return error if interpreter does not exit with 0

gateway.js

@@ -19,7 +19,11 @@ module.exports = function cgi(docroot, options) {
       , path = url.pathname
       , handler = options[extname(path)]
 
-    if (!next) next = function() { res.end() }
+    if (!next) next = function(err) {
+      if (err) res.writeHead(500, err)
+      res.end()
+    }
+
     if (!handler) return next()
 
     var script = normalize(join(docroot, path))
@@ -109,7 +113,10 @@ module.exports = function cgi(docroot, options) {
         }
       }
     })
-    child.on('close', res.end)
+    child.on('exit', function(code) {
+      if (code === 0) return res.end()
+      next(handler + ' exited with code ' + code)
+    })
   }
 
 }

test/index.js

@@ -1,7 +1,10 @@
 var gateway = require('../gateway')
   , http = require('http')
   , request = require('supertest')
-  , app = http.createServer(gateway(__dirname))
+  , app = http.createServer(gateway(__dirname, {
+    '.php': 'php-cgi',
+    '.foo': __dirname + '/non-existing-interpreter'
+  }))
 
 describe('gateway()', function() {
   it('should pass on the query string', function(done) {
@@ -32,4 +35,10 @@ describe('gateway()', function() {
     .expect('Plain Text Response\n')
     .end(done)
   })
+  it('should return 500 if interpreter is not found', function(done) {
+    request(app)
+    .get('/test.foo')
+    .expect(500)
+    .end(done)
+  })
 })

test/test.foo

@@ -0,0 +1 @@
+Test for invalid interpreters