tty: add getColorDepth function

Right now it is very difficult to determine if a terminal supports colors or not. This function adds this functionality by detecting environment variables and checking process. Backport-PR-URL: #19230 PR-URL: #17615 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

Author: BridgeAR

doc/api/assert.md

@@ -65,6 +65,9 @@ AssertionError [ERR_ASSERTION]: Input A expected to deepStrictEqual input B:
  ]
 ```
 
+To deactivate the colors, use the `NODE_DISABLE_COLORS` environment variable.
+Please note that this will also deactivate the colors in the REPL.
+
 ## Legacy mode
 
 > Stability: 0 - Deprecated: Use strict mode instead.

doc/api/tty.md

@@ -121,6 +121,32 @@ added: v0.7.7
 A `number` specifying the number of rows the TTY currently has. This property
 is updated whenever the `'resize'` event is emitted.
 
+### writeStream.getColorDepth([env])
+<!-- YAML
+added: REPLACEME
+-->
+
+*`env`{object} A object containing the environment variables to check.
+ Defaults to `process.env`.
+* Returns:{number}
+
+Returns:
+* 1 for 2,
+* 4 for 16,
+* 8 for 256,
+* 24 for 16,777,216
+colors supported.
+
+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.
+
+Use the `NODE_DISABLE_COLORS` environment variable to enforce this function to
+always return 1.
+
 ## tty.isatty(fd)
 <!-- YAML
 added: v0.5.8

lib/internal/errors.js

@@ -13,6 +13,10 @@
 constkCode=Symbol('code');
 constmessages=newMap();
 
+vargreen='';
+varred='';
+varwhite='';
+
 const{
 UV_EAI_MEMORY,
 UV_EAI_NODATA,
@@ -90,7 +94,7 @@ function createErrDiff(actual, expected, operator){
 constexpectedLines=util
 .inspect(expected,{compact: false}).split('\n');
 constmsg=`Input A expected to ${operator} input B:\n`+
-'\u001b[32m+ expected\u001b[39m \u001b[31m- actual\u001b[39m';
+`${green}+ expected${white}${red}- actual${white}`;
 constskippedMsg=' ... Lines skipped';
 
 // Remove all ending lines that match (this optimizes the output for
@@ -136,7 +140,7 @@ function createErrDiff(actual, expected, operator){
 printedLines++;
 }
 lastPos=i;
-other+=`\n\u001b[32m+\u001b[39m${expectedLines[i]}`;
+other+=`\n${green}+${white}${expectedLines[i]}`;
 printedLines++;
 // Only extra actual lines exist
 }elseif(expectedLines.length<i+1){
@@ -152,7 +156,7 @@ function createErrDiff(actual, expected, operator){
 printedLines++;
 }
 lastPos=i;
-res+=`\n\u001b[31m-\u001b[39m${actualLines[i]}`;
+res+=`\n${red}-${white}${actualLines[i]}`;
 printedLines++;
 // Lines diverge
 }elseif(actualLines[i]!==expectedLines[i]){
@@ -168,8 +172,8 @@ function createErrDiff(actual, expected, operator){
 printedLines++;
 }
 lastPos=i;
-res+=`\n\u001b[31m-\u001b[39m${actualLines[i]}`;
-other+=`\n\u001b[32m+\u001b[39m${expectedLines[i]}`;
+res+=`\n${red}-${white}${actualLines[i]}`;
+other+=`\n${green}+${white}${expectedLines[i]}`;
 printedLines+=2;
 // Lines are identical
 }else{
@@ -205,6 +209,13 @@ class AssertionError extends Error{
 if(message!=null){
 super(message);
 }else{
+if(util_===null&&
+process.stdout.isTTY&&
+process.stdout.getColorDepth()!==1){
+green='\u001b[32m';
+white='\u001b[39m';
+red='\u001b[31m';
+}
 constutil=lazyUtil();
 if(actual&&actual.stack&&actualinstanceofError)
 actual=`${actual.name}: ${actual.message}`;

lib/tty.js

@@ -26,6 +26,14 @@ const net = require('net');
 const{TTY, isTTY }=process.binding('tty_wrap');
 consterrors=require('internal/errors');
 constreadline=require('readline');
+const{ release }=require('os');
