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tty: add NO_COLOR and FORCE_COLOR support #26485

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tty: add NO_COLOR and FORCE_COLOR support #26485

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af0b138
tty: add NO_COLOR and FORCE_COLOR support
BridgeAR Mar 7, 2019
8708e7e
fixup! tty: add NO_COLOR and FORCE_COLOR support
BridgeAR Mar 8, 2019
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20 changes: 14 additions & 6 deletions doc/api/tty.md
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Expand Up @@ -144,8 +144,9 @@ position.
added: v9.9.0
-->

* `env` {Object} An object containing the environment variables to check.
**Default:** `process.env`.
* `env` {Object} An object containing the environment variables to check. This
enables simulating the usage of a specific terminal. **Default:**
`process.env`.
* Returns: {number}

Returns:
Expand All @@ -159,11 +160,18 @@ Use this to determine what colors the terminal supports. Due to the nature of
colors in terminals it is possible to either have false positives or false
negatives. It depends on process information and the environment variables that
may lie about what terminal is used.
To enforce a specific behavior without relying on `process.env` it is possible
to pass in an object with different settings.
It is possible to pass in an `env` object to simulate the usage of a specific
terminal. This can be useful to check how specific environment settings behave.

To enforce a specific color support, use one of the below environment settings.

* 2 colors: `FORCE_COLOR = 0` (Disables colors)
* 16 colors: `FORCE_COLOR = 1`
* 256 colors: `FORCE_COLOR = 2`
* 16,777,216 colors: `FORCE_COLOR = 3`

Use the `NODE_DISABLE_COLORS` environment variable to enforce this function to
always return 1.
Disabling color support is also possible by using the `NO_COLOR` and
`NODE_DISABLE_COLORS` environment variables.

### writeStream.getWindowSize()
<!-- YAML
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40 changes: 39 additions & 1 deletion lib/internal/tty.js
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Expand Up @@ -72,11 +72,49 @@ const TERM_ENVS_REG_EXP = [
/^vt100/
];

function warnOnDeactivatedColors(env) {
let name;
if (env.NODE_DISABLE_COLORS !== undefined)
name = 'NODE_DISABLE_COLORS';
if (env.NO_COLOR !== undefined)
name = 'NO_COLOR';

if (name !== undefined) {
process.emitWarning(
`The '${name}' env is ignored due to the 'FORCE_COLOR' env being set.`,
'Warning'
);
}
}

// The `getColorDepth` API got inspired by multiple sources such as
// https://github.com/chalk/supports-color,
// https://github.com/isaacs/color-support.
function getColorDepth(env = process.env) {
if (env.NODE_DISABLE_COLORS || env.TERM === 'dumb') {
// Use level 0-3 to support the same levels as `chalk` does. This is done for
// consistency throughout the ecosystem.
if (env.FORCE_COLOR !== undefined) {
switch (env.FORCE_COLOR) {
case '':
case '1':
case 'true':
warnOnDeactivatedColors(env);
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Place this above the switch?

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When moved above the switch, I'll have to exclude a lot of values. That's why it's inside.

return COLORS_16;
case '2':
warnOnDeactivatedColors(env);
return COLORS_256;
case '3':
warnOnDeactivatedColors(env);
return COLORS_16m;
default:
return COLORS_2;
}
}

if (env.NODE_DISABLE_COLORS !== undefined ||
// See https://no-color.org/
env.NO_COLOR !== undefined ||
env.TERM === 'dumb') {
return COLORS_2;
}

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11 changes: 9 additions & 2 deletions test/pseudo-tty/test-tty-color-support.js
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Expand Up @@ -59,11 +59,18 @@ const writeStream = new WriteStream(fd);
[{ TERM: 'color' }, 4],
[{ TERM: 'linux' }, 4],
[{ TERM: 'fail' }, 1],
[{ NODE_DISABLE_COLORS: '1' }, 1],
[{ TERM: 'color', NODE_DISABLE_COLORS: '1' }, 1],
[{ TERM: 'dumb' }, 1],
[{ TERM: 'dumb', COLORTERM: '1' }, 1],
[{ TERM: 'terminator' }, 24],
[{ TERM: 'console' }, 4]
[{ TERM: 'console' }, 4],
[{ COLORTERM: '24bit', FORCE_COLOR: '' }, 4],
[{ NO_COLOR: '1', FORCE_COLOR: '2' }, 8],
[{ NODE_DISABLE_COLORS: '1', FORCE_COLOR: '3' }, 24],
[{ NO_COLOR: '1', COLORTERM: '24bit' }, 1],
[{ NO_COLOR: '', COLORTERM: '24bit' }, 1],
[{ TMUX: '1', FORCE_COLOR: 0 }, 1],
[{ NO_COLOR: 'true', FORCE_COLOR: 0, COLORTERM: 'truecolor' }, 1],
].forEach(([env, depth], i) => {
const actual = writeStream.getColorDepth(env);
assert.strictEqual(
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8 changes: 8 additions & 0 deletions test/pseudo-tty/test-tty-color-support.out
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@@ -0,0 +1,8 @@
(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.