cockpit.spawn() - how to wait for finish?

[.]

Hello,
First of all: thank you very much for maintaining this great project!

I'm C programmer learning now Cockpit. My problem is as follows: for some
of the operation I must use external helper and I must wait for it output.
The cockpit.spawn() function returns the promise, which is non-blocking
operation (as expected). How can I make it work as blocking one? Which
mean: the rest of the code in the function should be done after receiving
full output of the cockpit.spawn (done() or fail())

best regards,
Magik

[Daniel.]

You are looking for `await`, if you use starter kit you have it already
configured. With it you can "wait" for a promisse to complete,

Take a look here:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements...

Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> Hello,
> First of all: thank you very much for maintaining this great project!
>
> I'm C programmer learning now Cockpit. My problem is as follows: for some
> of the operation I must use external helper and I must wait for it output.
> The cockpit.spawn() function returns the promise, which is non-blocking
> operation (as expected). How can I make it work as blocking one? Which
> mean: the rest of the code in the function should be done after receiving
> full output of the cockpit.spawn (done() or fail())
>
> best regards,
> Magik
>
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[.]

Daniel,

Thank you very much for the answer! I was not using starter-pack, I've just
started with creating direct on the server the manifest, html, css and js
files. I'm not using npm at all. Is is required for Cockpit functionality?
Of course I'll give starter-pack a try at once.

Magik

śr., 9 sty 2019 o 21:55 Daniel.  napisał(a):
> You are looking for `await`, if you use starter kit you have it already
> configured. With it you can "wait" for a promisse to complete,
>
> Take a look here:
> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements...
>
> Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> > Hello,
> > First of all: thank you very much for maintaining this great project!
> >
> > I'm C programmer learning now Cockpit. My problem is as follows: for some
> > of the operation I must use external helper and I must wait for it output.
> > The cockpit.spawn() function returns the promise, which is non-blocking
> > operation (as expected). How can I make it work as blocking one? Which
> > mean: the rest of the code in the function should be done after receiving
> > full output of the cockpit.spawn (done() or fail())
> >
> > best regards,
> > Magik
> >
> > cockpit-devel mailing list -- [e-mail]
> > To unsubscribe send an email to
> > [e-mail]
> > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedorahosted.org/archives/list/[e-mail]...
>
> --
> “If you're going to try, go all the way. Otherwise, don't even start. ..."
>   Charles Bukowski
> _______________________________________________
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[Daniel.]

It's not required but is a big shortcut..  The newer browsers support
async, you can try it without Babel, it's up to you

Em qua, 9 de jan de 2019 7:04 PM, . <[e-mail] escreveu:
> Daniel,
>
> Thank you very much for the answer! I was not using starter-pack, I've
> just started with creating direct on the server the manifest, html, css and
> js files. I'm not using npm at all. Is is required for Cockpit
> functionality?
> Of course I'll give starter-pack a try at once.
>
> Magik
>
> śr., 9 sty 2019 o 21:55 Daniel.  napisał(a):
> > You are looking for `await`, if you use starter kit you have it already
> > configured. With it you can "wait" for a promisse to complete,
> >
> > Take a look here:
> > https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements...
> >
> > Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> > > Hello,
> > > First of all: thank you very much for maintaining this great project!
> > >
> > > I'm C programmer learning now Cockpit. My problem is as follows: for
> > > some of the operation I must use external helper and I must wait for it
> > > output. The cockpit.spawn() function returns the promise, which is
> > > non-blocking operation (as expected). How can I make it work as blocking
> > > one? Which mean: the rest of the code in the function should be done after
> > > receiving full output of the cockpit.spawn (done() or fail())
> > >
> > > best regards,
> > > Magik
> > >
> > > cockpit-devel mailing list -- [e-mail]
> > > To unsubscribe send an email to
> > > [e-mail]
> > > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > > List Archives:
> > > https://lists.fedorahosted.org/archives/list/[e-mail]...
> >
> > --
> > “If you're going to try, go all the way. Otherwise, don't even start.
> > ..."
> >   Charles Bukowski
> > _______________________________________________
> > cockpit-devel mailing list -- [e-mail]
> > To unsubscribe send an email to
> > [e-mail]
> > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedorahosted.org/archives/list/[e-mail]...
>
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[.]

