escape codes and emojis when redirecting stderr to file

[kzc]

Would it be possible to automatically disable chalk escape codes and emojis if stderr is a is not a tty? (correction)

rollup version 0.39.0

$ echo "" > empty.js

$ node bin/rollup empty.js 2> err.txt

$ od -c err.txt
0000000  342 232 240   ️  **  **             033   [   1   m   G   e   n
0000020    e   r   a   t   e   d       a   n       e   m   p   t   y    
0000040    b   u   n   d   l   e 033   [   2   2   m  \n  \n            
0000055

[Rich-Harris]

Ha, whoops – didn't anticipate that scenario. Is this just a case of doing something like this?

const stderr = process.stderr.isTTY ?
  console.error.bind( console ) :
  str => console.error( stripControlCodesSomehow( str ) );

If so, any idea what stripControlCodesSomehow looks like?

[kzc]

If so, any idea what stripControlCodesSomehow looks like?

I think it's better to not emit these codes rather than strip them after the fact.

Only a single emoji was introduced as far as I can tell:

rollup/bin/src/runRollup.js

Line 157 in 11a2830

stderr( `⚠️ ${chalk.bold( warning.message )}` );

rather than strip it, that need not be emitted if stderr is is not a TTY. (correction)

I never used chalk before but I assume they must have a mode to not emit colors and control characters. If not, a wrapper could be made for chalk (red, grey, cyan, bold, dim, etc) to just be string passthroughs.

[kzc]

Although I think a passthrough chalk wrapper is the correct way to go, this regexp purports to remove terminal escape codes:

http://stackoverflow.com/questions/25245716/remove-all-ansi-colors-styles-from-strings/29497680#29497680

[kzc]

chalk.enabled = false;

https://github.com/chalk/chalk/blob/05f87e25e108726ee469aa56cc88fcc160a911ed/test.js#L135-L149

[kzc]

This patch fixes the redirected stderr issue. However, it uses require(). For the life of me I can't figure out how to get import to work with the mutable chalk singleton - Illegal reassignment to import 'chalk'?

diff --git a/bin/src/handleError.js b/bin/src/handleError.js
index aff6cea..0d5dd10 100644
--- a/bin/src/handleError.js
+++ b/bin/src/handleError.js
@@ -1,4 +1,6 @@
-import * as chalk from 'chalk';
+const chalk = require( "chalk" );
+
+if ( !process.stderr.isTTY ) chalk.enabled = false;
 
 function stderr ( msg ) {
        console.error( msg ); // eslint-disable-line no-console
diff --git a/bin/src/runRollup.js b/bin/src/runRollup.js
index f511de1..549157c 100644
--- a/bin/src/runRollup.js
+++ b/bin/src/runRollup.js
@@ -1,7 +1,7 @@
 import { realpathSync } from 'fs';
 import * as rollup from 'rollup';
 import relative from 'require-relative';
-import * as chalk from 'chalk';
+const chalk = require( "chalk" );
 import handleError from './handleError';
 import relativeId from '../../src/utils/relativeId.js';
 import SOURCEMAPPING_URL from './sourceMappingUrl.js';
@@ -154,7 +154,8 @@ function execute ( options, command ) {
                        if ( seen.has( str ) ) return;
                        seen.add( str );
 
-                       stderr( `⚠️   ${chalk.bold( warning.message )}` );
+                       const warnSymbol = process.stderr.isTTY ? `⚠️   ` : `Warning: `;
+                       stderr( `${warnSymbol}${chalk.bold( warning.message )}` );
 
                        if ( warning.url ) {
                                stderr( chalk.cyan( warning.url ) );

Amusing side note: I thought there was an escape code issue with emitting the dash in the warning (bytes 0xe2 0x80 0x93) until I learned that some rollup warnings use the Unicode Character 'EN DASH' (U+2013) instead of the typical 'HYPHEN-MINUS' (U+002D). Was not expecting that.

[Rich-Harris]

Thanks, have turned into a PR (#1206). The chalk thing can be fixed by doing...

import chalk from 'chalk';

...instead of...

import * as chalk from 'chalk';

...the end result is the same, except that Rollup doesn't think you're reassigning stuff illegally.

Amusing side note: I thought there was an escape code issue with emitting the dash in the warning (bytes 0xe2 0x80 0x93) until I learned that rollup warnings use the Unicode Character 'EN DASH' (U+2013) instead of the typical 'HYPHEN-MINUS' (U+002D). Was not expecting that.

Ha, that's what happens when you work in publishing I suppose — you obsess over the correct punctuation. Though I thought I'd been typing an EM DASH all these years, not an EN DASH (which isn't the correct mark). Oops! Will have to retrain my fingers.

[kzc]

Thanks.

So import chalk from 'chalk'; is mutable - I learn something new every day!

[braytak]

@kzc chalk.supportsColor.level will be 0 when you redirect to a file (or any destination that chalk deems as not color-capable).

Try this:

const chalk=require('chalk');
const util=require('util');
const o = {b: true, a:[1,2,3], s: 'string'}
console.log(util.inspect(o, {color: chalk.supportsColor.level !== 0}))

[kzc]

chalk.supportsColor.level will be 0 when you redirect to a file (or any destination that chalk deems as not color-capable).

@braytak It's been a while since I looked at this but the problem was not only a color issue. I didn't want emojis in the output (interfering with analysis) if it was not a TTY, hence the need for an explicit check.

I don't know the state of Rollup output now. It's probably changed and they may have reintroduced emojis unconditionally.

[shellscape]

@kzc I'm interested to learn more about your environment, given that utf-8 support is pretty widespread. Could you share some more with us?

[kzc]

@shellscape I am an old school programmer and loathe emojis. They interfere with analysis. There ought to be a way to disable them. You were looking for input in #2393, so I brought this up.

[kzc]

Just to follow up, an option to disable emojis is not uncommon in other projects:

yarnpkg/yarn#3660 (comment)

[shellscape]

Ah, I see. In that case, you should be able to use bash to accomplish that and still pipe to your desired destination:

sed 's/[^[:alnum:][:punct:][:space:]]//g' input

You might also be able wrap https://www.npmjs.com/package/emoji-strip in a CLI. I'm not sure that asking a library or app to filter certain unicode characters is reasonable solely based on personal preference, especially when a number of workarounds exist. And I'd question yarn's decision to add that option if I had any skin in the game.

Emoji were added in the Unicode Standard in version 6.0 that was released in 2010. I'd bet you're going to be progressively fighting an uphill battle as their use becomes more widespread. I'm just one maintainer though, and others may have different opinions.