Allow setting support level with FORCE_COLOR environment variable (#85)

index.js

@@ -8,15 +8,23 @@ let forceColor;
 if (hasFlag('no-color') ||
 	hasFlag('no-colors') ||
 	hasFlag('color=false')) {
-	forceColor = false;
+	forceColor = 0;
 } else if (hasFlag('color') ||
 	hasFlag('colors') ||
 	hasFlag('color=true') ||
 	hasFlag('color=always')) {
-	forceColor = true;
+	forceColor = 1;
 }
 if ('FORCE_COLOR' in env) {
-	forceColor = env.FORCE_COLOR.length === 0 || parseInt(env.FORCE_COLOR, 10) !== 0;
+	if (env.FORCE_COLOR === true || env.FORCE_COLOR === 'true') {
+		forceColor = 1;
+	} else if (env.FORCE_COLOR === false || env.FORCE_COLOR === 'false') {
+		forceColor = 0;
+	} else {
+		forceColor = env.FORCE_COLOR.length === 0 ?
+			1 :
+      Math.min(parseInt(env.FORCE_COLOR, 10), 3);
+	}
 }
 
 function translateLevel(level) {
@@ -33,7 +41,7 @@ function translateLevel(level) {
 }
 
 function supportsColor(stream) {
-	if (forceColor === false) {
+	if (forceColor === 0) {
 		return 0;
 	}
 
@@ -47,11 +55,11 @@ function supportsColor(stream) {
 		return 2;
 	}
 
-	if (stream && !stream.isTTY && forceColor !== true) {
+	if (stream && !stream.isTTY && forceColor === undefined) {
 		return 0;
 	}
 
-	const min = forceColor ? 1 : 0;
+	const min = forceColor || 0;
 
 	if (env.TERM === 'dumb') {
 		return min;

test.js

@@ -325,6 +325,54 @@ test('return level 2 when FORCE_COLOR is set when not TTY in xterm256', t => {
 	t.is(result.stdout.level, 2);
 });
 
+test('supports setting a color level using FORCE_COLOR', t => {
+	let result;
+	process.env.FORCE_COLOR = '1';
+	result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 1);
+
+	process.env.FORCE_COLOR = '2';
+	result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 2);
+
+	process.env.FORCE_COLOR = '3';
+	result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 3);
+
+	process.env.FORCE_COLOR = '0';
+	result = importFresh('.');
+	t.false(result.stdout);
+});
+
+test('FORCE_COLOR maxes out at a value of 3', t => {
+	process.env.FORCE_COLOR = '4';
+	const result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 3);
+});
+
+test('FORCE_COLOR works when set via command line (all values are strings)', t => {
+	let result;
+	process.env.FORCE_COLOR = 'true';
+	result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 1);
+
+	process.stdout.isTTY = false;
+	process.env.FORCE_COLOR = 'true';
+	process.env.TERM = 'xterm-256color';
+	result = importFresh('.');
+	t.truthy(result.stdout);
+	t.is(result.stdout.level, 2);
+
+	process.env.FORCE_COLOR = 'false';
+	result = importFresh('.');
+	t.false(result.stdout);
+});
+
 test('return false when `TERM` is set to dumb', t => {
 	process.env.TERM = 'dumb';
 	const result = importFresh('.');