Merge pull request #2 from nomcopter/optimize-relate-context-performance

fix: optimize contextNormalPath mzgoddard#469

lib/util/relate-context.js

@@ -76,23 +76,39 @@ const relateNormalPathSet = (exports.relateNormalPathSet = function relateNormal
  *
  */
 
+// Cache whether we need to replace path.sep because contextNormalPath is called _very_ frequently
+const resolveRelativeCompilerContext =
+  '/' === path.sep
+    ? function(context, key) {
+        return path.resolve(context, key);
+      }
+    : function(context, key) {
+        return path.resolve(context, key).replace(/\//g, path.sep);
+      };
+
 const contextNormalPath = (exports.contextNormalPath = function contextNormalPath(
   compiler,
   key,
 ) {
-  if (typeof key !== 'string') {
+  if (typeof key !== 'string' || key === '') {
     return key;
   }
+
+  const context = compilerContext(compiler);
   if (key === '.') {
-    return compilerContext(compiler);
+    return context;
   }
-  if (key === '') {
-    return '';
+
+  const markIndex = key.indexOf('?');
+  if (markIndex === -1) {
+    return resolveRelativeCompilerContext(context, key);
   }
-  const abs = path.resolve(compilerContext(compiler), key.split('?')[0]);
-  return [abs.replace(/\//g, path.sep)]
-    .concat(key.split('?').slice(1))
-    .join('?');
+
+  const abs = resolveRelativeCompilerContext(
+    context,
+    key.substring(0, markIndex),
+  );
+  return abs + '?' + key.substring(markIndex + 1);
 });
 
 const contextNormalRequest = (exports.contextNormalRequest = function contextNormalRequest(