fix(test): make evalModule faster by caching spawned modules in the browser

karma-dart-evalcache.js

@@ -0,0 +1,86 @@
+// This module provides a customFileHandler for karma
+// that serves files with urls like /packages_<timestamp>/...
+// with maximum cache.
+// We are using these urls when we spawn isolates
+// so that the isolates don't reload files every time.
+
+var common = require('karma/lib/middleware/common');
+var fs = require('fs');
+
+var DART_EVAL_PATH_RE = /.*\/packages_\d+\/(.*)$/;
+
+module.exports = createFactory;
+
+function createFactory(proxyPaths) {
+  return {
+    'framework:dart-evalcache': ['factory', dartEvalCacheFactory]
+  };
+
+  function dartEvalCacheFactory(emitter, logger, customFileHandlers) {
+    var filesPromise = new common.PromiseContainer();
+    emitter.on('file_list_modified', function(files) {
+      filesPromise.set(files);
+    });
+
+    var serveFile = common.createServeFile(fs);
+    var log = logger.create('dart-evalcache');
+
+    customFileHandlers.push({
+      urlRegex: DART_EVAL_PATH_RE,
+      handler: handler
+    });
+
+    // See source_files handler
+    function handler(request, response, fa, fb, basePath) {
+      return filesPromise.then(function(files) {
+        try {
+          var requestedFilePath = mapUrlToFile(request.url, proxyPaths, basePath, log);
+          // TODO(vojta): change served to be a map rather then an array
+          var file = findByPath(files.served, requestedFilePath);
+          if (file) {
+            serveFile(file.contentPath || file.path, response, function() {
+              common.setHeavyCacheHeaders(response);
+            }, file.content);
+          } else {
+            response.writeHead(404);
+            response.end('Not found');
+          }
+        } catch (e) {
+          log.error(e.stack);
+          response.writeHead(500);
+          response.end('Error', e.stack);
+        }
+      });
+    }
+  };
+}
+
+function mapUrlToFile(url, proxyPaths, basePath, log) {
+  var originalUrl = url;
+  url = url.indexOf('?') > -1 ? url.substring(0, url.indexOf('?')) : url;
+  var match = DART_EVAL_PATH_RE.exec(url);
+  var packagePath = match[1];
+  var result = null;
+  var lastProxyFromLength = 0;
+  Object.keys(proxyPaths).forEach(function(proxyFrom) {
+    if (startsWith(packagePath, proxyFrom) && proxyFrom.length > lastProxyFromLength) {
+      lastProxyFromLength = proxyFrom.length;
+      result = proxyPaths[proxyFrom] + packagePath.substring(proxyFrom.length);
+    }
+  });
+  return basePath + '/' + result;
+}
+
+function startsWith(string, subString) {
+  return string.length >= subString.length && string.slice(0, subString.length) === subString;
+}
+
+function findByPath(files, path) {
+  for (var i = 0; i < files.length; i++) {
+    if (files[i].path === path) {
+      return files[i];
+    }
+  }
+
+  return null;
+}