fix: respect NO_COLOR environment variable in dev format

index.js

@@ -219,13 +219,19 @@ morgan.format('dev', function developmentFormatLine (tokens, req, res) {
         : status >= 200 ? 32 // green
           : 0 // no color
 
+  // respect NO_COLOR environment variable (https://no-color.org/)
+  var noColor = Boolean(process.env.NO_COLOR)
+
   // get colored function
-  var fn = developmentFormatLine[color]
+  var key = noColor ? 'plain' : color
+  var fn = developmentFormatLine[key]
 
   if (!fn) {
     // compile
-    fn = developmentFormatLine[color] = compile('\x1b[0m:method :url \x1b[' +
-      color + 'm:status\x1b[0m :response-time ms - :res[content-length]\x1b[0m')
+    fn = developmentFormatLine[key] = noColor
+      ? compile(':method :url :status :response-time ms - :res[content-length]')
+      : compile('\x1b[0m:method :url \x1b[' +
+        color + 'm:status\x1b[0m :response-time ms - :res[content-length]\x1b[0m')
   }
 
   return fn(tokens, req, res)

test/morgan.js

@@ -1333,6 +1333,20 @@ describe('morgan()', function () {
     })
 
     describe('dev', function () {
+      var noColor = process.env.NO_COLOR
+
+      beforeEach(function () {
+        delete process.env.NO_COLOR
+      })
+
+      afterEach(function () {
+        if (noColor === undefined) {
+          delete process.env.NO_COLOR
+        } else {
+          process.env.NO_COLOR = noColor
+        }
+      })
+
       it('should not color 1xx', function (done) {
         var cb = after(2, function (err, res, line) {
           if (err) return done(err)
@@ -1474,6 +1488,71 @@ describe('morgan()', function () {
             .expect(200, cb)
         })
       })
+
+      describe('with NO_COLOR environment variable', function () {
+        it('should omit ANSI color codes when NO_COLOR is set', function (done) {
+          process.env.NO_COLOR = '1'
+
+          var cb = after(2, function (err, res, line) {
+            if (err) return done(err)
+            assert.strictEqual(line.indexOf('\x1b['), -1, 'expected no ANSI codes')
+            done()
+          })
+
+          var stream = createLineStream(function (line) {
+            cb(null, null, line)
+          })
+
+          var server = createServer('dev', { stream: stream })
+
+          request(server)
+            .get('/')
+            .expect(200, cb)
+        })
+
+        it('should omit ANSI color codes for 5xx when NO_COLOR is set', function (done) {
+          process.env.NO_COLOR = '1'
+
+          var cb = after(2, function (err, res, line) {
+            if (err) return done(err)
+            assert.strictEqual(line.indexOf('\x1b['), -1, 'expected no ANSI codes')
+            done()
+          })
+
+          var stream = createLineStream(function (line) {
+            cb(null, null, line)
+          })
+
+          var server = createServer('dev', { stream: stream }, function (req, res, next) {
+            res.statusCode = 500
+            next()
+          })
+
+          request(server)
+            .get('/')
+            .expect(500, cb)
+        })
+
+        it('should preserve color when NO_COLOR is empty', function (done) {
+          process.env.NO_COLOR = ''
+
+          var cb = after(2, function (err, res, line) {
+            if (err) return done(err)
+            assert.strictEqual(line.substr(0, 37), '_color_0_GET / _color_32_200_color_0_')
+            done()
+          })
+
+          var stream = createColorLineStream(function onLine (line) {
+            cb(null, null, line)
+          })
+
+          var server = createServer('dev', { stream: stream })
+
+          request(server)
+            .get('/')
+            .expect(200, cb)
+        })
+      })
     })
 
     describe('short', function () {