Daniel,

Thank you for your answer. Could you please provide me with the really
short (few lines) example of practical use of cockpit.spawn() in
blocking-like mode?

śr., 9 sty 2019 o 22:57 Daniel.  napisał(a):
> It's not required but is a big shortcut..  The newer browsers support
> async, you can try it without Babel, it's up to you
>
> Em qua, 9 de jan de 2019 7:04 PM, . <[e-mail] escreveu:
> > Daniel,
> >
> > Thank you very much for the answer! I was not using starter-pack, I've
> > just started with creating direct on the server the manifest, html, css and
> > js files. I'm not using npm at all. Is is required for Cockpit
> > functionality?
> > Of course I'll give starter-pack a try at once.
> >
> > Magik
> >
> > śr., 9 sty 2019 o 21:55 Daniel.  napisał(a):
> > > You are looking for `await`, if you use starter kit you have it already
> > > configured. With it you can "wait" for a promisse to complete,
> > >
> > > Take a look here:
> > > https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements...
> > >
> > > Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> > > > Hello,
> > > > First of all: thank you very much for maintaining this great project!
> > > >
> > > > I'm C programmer learning now Cockpit. My problem is as follows: for
> > > > some of the operation I must use external helper and I must wait for it
> > > > output. The cockpit.spawn() function returns the promise, which is
> > > > non-blocking operation (as expected). How can I make it work as blocking
> > > > one? Which mean: the rest of the code in the function should be done after
> > > > receiving full output of the cockpit.spawn (done() or fail())
> > > >
> > > > best regards,
> > > > Magik
> > > >
> > > > cockpit-devel mailing list -- [e-mail]
> > > > To unsubscribe send an email to
> > > > [e-mail]
> > > > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > > > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > > > List Archives:
> > > > https://lists.fedorahosted.org/archives/list/[e-mail]...
> > >
> > > --
> > > “If you're going to try, go all the way. Otherwise, don't even start.
> > > ..."
> > >   Charles Bukowski
> > > _______________________________________________
> > > cockpit-devel mailing list -- [e-mail]
> > > To unsubscribe send an email to
> > > [e-mail]
> > > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > > List Archives:
> > > https://lists.fedorahosted.org/archives/list/[e-mail]...
> >
> > cockpit-devel mailing list -- [e-mail]
> > To unsubscribe send an email to
> > [e-mail]
> > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedorahosted.org/archives/list/[e-mail]...
>
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[Daniel.]

Note that for using it you need to enable it support on babel, welcome to
modern javascript, these are the pieces of software that I recommend you to
get familiar with it: Webpack and Babel.

Webpack will bundle all your javascript (css and other stuff) in a single
bundle. Babel will let you to develop on newer versions of javascript that
would not be available on old browsers, and it will transpile to old
javascript

Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> Hello,
> First of all: thank you very much for maintaining this great project!
>
> I'm C programmer learning now Cockpit. My problem is as follows: for some
> of the operation I must use external helper and I must wait for it output.
> The cockpit.spawn() function returns the promise, which is non-blocking
> operation (as expected). How can I make it work as blocking one? Which
> mean: the rest of the code in the function should be done after receiving
> full output of the cockpit.spawn (done() or fail())
>
> best regards,
> Magik
>
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[.]

Daniel,

I see. Could you please provide me with the small code example for await?

