handling-output.md

@libreworks/cli

Examples

Handling Output

import type { ChalkInstance } from "chalk";
import type { Logger } from "ts-log";
import { Output, Program } from "@libreworks/cli";

const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));

async function makeLogEntries(logger: Logger, colors: ChalkInstance) {
  logger.info("Time to make the entries!");
  for (let i = 0; i < 10; i++) {
    logger.trace(`Testing ${colors.green(i)}`);
    await sleep(500);
  }
}

const output = Output.create({});

const program = new Program("@libreworks/cli:example-handling-output")
  .description("A test of @libreworks/cli")
  .version("0.0.0");

program.action(async function (options, cmd) {
  // Send data as-is to stdout.
  output.write("You called the handler!");

  // Use the logger, which writes to stderr.
  output.log.info("Handler invoked", { options });
  output.log.info(`Testing ${output.colors.red("123")}`);

  await Promise.all([
    // Send logs to stderr at regular intervals.
    makeLogEntries(output.logger, output.colors),

    // Show a loading indicator for 5 seconds.
    output.spinDuring(sleep(5000), "Reticulating Splines"),
  ]);

  output.log.warn("This is a warning!");

  try {
    throw new Error("A Big Problem");
  } catch (e) {
    // Stop the spinner and display the error.
    output.fail(e);
  }
});

await program.parseAsync();