feat: NO_COLOR env var removes color in dev format

README.md

@@ -168,6 +168,11 @@ for information codes.
 GET /dev 200 0.224 ms - 2
 ```
 
+Coloring is disabled when the [`NO_COLOR`](https://no-color.org) environment
+variable is set to any non-empty value, in which case the output above is
+written without any escape sequences. The variable is read once, when `morgan`
+is first required.
+
 ##### short
 
 Shorter than default, also including response time.

index.js

@@ -47,6 +47,8 @@ var CLF_MONTH = [
 
 var DEFAULT_BUFFER_DURATION = 1000
 
+var NO_COLOR = Boolean(process.env.NO_COLOR)
+
 /**
  * Escape control characters and backslashes so a value is safe for
  * line-oriented logs.
@@ -235,6 +237,12 @@ morgan.format('dev', function developmentFormatLine (tokens, req, res) {
   return fn(tokens, req, res)
 })
 
+// NO_COLOR (https://no-color.org): when set and not an empty string, the dev
+// format is replaced at load time with a variant free of escape sequences
+if (NO_COLOR) {
+  morgan.format('dev', compile(':method :url :status :response-time ms - :res[content-length]'))
+}
+
 /**
  * request url
  */

package.json

@@ -48,7 +48,7 @@
   },
   "scripts": {
     "lint": "eslint --plugin markdown --ext js,md .",
-    "test": "mocha --check-leaks --reporter spec",
+    "test": "mocha --check-leaks --reporter spec test/morgan.js && mocha --check-leaks --reporter spec test/noColor.js",
     "test-ci": "nyc --reporter=lcov --reporter=text npm test",
     "test-cov": "nyc --reporter=html --reporter=text npm test"
   }

test/morgan.js

@@ -1,5 +1,8 @@
 
 process.env.NO_DEPRECATION = 'morgan'
+// empty, not deleted: per https://no-color.org an empty NO_COLOR must not
+// disable color, so the dev tests below guard that. Set: test/noColor.js
+process.env.NO_COLOR = ''
 
 var assert = require('assert')
 var fs = require('fs')

test/noColor.js

@@ -0,0 +1,206 @@
+
+process.env.NO_DEPRECATION = 'morgan'
+// read once at require time, hence a separate file from test/morgan.js.
+// '0' is deliberate: any non-empty value disables color, whatever it is
+process.env.NO_COLOR = '0'
+
+var assert = require('assert')
+var http = require('http')
+var morgan = require('..')
+var request = require('supertest')
+var split = require('split')
+
+describe('morgan()', function () {
+  describe('formats', function () {
+    describe('dev', function () {
+      it('should not color 1xx', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assertPlainDevLine(line, 102)
+          done()
+        })
+
+        var stream = createLineStream(function onLine (line) {
+          cb(null, null, line)
+        })
+
+        var server = createServer('dev', { stream: stream }, function (req, res, next) {
+          res.statusCode = 102
+          next()
+        })
+
+        request(server)
+          .get('/')
+          .expect(102, function (err, res) {
+            if (err && err.code === 'ECONNRESET') {
+              // finishing response with 1xx is invalid http
+              // but node.js server lets the server do this, so
+              // morgan needs to test in this condition even if
+              // the http client doesn't like it
+              err = null
+            }
+            cb(err, res)
+          })
+      })
+
+      it('should not color 2xx', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assertPlainDevLine(line, 200)
+          done()
+        })
+
+        var stream = createLineStream(function onLine (line) {
+          cb(null, null, line)
+        })
+
+        var server = createServer('dev', { stream: stream }, function (req, res, next) {
+          res.statusCode = 200
+          next()
+        })
+
+        request(server)
+          .get('/')
+          .expect(200, cb)
+      })
+
+      it('should not color 3xx', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assertPlainDevLine(line, 300)
+          done()
+        })
+
+        var stream = createLineStream(function onLine (line) {
+          cb(null, null, line)
+        })
+
+        var server = createServer('dev', { stream: stream }, function (req, res, next) {
+          res.statusCode = 300
+          next()
+        })
+
+        request(server)
+          .get('/')
+          .expect(300, cb)
+      })
+
+      it('should not color 4xx', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assertPlainDevLine(line, 400)
+          done()
+        })
+
+        var stream = createLineStream(function onLine (line) {
+          cb(null, null, line)
+        })
+
+        var server = createServer('dev', { stream: stream }, function (req, res, next) {
+          res.statusCode = 400
+          next()
+        })
+
+        request(server)
+          .get('/')
+          .expect(400, cb)
+      })
+
+      it('should not color 5xx', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assertPlainDevLine(line, 500)
+          done()
+        })
+
+        var stream = createLineStream(function onLine (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 match the documented dev format', function (done) {
+        var cb = after(2, function (err, res, line) {
+          if (err) return done(err)
+          assert.ok(/^GET \/ 200 \d+\.\d{3} ms - -$/.test(line),
+            'unexpected line ' + JSON.stringify(line))
+          done()
+        })
+
+        var stream = createLineStream(function onLine (line) {
+          cb(null, null, line)
+        })
+
+        request(createServer('dev', { stream: stream }))
+          .get('/')
+          .expect(200, cb)
+      })
+    })
+  })
+})
+
+function after (count, callback) {
+  var args = new Array(3)
+  var i = 0
+
+  return function (err, arg1, arg2) {
+    assert.ok(i++ < count, 'callback called ' + count + ' times')
+
+    args[0] = args[0] || err
+    args[1] = args[1] || arg1
+    args[2] = args[2] || arg2
+
+    if (count === i) {
+      callback.apply(null, args)
+    }
+  }
+}
+
+function assertPlainDevLine (line, status) {
+  assert.strictEqual(line.indexOf('\x1b'), -1, 'expected no escapes in ' + JSON.stringify(line))
+  assert.ok(
+    new RegExp('^GET / ' + status + ' \\d+\\.\\d{3} ms - (\\d+|-)$').test(line),
+    'unexpected line ' + JSON.stringify(line)
+  )
+}
+
+function createLineStream (callback) {
+  return split().on('data', callback)
+}
+
+function createServer (format, opts, fn, fn1) {
+  var logger = morgan(format, opts)
+  var middle = fn || noopMiddleware
+
+  return http.createServer().on('request', function onRequest (req, res) {
+    // prior alterations
+    if (fn1) {
+      fn1(req, res)
+    }
+
+    logger(req, res, function onNext (err) {
+      // allow req, res alterations
+      middle(req, res, function onDone () {
+        if (err) {
+          res.statusCode = 500
+          res.end(err.message)
+        }
+
+        res.setHeader('X-Sent', 'true')
+        res.end((req.connection && req.connection.remoteAddress) || '-')
+      })
+    })
+  })
+}
+
+function noopMiddleware (req, res, next) {
+  next()
+}