Default logger middleware doesn't check that stdout is a TTY

[gpanders]

What version of Hono are you using?

4.6.16

What runtime/platform is your app running on? (with version if possible)

Cloudflare Workers

What steps can reproduce the bug?

Use the default logger middleware provided by Hono https://hono.dev/docs/middleware/builtin/logger

Observe that emitted logs contain ANSI escape sequences when the output is not a TTY:

This screenshot is taken from Cloudflare Workers logs, but the same would be true for any log output which is not a terminal.

What is the expected behavior?

Hono should check that stdout is a TTY when determining whether or not to emit ANSI escape sequences for colors:

hono/src/utils/color.ts

Lines 13 to 26 in 2ead4d8

	export function getColorEnabled(): boolean {
	// eslint-disable-next-line @typescript-eslint/no-explicit-any
	const { process, Deno } = globalThis as any
	const isNoColor =
	typeof Deno?.noColor === 'boolean'
	? (Deno.noColor as boolean)
	: process !== undefined
	? // eslint-disable-next-line no-unsafe-optional-chaining
	'NO_COLOR' in process?.env
	: false
	return !isNoColor
	}

In Node this can be done with Boolean(process.stdout.isTTY) === true https://nodejs.org/api/tty.html#tty

Deno has Deno.stdout.isTerminal() https://docs.deno.com/api/deno/~/Deno.stdout.isTerminal

What do you see instead?

No response

Additional information

A workaround in the meantime is to set NO_COLOR manually if stdout is not a TTY:

if (Boolean(process.stdout.isTTY) === false) {
    process.env["NO_COLOR"] = "1"
}

Note however that even this will not work in Cloudflare Workers because of another issue with the process polyfill: unjs/unenv#380

[yusukebe]

HI @gpanders

Thank you for raising the issue. There is a similar issue #3751. We have the hacky way, but using checking TTY is a good idea.

Hey @ryuapp! What do you think of checking TTY for the logger?