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.

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.

Appendix: 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")
		}
	}

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