Add colored status token

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

Memoization for `dev` format is collaterally removed since now `dev` format is just a string and coloring is compiled as the `status-colored` token.

resolves expressjs#171

README.md

@@ -110,13 +110,13 @@ Standard Apache common log output.
 
 ##### dev
 
-Concise output colored by response status for development use. The `:status`
+Concise output colored by response status for development use. The `:status-colored`
 token will be colored green for success codes, red for server error codes,
 yellow for client error codes, cyan for redirection codes, and uncolored
 for information codes.
 
 ```
-:method :url :status :response-time ms - :res[content-length]
+:method :url :status-colored :response-time ms - :res[content-length]
 ```
 
 ##### short
@@ -220,6 +220,18 @@ has finished being written out to the connection, in milliseconds.
 The `digits` argument is a number that specifies the number of digits to
 include on the number, defaulting to `3`, which provides microsecond precision.
 
+##### :status-colored
+
+Same as `:status` but the output will be colored red for server error codes,
+yellow for client error codes, cyan for redirection codes, green for success codes,
+and uncolored for all other codes.
+
+This token also adds a reset escape code to ensure color will only be applied to the status code. The escape code removes any existing colors in your logs that come after the `:status-colored` token. For something like a background color that's applied to the entire log string, you must add it back after the `:status-colored` token.
+
+For example, this log format sets a magenta background color to the entire log string. Notice that it's added at the beginning of the log and immediately after the `:status-colored` token.
+
+`morgan('\x1b[45m:method :url :status-colored\x1b[45m :res[content-length]\x1b[0m')`
+
 ##### :url
 
 The URL of the request. This will use `req.originalUrl` if exists, otherwise `req.url`.

index.js

@@ -47,6 +47,13 @@ var CLF_MONTH = [
 
 var DEFAULT_BUFFER_DURATION = 1000
 
+/**
+ * Placeholder that replaces empty token values in resulting log line
+ * @private
+ */
+
+var EMPTY_TOKEN_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-colored :response-time ms - :res[content-length]\x1b[0m')
 
 /**
  * request url
@@ -280,10 +264,26 @@ morgan.token('date', function getDateToken (req, res, format) {
  * response status code
  */
 
-morgan.token('status', function getStatusToken (req, res) {
- return headersSent(res)
- ? String(res.statusCode)
- : undefined
+morgan.token('status', getStatusToken)
+
+/**
+ * colored response status code
+ */
+
+morgan.token('status-colored', function getStatusColoredToken (req, res) {
+ var status = getStatusToken(req, res)
+
+ // 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 token returns color data anyway (as per tests) and
+ // value won't be eligible for substitute
+ return '\x1b[' + color + 'm' + (status || EMPTY_TOKEN_VALUE_PLACEHOLDER) + '\x1b[0m'
 })
 
 /**
@@ -404,7 +404,9 @@ function compile (format) {
  tokenArguments += ', ' + String(JSON.stringify(arg))
  }
 
- return '" +\n (' + tokenFunction + '(' + tokenArguments + ') || "-") + "'
+ return '" +\n (' +
+ tokenFunction + '(' + tokenArguments + ') || "' + EMPTY_TOKEN_VALUE_PLACEHOLDER +
+ '") + "'
  })
 
  // eslint-disable-next-line no-new-func
@@ -474,6 +476,21 @@ function getFormatFunction (name) {
  : fmt
 }
 
+/**
+ * Get value for status token
+ *
+ * @param {IncomingMessage} req
+ * @param {OutgoingMessage} res
+ * @return {string | undefined}
+ * @public
+ */
+
+function getStatusToken (req, res) {
+ return headersSent(res)
+ ? String(res.statusCode)
+ : undefined
+}
+
 /**
  * Get request IP address.
  *