Method evalCall

src/main/java/net/starlark/java/eval/Eval.java:668–769

(StarlarkThread.Frame fr, CallExpression call)

  }

  private static Object evalCall(StarlarkThread.Frame fr, CallExpression call)
      throws EvalException, InterruptedException {
    fr.thread.checkInterrupt();

    Object fn = eval(fr, call.getFunction());

    // Starlark arguments are ordered: positionals < keywords < *args < **kwargs.
    //
    // This is stricter than Python2, which doesn't constrain keywords wrt *args,
    // but this ensures that the effects of evaluation of Starlark arguments occur
    // in source order.
    //
    // Starlark does not support Python3's multiple *args and **kwargs
    // nor freer ordering, such as f(a, *list, *list, **dict, **dict, b=1).
    // Supporting it would complicate a compiler, and produce effects out of order.
    // Also, Python's argument ordering rules are complex and the errors sometimes cryptic.

    // StarStar and Star args are guaranteed to be last, if they occur.
    ImmutableList<Argument> arguments = call.getArguments();
    int numNonStarArgs = arguments.size();
    Argument.StarStar starstar = null;
    if (numNonStarArgs > 0 && arguments.get(numNonStarArgs - 1) instanceof Argument.StarStar) {
      starstar = (Argument.StarStar) arguments.get(numNonStarArgs - 1);
      numNonStarArgs--;
    }
    Argument.Star star = null;
    if (numNonStarArgs > 0 && arguments.get(numNonStarArgs - 1) instanceof Argument.Star) {
      star = (Argument.Star) arguments.get(numNonStarArgs - 1);
      numNonStarArgs--;
    }
    // Inv: numNonStarArgs = |positional| + |named|

    StarlarkCallable callable = Starlark.getStarlarkCallable(fr.thread, fn);
    int numPositionalArguments = call.getNumPositionalArguments();

    if (numNonStarArgs == numPositionalArguments // no named args
        && star == null
        && starstar == null) {
      return evalPositionalOnlyCall(fr, callable, call, arguments, numPositionalArguments);
    }

    StarlarkCallable.ArgumentProcessor argumentProcessor =
        Starlark.requestArgumentProcessor(fr.thread, callable);

    // Set the location of the call before the first calls to argumentProcessor.add*Arg().
    Location loc = call.getLparenLocation();
    fr.setLocation(loc);

    // f(expr) -- positional args
    int i;
    for (i = 0; i < numPositionalArguments; i++) {
      Argument arg = arguments.get(i);
      argumentProcessor.addPositionalArg(eval(fr, arg.getValue()));
    }

    // f(id=expr) -- named args
    for (; i < numNonStarArgs; i++) {
      Argument arg = arguments.get(i);