collectFile(): and collect(): a way to return an error message if collection is finally empty

[gael-millot]

Hi.

Thanks for your excellent work !
It would be important to have a new argument for collectFile(): and collect(), that returns an error message if collections by these functions are finally empty.
Or is there an alternative way to control this ?
Because for the moment, I do not know how to control this aspect when gathering outputs from parallele processes.
Thanks !

Gael.

[bentsherman]

You could use count and subscribe to check whether the incoming channel is empty before you call collect / collectFile. Here's an example:

// items to collect
ch_samples = Channel.empty()

ch_samples
  | count
  | subscribe { n ->
    if ( n == 0 ) error "There are no items to collect"
  }

ch_samples
  | collect

[gael-millot]

Hi Ben. Thanks a lot ! It works. Best, Gael. De : Ben Sherman ***@***.***> Envoyé : mercredi 8 mars 2023 16:04 À : nextflow-io/nextflow ***@***.***> Cc : Gael MILLOT ***@***.***>; Author ***@***.***> Objet : Re: [nextflow-io/nextflow] collectFile(): and collect(): a way to return an error message if collection is finally empty (Issue #3730) You could use count and subscribe to check whether the incoming channel is empty before you call collect / collectFile. Here's an example: // items to collect ch_samples = Channel.empty() ch_samples | count | subscribe { n -> if ( n == 0 ) error "There are no items to collect" } ch_samples | collect — Reply to this email directly, view it on GitHub<https://urldefense.com/v3/__https:/github.com/nextflow-io/nextflow/issues/3730*issuecomment-1460297651__;Iw!!JFdNOqOXpB6UZW0!qmf77muDi5aRv9-2IIrHYwER407BQkD4v9hieMDXZMaxWmvamijqICKt8oaQPrSlcuYkxD3Uuo9kT1osoAuHa-spQtKr$>, or unsubscribe<https://urldefense.com/v3/__https:/github.com/notifications/unsubscribe-auth/AOVRK6UZ2LE44ANMS7IN5C3W3CNVZANCNFSM6AAAAAAVTYVX6A__;!!JFdNOqOXpB6UZW0!qmf77muDi5aRv9-2IIrHYwER407BQkD4v9hieMDXZMaxWmvamijqICKt8oaQPrSlcuYkxD3Uuo9kT1osoAuHa3B37R0N$>. You are receiving this because you authored the thread.Message ID: ***@***.******@***.***>>