feat: add path.parse implement

polyfills/path.js

@@ -23,6 +23,13 @@
 // must be no slashes, empty elements, or device names (c:\) in the array
 // (so also no leading and trailing slashes - it does not distinguish
 // relative and absolute paths)
+
+function assertPath(path) {
+  if (typeof path !== 'string') {
+    throw new TypeError('Path must be a string. Received ' + JSON.stringify(path));
+  }
+}
+
 function normalizeArray(parts, allowAboveRoot) {
   // if the path tries to go above the root, `up` ends up > 0
   var up = 0;
@@ -203,6 +210,83 @@ export function basename(path, ext) {
 export function extname(path) {
   return splitPath(path)[3];
 }
+
+export function parse(path) {
+  assertPath(path);
+
+  var ret = { root: '', dir: '', base: '', ext: '', name: '' };
+  if (path.length === 0) return ret;
+  var code = path.charCodeAt(0);
+  var isAbsolute = code === 47 /*/*/;
+  var start;
+  if (isAbsolute) {
+    ret.root = '/';
+    start = 1;
+  } else {
+    start = 0;
+  }
+  var startDot = -1;
+  var startPart = 0;
+  var end = -1;
+  var matchedSlash = true;
+  var i = path.length - 1;
+
+  // Track the state of characters (if any) we see before our first dot and
+  // after any path separator we find
+  var preDotState = 0;
+
+  // Get non-dir info
+  for (; i >= start; --i) {
+    code = path.charCodeAt(i);
+    if (code === 47 /*/*/) {
+        // If we reached a path separator that was not part of a set of path
+        // separators at the end of the string, stop now
+        if (!matchedSlash) {
+          startPart = i + 1;
+          break;
+        }
+        continue;
+      }
+    if (end === -1) {
+      // We saw the first non-path separator, mark this as the end of our
+      // extension
+      matchedSlash = false;
+      end = i + 1;
+    }
+    if (code === 46 /*.*/) {
+        // If this is our first dot, mark it as the start of our extension
+        if (startDot === -1) startDot = i;else if (preDotState !== 1) preDotState = 1;
+      } else if (startDot !== -1) {
+      // We saw a non-dot and non-path separator before our dot, so we should
+      // have a good chance at having a non-empty extension
+      preDotState = -1;
+    }
+  }
+
+  if (startDot === -1 || end === -1 ||
+  // We saw a non-dot character immediately before the dot
+  preDotState === 0 ||
+  // The (right-most) trimmed path component is exactly '..'
+  preDotState === 1 && startDot === end - 1 && startDot === startPart + 1) {
+    if (end !== -1) {
+      if (startPart === 0 && isAbsolute) ret.base = ret.name = path.slice(1, end);else ret.base = ret.name = path.slice(startPart, end);
+    }
+  } else {
+    if (startPart === 0 && isAbsolute) {
+      ret.name = path.slice(1, startDot);
+      ret.base = path.slice(1, end);
+    } else {
+      ret.name = path.slice(startPart, startDot);
+      ret.base = path.slice(startPart, end);
+    }
+    ret.ext = path.slice(startDot, end);
+  }
+
+  if (startPart > 0) ret.dir = path.slice(0, startPart - 1);else if (isAbsolute) ret.dir = '/';
+
+  return ret;
+}
+
 export default {
   extname: extname,
   basename: basename,
@@ -213,7 +297,8 @@ export default {
   join: join,
   isAbsolute: isAbsolute,
   normalize: normalize,
-  resolve: resolve
+  resolve: resolve,
+  parse: parse,
 };
 function filter (xs, f) {
     if (xs.filter) return xs.filter(f);

test/examples/path-parse.js

@@ -0,0 +1,18 @@
+import {parse} from 'path';
+
+// test path.parse
+var parseResult = parse('/home/user/dir/file.txt');
+var expectedResult = {
+  root: '/',
+  dir: '/home/user/dir',
+  base: 'file.txt',
+  ext: '.txt',
+  name: 'file'
+};
+if (Object.keys(expectedResult).every(
+    key => expectedResult[key] === parseResult[key]
+  )) {
+  done();
+} else {
+  done(new Error(`parse error, expected ${JSON.stringify(expectedResult)} but got '${JSON.stringify(parseResult)}'`));
+}

test/index.js

@@ -13,6 +13,7 @@ const files = [
   'constants.js',
   'os.js',
   'path.js',
+  'path-parse.js',
   'string-decoder.js',
   'zlib.js',
   'domain.js',