Magik

śr., 9 sty 2019 o 22:00 Daniel.  napisał(a):
> Note that for using it you need to enable it support on babel, welcome to
> modern javascript, these are the pieces of software that I recommend you to
> get familiar with it: Webpack and Babel.
>
> Webpack will bundle all your javascript (css and other stuff) in a single
> bundle. Babel will let you to develop on newer versions of javascript that
> would not be available on old browsers, and it will transpile to old
> javascript
>
> Em qua, 9 de jan de 2019 às 18:52, .  escreveu:
> > Hello,
> > First of all: thank you very much for maintaining this great project!
> >
> > I'm C programmer learning now Cockpit. My problem is as follows: for some
> > of the operation I must use external helper and I must wait for it output.
> > The cockpit.spawn() function returns the promise, which is non-blocking
> > operation (as expected). How can I make it work as blocking one? Which
> > mean: the rest of the code in the function should be done after receiving
> > full output of the cockpit.spawn (done() or fail())
> >
> > best regards,
> > Magik
> >
> > cockpit-devel mailing list -- [e-mail]
> > To unsubscribe send an email to
> > [e-mail]
> > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedorahosted.org/archives/list/[e-mail]...
>
> --
> “If you're going to try, go all the way. Otherwise, don't even start. ..."
>   Charles Bukowski
> _______________________________________________
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[Martin Pitt]

Hello Magik,

. [2019-01-09 21:51 +0100]:
> I'm C programmer learning now Cockpit. My problem is as follows: for some
> of the operation I must use external helper and I must wait for it output.
> The cockpit.spawn() function returns the promise, which is non-blocking
> operation (as expected). How can I make it work as blocking one? Which
> mean: the rest of the code in the function should be done after receiving
> full output of the cockpit.spawn (done() or fail())

This is a common pitfal when coming from the world of synchronous programming
languages (such as C or Python) and starting with asynchronous JavaScript.
Daniel's await proposal can certainly help to make async code look like it was
written in a sync style; but honestly, it's really best to let go of this
pattern when writing JS.

So instead of

output = cockpit.spawn(..).make_this_magically_sync();
  followup_action(output);

actually use JavaScript promises as they are intended:

cockpit.spawn(..)
      .then(output => {
          followup_action(output);
      })
      .catch(err => {
          console.error(err);
      });

i. e. organize the stuff that depends on the result into promise handlers.

Martin

[.]

Martin,

Thank you very much for the answer! Unfortunately I'm still stuck :-(
Please take a look at the following code and tell me why it's still
asynchronous. It display properly messages: "testFunct" and then "end of
testFunct", but it never reach the .then or .done.
Thank you in advance!

function testFunc() {
     alert("testFunc");
     lic = cockpit.spawn([
"/usr/share/cockpit/testSoftware/connectExternalSystem"], {
     directory: "/usr/share/cockpit/testSoftware",
     err: "message"
     })
     .then(function() {
     alert("in .then of testFunc. Error: "+message);
            })
            .done(function() {
     alert("in .done of testFunc. Error: "+message);
     });
     alert("end of testFunc");
    }

czw., 10 sty 2019 o 09:02 Martin Pitt  napisał(a):
> Hello Magik,
>
> . [2019-01-09 21:51 +0100]:
> > I'm C programmer learning now Cockpit. My problem is as follows: for some
> > of the operation I must use external helper and I must wait for it
>
> output.
> > The cockpit.spawn() function returns the promise, which is non-blocking
> > operation (as expected). How can I make it work as blocking one? Which
> > mean: the rest of the code in the function should be done after receiving
> > full output of the cockpit.spawn (done() or fail())
>
> This is a common pitfal when coming from the world of synchronous
> programming
> languages (such as C or Python) and starting with asynchronous JavaScript.
> Daniel's await proposal can certainly help to make async code look like it
> was
> written in a sync style; but honestly, it's really best to let go of this
> pattern when writing JS.
>
> So instead of
>
> output = cockpit.spawn(..).make_this_magically_sync();
>   followup_action(output);
>
> actually use JavaScript promises as they are intended:
>
> cockpit.spawn(..)
>       .then(output => {
>           followup_action(output);
>       })
>       .catch(err => {
>           console.error(err);
>       });
>
> i. e. organize the stuff that depends on the result into promise handlers.
>
> Martin
> _______________________________________________
> cockpit-devel mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]
> Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> List Archives:
> https://lists.fedorahosted.org/archives/list/[e-mail]...

[.]

