build.js

const fs = require("fs");
const { flags } = require("@oclif/command");
const Command = require("@netlify/cli-utils");
const { zipFunctions } = require("@netlify/zip-it-and-ship-it");
const {
  NETLIFYDEV,
  NETLIFYDEVLOG,
  NETLIFYDEVWARN,
  NETLIFYDEVERR
} = require("netlify-cli-logo");

class FunctionsBuildCommand extends Command {
  async run() {
    const { flags, args } = this.parse(FunctionsBuildCommand);
    const { config } = this.netlify;

    const src = flags.src || config.build.functionsSource;
    const dst = flags.functions || config.build.functions;

    if (src === dst) {
      this.log(
        `${NETLIFYDEVERR} Source and destination for function build can't be the same`
      );
      process.exit(1);
    }

    if (!src || !dst) {
      if (!src)
        this.log(
          `${NETLIFYDEVERR} Error: You must specify a source folder with a --src flag or a functionsSource field in your config`
        );
      if (!dst)
        this.log(
          `${NETLIFYDEVERR} Error: You must specify a destination functions folder with a --functions flag or a functions field in your config`
        );
      process.exit(1);
    }

    fs.mkdirSync(dst, { recursive: true });

    this.log(`${NETLIFYDEVLOG} Building functions`);
    zipFunctions(src, dst, { skipGo: true });
    this.log(`${NETLIFYDEVLOG} Functions built to `, dst);
  }
}

FunctionsBuildCommand.description = `build functions locally
`;
FunctionsBuildCommand.aliases = ["function:build"];
FunctionsBuildCommand.flags = {
  functions: flags.string({
    char: "f",
    description: "Specify a functions folder to build to"
  }),
  src: flags.string({
    char: "s",
    description: "Specify the source folder for the functions"
  })
};

module.exports = FunctionsBuildCommand;