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Vex

#ARGS: two or more failed arguments

#ARGS means that two or more arguments of an op failed. The error keeps each failed argument as a cause. Thus one evaluation shows each problem, not only the first one.

Two arguments that both failorigin
app("add", ref("mass"), ref("speed"))
step 3 of 3

Result at A: #ARGS 2 arguments failed

originABCD
result#ARGS args#ARGS args#ARGS args#ARGS args

The program adds the fields mass and speed. The boxes have neither field, so both references give #N/A. The op add gives #ARGS, and its causes hold the two #N/A errors.

Kinds

Section titled “Kinds”
Kind Cause
args Two or more arguments of an op failed. Also two or more fields of a rec that failed.

Applicative evaluation

Section titled “Applicative evaluation”

The interpreter evaluates all arguments of an op before it decides. One failed argument gives its own error, with its own code. Two or more failed arguments give #ARGS. This code is not a spreadsheet code: it is the Vex way to keep more than one cause.

The trace shows the same thing. In the example above, the events of mass and speed both have an error, and the event of add has the code #ARGS.

The special forms if, and, or and ifError are different. They evaluate only the arguments that they need, so they do not give #ARGS.

The fix

Section titled “The fix”
  • Correct each argument. error.causes lists the errors in the order of the arguments.
  • Read each cause with formatError:
const r = chain.result("A");
if (!r.ok && r.error.code === "#ARGS") {
  for (const cause of r.error.causes ?? []) console.log(formatError(cause));
}

Refer to error values for the other codes.