Bug: inconsistencies with variadic function arguments

[diegommm]

Issue 1: nil as last variadic arg panics

This only happens when the number of arguments is greater than one. If nil is passed as the single variadic arg then the Issue 2 is observed.

Go Playground

The following code:

fmt.Println(expr.Eval(
	`sprintf("result: %v %v", 1, nil)`,
	map[string]any{
		"sprintf": fmt.Sprintf,
	},
))

Produces the output:

<nil> runtime error: index out of range [2] with length 2 (1:1)
 | sprintf("result: %v %v", 1, nil)
 | ^

Expected output:

result: 1 nil <nil>

Issue 2: single nil variadic arg interpreted as empty []any

Go Playground

The following code:

fmt.Println(expr.Eval(
	`thing(nil)`,
	map[string]any{
		"thing": func(arg ...any) string {
			return fmt.Sprintf("result: (%T) %v", arg[0], arg[0])
		},
	},
))

Produces the output:

result: ([]interface {}) [] <nil>

Expected output:

result: (<nil>) <nil> <nil>

[thokuest]

We are also affected by inconsistent handling of variadic arguments. The following code:

env := map[string]any{
	"countArgs": func(a ...any) int {
		return len(a)
	},
}

Is executed properly when invoked with countArgs(nil, 1) (output: 2), but errors with countArgs(1, nil), countArgs(nil, nil) and countArgs(nil, 1, nil).

code: countArgs(1, nil) => runtime error: index out of range [1] with length 1 (1:1)
 | countArgs(1, nil)
 | ^
code: countArgs(nil, 1) => 2
code: countArgs(nil, 1, nil) => runtime error: index out of range [2] with length 1 (1:1)
 | countArgs(nil, 1, nil)
 | ^
code: countArgs(nil, nil) => runtime error: index out of range [1] with length 1 (1:1)
 | countArgs(nil, nil)
 | ^

Go Playground

[antonmedv]

I will take a look at this bug.