What interesting: if I define .then just as:
.then(alert("in .then"));
then it works fine. But if i use the function() inside or the notation
you've provided:
            .then(output => {
                alert(output);
            });

then system never reaches the .then. What I'm doing wrong?

pt., 11 sty 2019 o 20:44 .  napisał(a):
> Martin,
>
> Thank you very much for the answer! Unfortunately I'm still stuck :-(
> Please take a look at the following code and tell me why it's still
> asynchronous. It display properly messages: "testFunct" and then "end of
> testFunct", but it never reach the .then or .done.
> Thank you in advance!
> function testFunc() {
>  alert("testFunc");
>  lic = cockpit.spawn([
>
> "/usr/share/cockpit/testSoftware/connectExternalSystem"], {
>      directory: "/usr/share/cockpit/testSoftware",
>      err: "message"
>      })
>      .then(function() {
>      alert("in .then of testFunc. Error: "+message);
>             })
>             .done(function() {
>      alert("in .done of testFunc. Error: "+message);
>      });
>      alert("end of testFunc");
>     }
>
> czw., 10 sty 2019 o 09:02 Martin Pitt  napisał(a):
> > Hello Magik,
> >
> > . [2019-01-09 21:51 +0100]:
> > > I'm C programmer learning now Cockpit. My problem is as follows: for
> >
> > some
> > > of the operation I must use external helper and I must wait for it
> >
> > output.
> > > The cockpit.spawn() function returns the promise, which is non-blocking
> > > operation (as expected). How can I make it work as blocking one? Which
> > > mean: the rest of the code in the function should be done after
> >
> > receiving
> > > full output of the cockpit.spawn (done() or fail())
> >
> > This is a common pitfal when coming from the world of synchronous
> > programming
> > languages (such as C or Python) and starting with asynchronous JavaScript.
> > Daniel's await proposal can certainly help to make async code look like
> > it was
> > written in a sync style; but honestly, it's really best to let go of this
> > pattern when writing JS.
> >
> > So instead of
> >
> > output = cockpit.spawn(..).make_this_magically_sync();
> >   followup_action(output);
> >
> > actually use JavaScript promises as they are intended:
> >
> > cockpit.spawn(..)
> >       .then(output => {
> >           followup_action(output);
> >       })
> >       .catch(err => {
> >           console.error(err);
> >       });
> >
> > i. e. organize the stuff that depends on the result into promise handlers.
> >
> > Martin
> > _______________________________________________
> > cockpit-devel mailing list -- [e-mail]
> > To unsubscribe send an email to
> > [e-mail]
> > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedorahosted.org/archives/list/[e-mail]...

[.]

OK, problem solved.

pt., 11 sty 2019 o 21:18 .  napisał(a):
> What interesting: if I define .then just as:
> .then(alert("in .then"));
> then it works fine. But if i use the function() inside or the notation
> you've provided:
>             .then(output => {
>                 alert(output);
>             });
>
> then system never reaches the .then. What I'm doing wrong?
>
> pt., 11 sty 2019 o 20:44 .  napisał(a):
> > Martin,
> >
> > Thank you very much for the answer! Unfortunately I'm still stuck :-(
> > Please take a look at the following code and tell me why it's still
> > asynchronous. It display properly messages: "testFunct" and then "end of
> > testFunct", but it never reach the .then or .done.
> > Thank you in advance!
> > function testFunc() {
> >  alert("testFunc");
> >  lic = cockpit.spawn([
> >
> > "/usr/share/cockpit/testSoftware/connectExternalSystem"], {
> >      directory: "/usr/share/cockpit/testSoftware",
> >      err: "message"
> >      })
> >      .then(function() {
> >      alert("in .then of testFunc. Error: "+message);
> >             })
> >             .done(function() {
> >      alert("in .done of testFunc. Error: "+message);
> >      });
> >      alert("end of testFunc");
> >     }
> >
> > czw., 10 sty 2019 o 09:02 Martin Pitt  napisał(a):
> > > Hello Magik,
> > >
> > > . [2019-01-09 21:51 +0100]:
> > > > I'm C programmer learning now Cockpit. My problem is as follows: for
> > >
> > > some
> > > > of the operation I must use external helper and I must wait for it
> > >
> > > output.
> > > > The cockpit.spawn() function returns the promise, which is non-blocking
> > > > operation (as expected). How can I make it work as blocking one? Which
> > > > mean: the rest of the code in the function should be done after
> > >
> > > receiving
> > > > full output of the cockpit.spawn (done() or fail())
> > >
> > > This is a common pitfal when coming from the world of synchronous
> > > programming
> > > languages (such as C or Python) and starting with asynchronous
> > > JavaScript.
> > > Daniel's await proposal can certainly help to make async code look like
> > > it was
> > > written in a sync style; but honestly, it's really best to let go of this
> > > pattern when writing JS.
> > >
> > > So instead of
> > >
> > > output = cockpit.spawn(..).make_this_magically_sync();
> > >   followup_action(output);
> > >
> > > actually use JavaScript promises as they are intended:
> > >
> > > cockpit.spawn(..)
> > >       .then(output => {
> > >           followup_action(output);
> > >       })
> > >       .catch(err => {
> > >           console.error(err);
> > >       });
> > >
> > > i. e. organize the stuff that depends on the result into promise
> > > handlers.
> > >
> > > Martin
> > > _______________________________________________
> > > cockpit-devel mailing list -- [e-mail]
> > > To unsubscribe send an email to
> > > [e-mail]
> > > Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html
> > > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > > List Archives:
> > > https://lists.fedorahosted.org/archives/list/[e-mail]...

