Add coloring option for status token

Coloring status makes sense for whatever format user wants, not just the internal `dev` one. So using `:status[color]` gives that ability.

As for collaterally removed memoization for `dev` format, well, wouln't it be better to memoize all formats that go through `compile`, not just the `dev` one? If that's the case, I'll do that separately.

resolves expressjs#171

index.js

@@ -47,6 +47,13 @@ var CLF_MONTH = [
 
 var DEFAULT_BUFFER_DURATION = 1000
 
+/**
+ * Placeholder that replaces empty values in resulting log line
+ * @private
+ */
+
+var EMPTY_VALUE_PLACEHOLDER = '-'
+
 /**
  * Create a logger middleware.
  *
@@ -180,30 +187,7 @@ morgan.format('tiny', ':method :url :status :res[content-length] - :response-tim
  * dev (colored)
  */
 
-morgan.format('dev', function developmentFormatLine (tokens, req, res) {
- // get the status code if response written
- var status = headersSent(res)
- ? res.statusCode
- : undefined
-
- // get status color
- var color = status >= 500 ? 31 // red
- : status >= 400 ? 33 // yellow
- : status >= 300 ? 36 // cyan
- : status >= 200 ? 32 // green
- : 0 // no color
-
- // get colored function
- var fn = developmentFormatLine[color]
-
- 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')
- }
-
- return fn(tokens, req, res)
-})
+morgan.format('dev', '\x1b[0m:method :url :status[color] \x1b[0m:response-time ms - :res[content-length]\x1b[0m')
 
 /**
  * request url
@@ -260,10 +244,25 @@ morgan.token('date', function getDateToken (req, res, format) {
  * response status code
  */
 
-morgan.token('status', function getStatusToken (req, res) {
- return headersSent(res)
+morgan.token('status', function getStatusToken (req, res, format) {
+ var status = headersSent(res)
  ? String(res.statusCode)
  : undefined
+
+ if (format === 'color') {
+ // get status color
+ var color = status >= 500 ? 31 // red
+ : status >= 400 ? 33 // yellow
+ : status >= 300 ? 36 // cyan
+ : status >= 200 ? 32 // green
+ : 0 // no color
+
+ // using placeholder here since `compile` adds it if token function returns falsy,
+ // but this coloring branch returns color data anyway and value won't be eligible for substitute
+ return '\x1b[' + color + 'm' + (status || EMPTY_VALUE_PLACEHOLDER)
+ }
+
+ return status
 })
 
 /**
@@ -384,7 +383,9 @@ function compile (format) {
  tokenArguments += ', ' + String(JSON.stringify(arg))
  }
 
- return '" +\n (' + tokenFunction + '(' + tokenArguments + ') || "-") + "'
+ return '" +\n (' +
+ tokenFunction + '(' + tokenArguments + ') || "' + EMPTY_VALUE_PLACEHOLDER +
+ '") + "'
  }) + '"'
 
  // eslint-disable-next-line no-new-func