Addresses: #1966 and #1802

Debugging

I know that the coerce middleware is being applied twice.
I ran the below example. I logged the execution of the functions that use applyMiddleware, and I logged the type/value of the arg during coercion.

const argv = yargs("rule add foo bar baz")
  .command("rule", "rule desc", (yargs) =>
    yargs.command("add <name> <abc...>", "add desc", (yargs) =>
      yargs.positional("abc", {
        type: "string",
        coerce: (arg) => console.log({ argType: typeof arg, arg }) || arg.join(" "),
      })
    )
  ).argv;

Logs look like this:

parse called
kRunYargsParserAndExecuteCommands called
runCommand called
parseAndUpdateUsage called
kRunYargsParserAndExecuteCommands called
runCommand called
parseAndUpdateUsage called
kRunYargsParserAndExecuteCommands called
pre-validation applyMiddleware called
{ argType: 'object', arg: [ 'bar', 'baz' ] }
post-validation applyMiddleware called
pre-validation applyMiddleware called
{ argType: 'string', arg: 'bar baz' }

The coerce middleware is only supposed to run before validation, but the pre-validation applyMiddleware gets called twice.

Fix

stack trace

get > parse > kRunYargsParserAndExecuteCommands > runCommand > applyMiddlewareAndGetResult > applyMiddleware

The problem

runCommand gets called recursively, which means that the middleware gets applied for each nested command.

Coerce middleware mutates argv, and repeating that mutation is undesired and can easily break.
ie: coerce: (arg) => arg.join()

The solution

I added two properties to the Middleware interface:

• mutates (bool): if the middleware mutates argv and should only be applied once.
• applied (bool): if the mutating middleware has already been applied once.

mutates defaults to false, but is set to true in addCoerceMiddleware.

I then check each middleware during applyMiddleware:

• If it mutates argv:
  • If it hasn't been applied, apply it and set applied to true.
  • If it mutates and has been applied, skip it.
• If it doesn't mutate argv:
  • handle the middleware like it normally would

Feedback

If you have recommendations for a better pattern, or better names for the interface properties I added, let me know. I feel like they could definitely be named better.