From af0b1387830ec946240bd1d661d514fcbe3b9198 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Thu, 7 Mar 2019 01:48:02 +0100
Subject: [PATCH 1/2] 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/.
---
 doc/api/tty.md                             | 20 +++++++----
 lib/internal/tty.js                        | 40 +++++++++++++++++++++-
 test/pseudo-tty/test-tty-color-support.js  | 11 ++++--
 test/pseudo-tty/test-tty-color-support.out |  8 +++++
 4 files changed, 70 insertions(+), 9 deletions(-)

diff --git a/doc/api/tty.md b/doc/api/tty.md
index 12a34b14eb7cc0..c2e9371f2ff74e 100644
--- a/doc/api/tty.md
+++ b/doc/api/tty.md
@@ -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:
@@ -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
diff --git a/lib/internal/tty.js b/lib/internal/tty.js
index 486dbbeaa508d3..9c34d3fdb7f950 100644
--- a/lib/internal/tty.js
+++ b/lib/internal/tty.js
@@ -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);
+        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;
   }
 
diff --git a/test/pseudo-tty/test-tty-color-support.js b/test/pseudo-tty/test-tty-color-support.js
index b5bc3aca247417..b2cfc804c30281 100644
--- a/test/pseudo-tty/test-tty-color-support.js
+++ b/test/pseudo-tty/test-tty-color-support.js
@@ -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(
diff --git a/test/pseudo-tty/test-tty-color-support.out b/test/pseudo-tty/test-tty-color-support.out
index e69de29bb2d1d6..f73fbdcd9651f6 100644
--- a/test/pseudo-tty/test-tty-color-support.out
+++ b/test/pseudo-tty/test-tty-color-support.out
@@ -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.

From 8708e7ecca92974ba2378855f55348858b7097c5 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Fri, 8 Mar 2019 17:11:41 +0100
Subject: [PATCH 2/2] fixup! tty: add NO_COLOR and FORCE_COLOR support

---
 doc/api/tty.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/doc/api/tty.md b/doc/api/tty.md
index c2e9371f2ff74e..4edc3ad86e11d5 100644
--- a/doc/api/tty.md
+++ b/doc/api/tty.md
@@ -165,10 +165,10 @@ 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
+* 2 colors: `FORCE_COLOR = 0` (Disables colors)
+* 16 colors: `FORCE_COLOR = 1`
+* 256 colors: `FORCE_COLOR = 2`
+* 16,777,216 colors: `FORCE_COLOR = 3`
 
 Disabling color support is also possible by using the `NO_COLOR` and
 `NODE_DISABLE_COLORS` environment variables.