From Discord: Bug in Effect CLI: --log-level=debug Argument Parsing Swallows Next Argument

[effect-bot]

Summary

A user reported a bug in the @effect/cli tool where using the '--log-level=debug' argument (with an '=' sign) causes the parser to incorrectly consume the next argument as well. The SetLogLevel handler removes '--log-level' flags before re-parsing, but due to a faulty check that matches '--log-level=debug', it removes the next argument unintentionally. For example, running 'bun effect-cli-log-level-bug.ts --log-level=debug --name=hello' results in '--name=hello' being ignored. The workaround is to use space-separated arguments like '--log-level debug --name=hello'. This issue highlights the need to properly parse and strip arguments when they contain '=' syntax to avoid swallowing subsequent flags.

Discord thread

https://discord.com/channels/795981131316985866/1478450569369620510

[jeffijoe]

Relevant snippet:

/**
 * @effect/cli bug: --log-level=<value> (with =) swallows the next argument.
 *
 * The SetLogLevel handler strips --log-level from args before re-parsing.
 * When using = syntax, it also incorrectly strips the NEXT arg because
 * `isLogLevelArg(args[i - 1])` matches "--log-level=debug".
 *
 * Bug case:
 *   bun effect-cli-log-level-bug.ts --log-level=debug --name=hello
 *   # name = None  ← --name=hello was swallowed
 *
 * Workaround (space-separated --log-level):
 *   bun effect-cli-log-level-bug.ts --log-level debug --name=hello
 *   # name = Some("hello")  ← correct
 */
import { Command, Options } from "@effect/cli"
import { BunContext, BunRuntime } from "@effect/platform-bun"
import { Console, Effect } from "effect"

const cmd = Command.make(
  "repro",
  {
    name: Options.text("name").pipe(Options.optional),
  },
  ({ name }) => Console.log("name =", name),
)

Command.run(cmd, { name: "repro", version: "0.0.0" })(process.argv).pipe(
  Effect.provide(BunContext.layer),
  BunRuntime.runMain,
)