serverless-webpack automatic config and externals prototype https://github.com/serverless-heaven/serverless-webpack/issues/399

serverless-webpack-auto.js

// prototype for https://github.com/serverless-heaven/serverless-webpack/issues/399

'use strict';

const fs = require('fs');

const webpackConfigFile = "webpack.config.js";

class OpenWhiskExtServerlessPlugin {

    constructor(serverless, options) {
        this.serverless = serverless;
        this.options = options;

        this.hooks = {
            'before:package:initialize': this.beforePackage.bind(this),
            'after:package:finalize': this.afterPackage.bind(this),
        };
    }
  
    beforePackage() {
        if (this.isWebpackPluginInstalled()) {
            if (fs.existsSync(webpackConfigFile)) {
                this.log("Custom " + webpackConfigFile + " detected");
            } else {
                this.log("Automatic webpack configuration for openwhisk");
                return this.writeWebpackConfig();
            }
        } else {
            this.log("Plugin serverless-webpack is not installed, skipping serverless-openwhisk webpack feature");
        }
        return Promise.resolve();
    }

    afterPackage() {
        if (this.doCleanup) {
            var that = this;
            return fs.unlink(webpackConfigFile, function(err) {
                if (err) {
                    return console.error(err);
                }

                that.debugLog("Removed " + webpackConfigFile);
            });
        }
    }

    isWebpackPluginInstalled() {
        // check for presence of "webpack" command in at least one plugin
        return this.serverless.pluginManager.getPlugins().some( function(plugin) {
            return null !== (((plugin || {}).commands || {}).webpack || null);
        });
    }
    
    writeWebpackConfig() {
        const that = this;
        const mode = this.options.mode || "production";
        
        var externals = '{}';
        
        // TODO: check for different runtimes in `this.serverless.service.functions.*.runtime`
        //       and give out a warning then
        console.log("Provider runtime", this.serverless.service.provider.runtime);
        console.log("API function runtime", this.serverless.service.functions.api.runtime);
        
        var runtime = this.serverless.service.provider.runtime;
        if (runtime) {
            try {
                externals = JSON.stringify(require('./externals/' + runtime.replace(":", "_") + '.json'));
            } catch (e) {
                this.log("no externals found for runtime: " + runtime)
            }
        } else {
            this.log("no provider.runtime configured, cannot exclude any preinstalled node dependencies");
        }
        
        const webpackConfig =
`
// auto-created by serverless-openwhisk plugin on demand
// this file should be automatically deleted after the build
// and not be checked in unless you want to have a custom
// webpack configuration
module.exports = {
    mode: '${mode}',
    target: 'node',
    externals: ${externals}
}
`;

        return fs.writeFile(webpackConfigFile, webpackConfig,
            function(err) {
                if (err) {
                    return console.error(err);
                }

                that.debugLog("Created " + webpackConfigFile);
                that.doCleanup = true;
            }
        );
    }
    
    debugLog(msg) {
        if (process.env.SLS_DEBUG) {
            this.log(msg);
        }
    }
    
    log(msg) {
        this.serverless.cli.log("[serverless-openwhisk-extension] " + msg);
    }
  
}

module.exports = OpenWhiskExtServerlessPlugin; 

z_externals__nodejs_6.json

// an example externals config for the openwhisk nodejs:6 container
// included in js above via require('./externals/' + runtime)
// standard ones would be distributed with the plugin
// but there would need to be a way to reference custom ones, not sure how that's best done yet
{
  "cookie": "cookie",
  "accepts": "accepts",
  "http-errors": "http-errors",
  "debug": "debug",
  "content-disposition": "content-disposition",
  "jsonpointer": "jsonpointer",
  "forever-agent": "forever-agent",
  "escape-html": "escape-html",
  ...
}