+
+constOSRelease=release().split('.');
+
+constCOLORS_2=1;
+constCOLORS_16=4;
+constCOLORS_256=8;
+constCOLORS_16m=24;
 
 functionisatty(fd){
 returnNumber.isInteger(fd)&&fd>=0&&isTTY(fd);
@@ -90,6 +98,70 @@ inherits(WriteStream, net.Socket);
 
 WriteStream.prototype.isTTY=true;
 
+WriteStream.prototype.getColorDepth=function(env=process.env){
+if(env.NODE_DISABLE_COLORS||env.TERM==='dumb'&&!env.COLORTERM){
+returnCOLORS_2;
+}
+
+if(process.platform==='win32'){
+// Windows 10 build 10586 is the first Windows release that supports 256
+// colors. Windows 10 build 14931 is the first release that supports
+// 16m/TrueColor.
+if(+OSRelease[0]>=10){
+constbuild=+OSRelease[2];
+if(build>=14931)
+returnCOLORS_16m;
+if(build>=10586)
+returnCOLORS_256;
+}
+
+returnCOLORS_16;
+}
+
+if(env.TMUX){
+returnCOLORS_256;
+}
+
+if(env.CI){
+if('TRAVIS'inenv||'CIRCLECI'inenv||'APPVEYOR'inenv||
+'GITLAB_CI'inenv||env.CI_NAME==='codeship'){
+returnCOLORS_256;
+}
+returnCOLORS_2;
+}
+
+if('TEAMCITY_VERSION'inenv){
+return/^(9\.(0*[1-9]\d*)\.|\d{2,}\.)/.test(env.TEAMCITY_VERSION) ?
+COLORS_16 : COLORS_2;
+}
+
+switch(env.TERM_PROGRAM){
+case'iTerm.app':
+if(!env.TERM_PROGRAM_VERSION||
+/^[0-2]\./.test(env.TERM_PROGRAM_VERSION)){
+returnCOLORS_256;
+}
+returnCOLORS_16m;
+case'HyperTerm':
+case'Hyper':
+case'MacTerm':
+returnCOLORS_16m;
+case'Apple_Terminal':
+returnCOLORS_256;
+}
+
+if(env.TERM){
+if(/^xterm-256/.test(env.TERM))
+returnCOLORS_256;
+if(/^screen|^xterm|^vt100|color|ansi|cygwin|linux/i.test(env.TERM))
+returnCOLORS_16;
+}
+
+if(env.COLORTERM)
+returnCOLORS_16;
+
+returnCOLORS_2;
+};
 
 WriteStream.prototype._refreshSize=function(){
 varoldCols=this.columns;

test/parallel/test-assert.js

@@ -763,10 +763,13 @@ common.expectsError(
 );
 
 // Test error diffs
+constcolors=process.stdout.isTTY&&process.stdout.getColorDepth()>1;
 conststart='Input A expected to deepStrictEqual input B:';
-constactExp='\u001b[32m+ expected\u001b[39m \u001b[31m- actual\u001b[39m';
-constplus='\u001b[32m+\u001b[39m';
-constminus='\u001b[31m-\u001b[39m';
+constactExp=colors ?
+'\u001b[32m+ expected\u001b[39m \u001b[31m- actual\u001b[39m' :
+'+ expected - actual';
+constplus=colors ? '\u001b[32m+\u001b[39m' : '+';
+constminus=colors ? '\u001b[31m-\u001b[39m' : '-';
 letmessage=[
 start,
 `${actExp} ... Lines skipped`,

test/parallel/test-tty-get-color-depth.js

@@ -0,0 +1,52 @@
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert').strict;
+/* eslint-disable no-restricted-properties */
+const{ openSync }=require('fs');
+consttty=require('tty');
+
+const{ WriteStream }=require('tty');
+
+// Do our best to grab a tty fd.
+functiongetTTYfd(){
+constttyFd=[0,1,2,4,5].find(tty.isatty);
+if(ttyFd===undefined){
+try{
+returnopenSync('/dev/tty');
+}catch(e){
+// There aren't any tty fd's available to use.
+return-1;
+}
+}
+returnttyFd;
+}
+
+constfd=getTTYfd();
+
+// Give up if we did not find a tty
+if(fd===-1)
+common.skip();
+
+constwriteStream=newWriteStream(fd);
+
+letdepth=writeStream.getColorDepth();
+
+assert.equal(typeofdepth,'number');
+assert(depth>=1&&depth<=24);
+
+// If the terminal does not support colors, skip the rest
+if(depth===1)
+common.skip();
+
+assert.notEqual(writeStream.getColorDepth({TERM: 'dumb'}),depth);
+
+// Deactivate colors
+consttmp=process.env.NODE_DISABLE_COLORS;
+process.env.NODE_DISABLE_COLORS=1;
+
+depth=writeStream.getColorDepth();
+
+assert.equal(depth,1);
+
+process.env.NODE_DISABLE_COLORS=tmp;