Add a public API for installation and linking

[patrickheeney]

I am using pnpm as part of a mono repo and I need to install a subset of the package.json files. Something like pnpm install -f package.local.json. Since files are not supported, I looked at integration within my own CLI tool. These are the problems I ran into:

const install = require('pnpm/lib/cmd/install');
const installError = require('pnpm/lib/err');

return install(dependencies, { quiet: false }).catch(installError);

On the surface, this looks pretty good, but it unfortunately uses the package.json from the current directory of my CLI tool as root, so it installs them in the wrong location.

const install = require('pnpm/lib/install_multiple');
const installConfig = require('pnpm/lib/config');
const installLog = require('pnpm/lib/logger');
const installError = require('pnpm/lib/err');
const installPeers = require('pnpm/lib/install/link_peers');

const ctx = {
  root: rootPath,
  store: path.resolve(rootPath, installConfig.store_path),
  log: installLog()
};

return install(ctx, dependencies, path.join(ctx.root, 'node_modules'), { quiet: false })
  .then(_ => installPeers(null, ctx.store, ctx.installs))
  .catch(installError);

This did the trick, but as you can see its pretty verbose and reaches quite a bit into the pnpm internals. It would be nice to have a public API that could do something like this:

import pnpmApi from 'pnpm/api';

return pnpmApi.install(dependencies, rootPath, { quiet: false });

The implementation would look like my last snippet above. Let me know if you would accept a pull request for this?

EDIT: Also wanted to point out that installPeers accepts pkg as a first argument, but it does not use it in the function.

[rstacruz]

ah, neat! I don't think making a separate pnpm/api is the way to go here... i think it's best we make install() take the things you need—less code paths to maintain.

[davej]

@patrickheeney looks good, only thing I would add is that it would be nice if it exposed an EventEmitter to track progress rather than logging to console. Perhaps even better might be a generator but that could be more difficult to implement.

[davej]

@zkochan: Finally got around to using this API. Works nicely! Only thing that is missing (IMO) is to return the installed package's info. So, for example, I could find out which version was actually installed.

[zkochan]

Shouldn't be hard to do it. Here that info is being written to the store.json. So we can get it from storeJson.dependencies[installedPkgName]