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tty: add NO_COLOR and FORCE_COLOR support
This adds support to enforce a specific color depth by checking the `FORCE_COLOR` environment variable similar to `chalk`. On top of that we also add support for the `NO_COLOR` environment variable as suggested by https://no-color.org/. PR-URL: #26485 Refs: #26248 Reviewed-By: Roman Reiss <[email protected]> Reviewed-By: Jeremiah Senkpiel <[email protected]>
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Lines changed: 70 additions & 9 deletions

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‎doc/api/tty.md‎

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@@ -144,8 +144,9 @@ position.
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added: v9.9.0
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-->
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* `env` {Object} An object containing the environment variables to check.
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**Default:** `process.env`.
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* `env` {Object} An object containing the environment variables to check. This
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enables simulating the usage of a specific terminal. **Default:**
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`process.env`.
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* Returns: {number}
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Returns:
@@ -159,11 +160,18 @@ Use this to determine what colors the terminal supports. Due to the nature of
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colors in terminals it is possible to either have false positives or false
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negatives. It depends on process information and the environment variables that
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may lie about what terminal is used.
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To enforce a specific behavior without relying on `process.env` it is possible
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to pass in an object with different settings.
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It is possible to pass in an `env` object to simulate the usage of a specific
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terminal. This can be useful to check how specific environment settings behave.
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To enforce a specific color support, use one of the below environment settings.
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* 2 colors: `FORCE_COLOR = 0` (Disables colors)
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* 16 colors: `FORCE_COLOR = 1`
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* 256 colors: `FORCE_COLOR = 2`
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* 16,777,216 colors: `FORCE_COLOR = 3`
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Use the `NODE_DISABLE_COLORS` environment variable to enforce this function to
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always return 1.
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Disabling color support is also possible by using the `NO_COLOR` and
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`NODE_DISABLE_COLORS` environment variables.
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### writeStream.getWindowSize()
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<!-- YAML

‎lib/internal/tty.js‎

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@@ -72,11 +72,49 @@ const TERM_ENVS_REG_EXP = [
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/^vt100/
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];
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function warnOnDeactivatedColors(env) {
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let name;
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if (env.NODE_DISABLE_COLORS !== undefined)
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name = 'NODE_DISABLE_COLORS';
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if (env.NO_COLOR !== undefined)
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name = 'NO_COLOR';
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if (name !== undefined) {
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process.emitWarning(
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`The '${name}' env is ignored due to the 'FORCE_COLOR' env being set.`,
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'Warning'
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);
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}
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}
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// The `getColorDepth` API got inspired by multiple sources such as
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// https://github.com/chalk/supports-color,
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// https://github.com/isaacs/color-support.
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function getColorDepth(env = process.env) {
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if (env.NODE_DISABLE_COLORS || env.TERM === 'dumb') {
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// Use level 0-3 to support the same levels as `chalk` does. This is done for
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// consistency throughout the ecosystem.
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if (env.FORCE_COLOR !== undefined) {
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switch (env.FORCE_COLOR) {
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case '':
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case '1':
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case 'true':
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warnOnDeactivatedColors(env);
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return COLORS_16;
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case '2':
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warnOnDeactivatedColors(env);
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return COLORS_256;
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case '3':
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warnOnDeactivatedColors(env);
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return COLORS_16m;
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default:
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return COLORS_2;
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}
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}
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if (env.NODE_DISABLE_COLORS !== undefined ||
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// See https://no-color.org/
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env.NO_COLOR !== undefined ||
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env.TERM === 'dumb') {
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return COLORS_2;
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}
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‎test/pseudo-tty/test-tty-color-support.js‎

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@@ -59,11 +59,18 @@ const writeStream = new WriteStream(fd);
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[{ TERM: 'color' }, 4],
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[{ TERM: 'linux' }, 4],
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[{ TERM: 'fail' }, 1],
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[{ NODE_DISABLE_COLORS: '1' }, 1],
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[{ TERM: 'color', NODE_DISABLE_COLORS: '1' }, 1],
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[{ TERM: 'dumb' }, 1],
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[{ TERM: 'dumb', COLORTERM: '1' }, 1],
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[{ TERM: 'terminator' }, 24],
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[{ TERM: 'console' }, 4]
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[{ TERM: 'console' }, 4],
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[{ COLORTERM: '24bit', FORCE_COLOR: '' }, 4],
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[{ NO_COLOR: '1', FORCE_COLOR: '2' }, 8],
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[{ NODE_DISABLE_COLORS: '1', FORCE_COLOR: '3' }, 24],
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[{ NO_COLOR: '1', COLORTERM: '24bit' }, 1],
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[{ NO_COLOR: '', COLORTERM: '24bit' }, 1],
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[{ TMUX: '1', FORCE_COLOR: 0 }, 1],
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[{ NO_COLOR: 'true', FORCE_COLOR: 0, COLORTERM: 'truecolor' }, 1],
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].forEach(([env, depth], i) => {
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const actual = writeStream.getColorDepth(env);
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assert.strictEqual(

‎test/pseudo-tty/test-tty-color-support.out‎

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(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
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(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.

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