task: You can't set both --download and --clear-cache flags

Error message

task: You can't set both --download and --clear-cache flags

What it means

Validate() rejects using --download together with --clear-cache. --clear-cache removes the downloaded Task cache while --download populates it, so running both in one invocation is contradictory. The error is returned before any task runs.

Source

Thrown at internal/flags/flags.go:209

	} else {
		// Explicit config: sync with fatih/color
		color.NoColor = !Color
	}
}

// isCI returns true if running in a CI environment
func isCI() bool {
	ci, _ := strconv.ParseBool(os.Getenv("CI"))
	return ci
}

func Validate() error {
	if Download && Offline {
		return errors.New("task: You can't set both --download and --offline flags")
	}

	if Download && ClearCache {
		return errors.New("task: You can't set both --download and --clear-cache flags")
	}

	if Global && Dir != "" {
		return errors.New("task: You can't set both --global and --dir")
	}

	if Output.Name != "group" {
		if Output.Group.Begin != "" {
			return errors.New("task: You can't set --output-group-begin without --output=group")
		}
		if Output.Group.End != "" {
			return errors.New("task: You can't set --output-group-end without --output=group")
		}
		if Output.Group.ErrorOnly {
			return errors.New("task: You can't set --output-group-error-only without --output=group")
		}
	}

View on GitHub (pinned to 385e5ad92a)

Solutions

Remove one of the two flags from the invocation
If you want a fresh binary: run --clear-cache first, then --download in a separate command
Inspect wrapper scripts/aliases that inject --clear-cache

Example fix

# before
task --download --clear-cache

# after
task --clear-cache && task --download

Defensive patterns

Strategy: validation

Validate before calling

if flags.Download && flags.ClearCache {
	return errors.New("cannot combine --download with --clear-cache")
}

Try / catch

if err := flags.Validate(); err != nil {
	if strings.Contains(err.Error(), "--download and --clear-cache") {
		fmt.Fprintln(os.Stderr, "run --clear-cache and --download as separate invocations")
		os.Exit(2)
	}
	return err
}

Prevention

Sequence cache reset and re-download as two separate commands
Avoid baking --clear-cache into every invocation 'for freshness'
Check chained shell commands for merged flags

When it happens

Trigger: Running `task --download --clear-cache ...` so both boolean flags are true when Validate() executes.

Common situations: Chained commands like `task --clear-cache && task --download` accidentally merged into one invocation; scripts that always pass --clear-cache for freshness.

Understand the failure class

Background: "mutually exclusive" flag errors: what "can't supply both nx and xx", "--raw is not compatible with -i" and "cannot be used with" mean, and how to fix them — this error's family across 29 libraries.

Related errors

AI-assisted analysis of go-task/task@385e5ad92a (2026-09-05). Data as JSON: /api/errors/bacc007e886fce59. Report an issue: GitHub.