[Martin Pitt]

Hello Magic,

. [2019-01-11 20:44 +0100]:
> Thank you very much for the answer! Unfortunately I'm still stuck :-(
> Please take a look at the following code and tell me why it's still
> asynchronous. It display properly messages: "testFunct" and then "end of
> testFunct", but it never reach the .then or .done.

Seems you eventually figured it out on your own, but FTR:
> function testFunc() {
>  alert("testFunc");
>  lic = cockpit.spawn([
>
> "/usr/share/cockpit/testSoftware/connectExternalSystem"], {
>      directory: "/usr/share/cockpit/testSoftware",
>      err: "message"
>      })
>      .then(function() {
>      alert("in .then of testFunc. Error: "+message);
>             })

Note that this only gets called if connectExternalSystem succeeds -- *message*
is not defined here, so this can't work. What you want is

.then(output => alert("finished, output:", output))
  .catch(error => alert("failed, error:", error);
>         .done(function() {
>  alert("in .done of testFunc. Error: "+message);
>  });

And this makes no ssense at all -- alert doesn't return a promise, to calling
.done() on alert()'s result also doesn't work.

Martin

[.]

Martin,
It was easier to me to take a look at sources of JS compiler and find in
the implementation differences between "function()" and "function" - now
everything is clear for me :-)
Anyway - thank you for all explanations!

sob., 12 sty 2019 o 17:36 Martin Pitt  napisał(a):
> Hello Magic,
>
> . [2019-01-11 20:44 +0100]:
> > Thank you very much for the answer! Unfortunately I'm still stuck :-(
> > Please take a look at the following code and tell me why it's still
> > asynchronous. It display properly messages: "testFunct" and then "end of
> > testFunct", but it never reach the .then or .done.
>
> Seems you eventually figured it out on your own, but FTR:
> > function testFunc() {
> >  alert("testFunc");
> >  lic = cockpit.spawn([
> >
> > "/usr/share/cockpit/testSoftware/connectExternalSystem"], {
> >      directory: "/usr/share/cockpit/testSoftware",
> >      err: "message"
> >      })
> >      .then(function() {
> >      alert("in .then of testFunc. Error: "+message);
> >             })
>
> Note that this only gets called if connectExternalSystem succeeds --
> *message*
> is not defined here, so this can't work. What you want is
>
> .then(output => alert("finished, output:", output))
>   .catch(error => alert("failed, error:", error);
> >         .done(function() {
> >  alert("in .done of testFunc. Error: "+message);
> >  });
>
> And this makes no ssense at all -- alert doesn't return a promise, to
> calling
> .done() on alert()'s result also doesn't work.
>
> Martin
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