   * Call the function with keyword arguments in a "relaxed" manner. The last
+   * argument must be an object with the keyword arguments. Any extra arguments
+   * will be ignored. This matches the behavior of JavaScript functions more
+   * accurately.
+   *
+   * Missing arguments are **NOT** filled with `None`. If too few arguments are
+   * passed, this will still raise a TypeError. Also, if the same argument is
+   * passed as both a keyword argument and a positional argument, it will raise
+   * an error.
+   *
+   * This uses :py:func:`pyodide.code.relaxed_call`.
+   */
+  callKwargsRelaxed(...jsargs: any) {
+    return API.pyodide_code.relaxed_call.callKwargs(this, ...jsargs);
+  }
+
   /**
    * Call the function with stack switching enabled. Functions called this way
    * can use

src/py/pyodide/code.py

@@ -1,3 +1,4 @@
+from functools import lru_cache
 from typing import Any
 
 from _pyodide._base import (
@@ -25,11 +26,57 @@ def run_js(code: str, /) -> Any:
     return eval_(code)
 
 
+@lru_cache
+def _relaxed_call_sig(func):
+    from inspect import Parameter, signature
+
+    try:
+        sig = signature(func)
+    except (TypeError, ValueError):
+        return None
+    new_params = list(sig.parameters.values())
+    idx: int | None = -1
+    for idx, param in enumerate(new_params):
+        if param.kind in (Parameter.KEYWORD_ONLY, Parameter.VAR_KEYWORD):
+            break
+        if param.kind == Parameter.VAR_POSITIONAL:
+            idx = None
+            break
+    else:
+        idx += 1
+    if idx is not None:
+        new_params.insert(idx, Parameter("__var_positional", Parameter.VAR_POSITIONAL))
+
+    for param in new_params:
+        if param.kind == Parameter.KEYWORD_ONLY:
+            break
+    else:
+        new_params.append(Parameter("__var_keyword", Parameter.VAR_KEYWORD))
+    new_sig = sig.replace(parameters=new_params)
+    return new_sig
+
+
+def relaxed_call(func, *args, **kwargs):
+    """Call the function ignoring extra arguments
+
+    If extra positional or keyword arguments are provided they will be
+    discarded.
+    """
+    sig = _relaxed_call_sig(func)
+    if sig is None:
+        func(*args, **kwargs)
+    bound = sig.bind(*args, **kwargs)
+    bound.arguments.pop("__var_positional", None)
+    bound.arguments.pop("__var_keyword", None)
+    return func(*bound.args, **bound.kwargs)
+
+
 __all__ = [
     "CodeRunner",
     "eval_code",
     "eval_code_async",
     "find_imports",
     "should_quiet",
     "run_js",
+    "relaxed_call",
 ]