Future.wait() can't wait without a fiber (while waiting on another future in Meteor.method)

future, meteor

Solution

Wrap your callback into `Meteor.bindEnvironment`, example:

fs.readdir(dir, Meteor.bindEnvironment(function (err, res) {
    if (err) future.throw(err);
    future.return(res);
}, function (err) { console.log("couldn't wrap the callback"); });

`Meteor.bindEnvironment` does a lot of things and one of them is to make sure callback is running in a Fiber.

Another thing that could be helpful is `var funcSync = Meteor._wrapAsync(func)` which utilizes futures and allows use to call a function in synchronous style (but it is still async).

Watch these videos on evented mind if you want to know more: https://www.eventedmind.com/posts/meteor-dynamic-scoping-with-environment-variables https://www.eventedmind.com/posts/meteor-what-is-meteor-bindenvironment

Problem

In `Meteor`, I'm writing a method that will have to check a certain path's subdirectories for new files. I first would like to just list the subdirectories within `Meteor` after which I `child_process.exec` a simple bash script that lists files added since the last time it executed. I'm having some issues getting the directory discovery to be async (`Error: Can't wait without a fiber`). I've written a synchronous version but having both `fs.readdir` and `fs.stat` in stead of their synchronous alternatives allows me to catch errors. Here's the code: ``` function listDirs(dir, isDir){ var future1 = new Future();fs.readdir(dir, function(err, files){ if (err) throw new Meteor.error(500, "Error listing files", err); var dirs = _.map(files, function(file){ var future2 = new Future(); var resolve2 = future2.resolver(); fs.stat(dir+file, function(err, stats){ if (err) throw new Meteor.error(500, "Error statting files", err); if (stats.isDirectory() == isDir && file.charAt(0) !== '.') resolve2(err, file); }); return future2; }); Future.wait(dirs); //var result = _.invoke(dirs, 'get'); future1['return'](_.compact(dirs)); }); return future1.wait(); } ``` The error `Error: Can't wait without a fiber` has to do with `future2`. When I comment out `Future.wait(dirs)` the server doesn't crash anymore, but that's about as far as I got in trying to solve this. :/ Another `_.map` function I use in another part of the method works fine with futures. (see also https://gist.github.com/possibilities/3443021 where I found my inspiration)

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