A start at standardising error handling

lib/errors.js

@@ -0,0 +1,102 @@
+function middleware (env, config) {
+  return function(err, req, res, next) {
+    if (req.xhr)
+      return res.json(err);
+
+    var templates = [
+      err.status,
+      err.code,
+      Unknown.status,
+      Unknown.code
+    ];
+
+    templates.forEach(function(item, index, list) {
+      var templateName = (''+item)
+        .replace(/\s+/g, '-')
+        .toLowerCase();
+      list[index] = './errors/' + templateName + '.html';
+    });
+
+    function render (template) {
+      if (!template)
+        return res.send(err);
+
+      try {
+        template = env.getTemplate(template);
+        res.status(err.status);
+        res.send(template.render({error: err}));
+      } catch (e) {
+        if (e.name === 'Template render error')
+          console.log('Error rendering template:', template.path);
+        render(templates.shift());
+      }
+    }
+
+    render(templates.shift());
+  }
+}
+
+module.exports = function (app, env, config) {
+  // Generate a 404 - if we've got this far, the page doesn't exist
+  app.use(function(req, res, next) {
+    next(new NotFound(req.url));
+  })
+
+  // It would be nice not to have to pass env around, but it doesn't
+  // seem to be available through `app`, and there doesn't seem to be
+  // a nice way of catching a failed template rendering attempt.
+  app.use(middleware(env, config));
+}
+
+var register = {};
+
+function createExceptionType (name, code) {
+  if (!code) code = 500;
+
+  var status = name
+    .replace(/\s+/g, ' ')
+    .replace(/(^\s+|\s+$)/g, '')
+    .replace(/\w[A-Z]/g, function(m) { return m[0] + ' ' + m[1]; });
+
+  function Exception (msg) {
+    this.name = name;
+    this.status = status;
+    this.code = code;
+    this.message = msg || status;
+    Error.call(this, this.message);
+    Error.captureStackTrace(this, arguments.callee);
+  }
+
+  Exception.prototype = new Error();
+  Exception.prototype.constructor = Exception;
+  Exception.prototype.toString = function () {
+    return '[' + this.name + ' Exception: ' + this.message + ']';
+  }
+
+  register[code] = Exception;
+
+  return Exception;
+}
+
+var BadRequest = createExceptionType('BadRequest', 400);
+var Unauthorized = createExceptionType('Unauthorized', 401);
+var Forbidden = createExceptionType('Forbidden', 403);
+var NotFound = createExceptionType('NotFound', 404);
+var Unknown = createExceptionType('Internal', 500);
+var NotImplemented = createExceptionType('NotImplemented', 501);
+var BadGateway = createExceptionType('BadGateway', 502);
+
+module.exports.BadRequest = BadRequest;
+module.exports.Unauthorized = Unauthorized;
+module.exports.Forbidden = Forbidden;
+module.exports.NotFound = NotFound;
+module.exports.Unknown = Unknown;
+module.exports.NotImplemented = NotImplemented;
+module.exports.BadGateway = BadGateway;
+
+module.exports.lookup = function lookup (code) {
+  if (!register[code])
+    code = 500;
+
+  return register[code];
+};

views/errors/404.html

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+{% extends 'errors/layout.html' %}
+{% set pageTitle = 'Page not found' %}
+
+{% block content %}
+<p>The page you seem to be looking for doesn't exist.</p>
+{% endblock %}

views/errors/500.html

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+{% extends 'errors/layout.html' %}
+{% set pageTitle = 'Server error' %}
+
+{% block content %}
+<pre>{{ error }}</pre>
+{% endblock %}

views/errors/layout.html

@@ -0,0 +1 @@
+{% extends 'layout.html' %}