NPM should take most recent version

[xizhao]

NPM should by default take the most up-to-date one if it has a range of options from what is supplied.

Also added some if statements to prevent it from crashing in the case where it can't find a matching version.

[samertm]

Thanks for the PR!

Three comments: first, I think the 'master' branch is broken to begin with regarding the call to npm.commands.view, because when I run this in its own block:

var npm = require("npm");
npm.load(function(err, npm) {
    if (err) {
        console.error("npm.load failed: ", err);
        process.exit(1)
    }

    npm.commands.view(["--silent", "chalk@latest"], function(err,data) {
        if (err) {
            console.log("error occurred while resolving: " + JSON.stringify(err));
        } else if (!data || Object.keys(data).length == 0) {
            console.log("no npm package found with spec " + JSON.stringify(spec));
        } else {
            console.log('here');
            var chooseVersion = Object.keys(data)[0];
            var info = data[chooseVersion];
        }
    });
});

I get the following output:

npm http GET https://registry.npmjs.org/--silent
npm http 404 https://registry.npmjs.org/--silent
error occurred while resolving: {}

According to the docs, the correct way to silence the call is to pass 'true' as the second argument (https://www.npmjs.org/doc/api/npm-view.html). If you want to fix that in this PR too that would be awesome 😄

Second, I don't think Object.keys' order is defined: we shouldn't rely on the last item to be the latest. I don't know if there are any libraries in the javascript world for sorting strings based on the 'largest' version number, or if npm has a function to do that. What do you think?

Third, var info = Object.keys(data).slice(-1)[0]; will set info to a string representing the last key in its enumerable properties, when it's supposed to be the object that's represented by that version. Maybe

var latestVersion = OurAwesomeVersionNumberSortingFunction(Objects.keys(data))[0];
var info = data[latestVersion];

makes more sense.

[xizhao]

According to the docs, the correct way to silence the call is to pass 'true' as the second argument (https://www.npmjs.org/doc/api/npm-view.html). If you want to fix that in this PR too that would be awesome 😄

Yup, it is. Both should work depending on your NPM version, though. When I did this, I used:

npm.commands.view(["chalk@latest"], true, function(){});

Second, I don't think Object.keys' order is defined: we shouldn't rely on the last item to be the latest. I don't know if there are any libraries in the javascript world for sorting strings based on the 'largest' version number, or if npm has a function to do that. What do you think?

Technically, it shouldn't be defined, as dictionaries are orderless. However, I think this method is actually pretty reliable since NPM always responds with the version keys in order. The sorting function won't be a simple numerical parse + comparison, though, as version numbers can be anything in the NPM spec including something like 1.0.1-alpha. Luckily, NPM released semver which has rcompare, a compare function that parses and compares NPM version strings for descending sorts. This is used by NPM itself, so we'd only have to do:

var versions = Object.keys(data);
versions.sort(require('semver').rcompare);
var info = versions[0];

[samertm]

Technically, it shouldn't be defined, as dictionaries are orderless. However, I think this method is actually pretty reliable since NPM always responds with the version keys in order.

Huh, interesting. I think sorting the list is still a good idea, and I think your solution makes sense.