6 files changed, 74 insertions, 11 deletions
diff --git a/cli/js/lib.deno.shared_globals.d.ts b/cli/js/lib.deno.shared_globals.d.ts
index ef870d2aa..635fa391e 100644
--- a/cli/js/lib.deno.shared_globals.d.ts
+++ b/cli/js/lib.deno.shared_globals.d.ts
@@ -1092,7 +1092,7 @@ interface URL {
 
 declare const URL: {
   prototype: URL;
-  new (url: string, base?: string | URL): URL;
+  new (url: string | URL, base?: string | URL): URL;
   createObjectURL(object: any): string;
   revokeObjectURL(url: string): void;
 };
diff --git a/cli/js/web/url.ts b/cli/js/web/url.ts
index 6a8dc6627..3d513a010 100644
--- a/cli/js/web/url.ts
+++ b/cli/js/web/url.ts
@@ -356,7 +356,7 @@ export class URLImpl implements URL {
     return this.#searchParams;
   }
 
-  constructor(url: string, base?: string | URL) {
+  constructor(url: string | URL, base?: string | URL) {
     let baseParts: URLParts | undefined;
     if (base) {
       baseParts = typeof base === "string" ? parse(base) : parts.get(base);
@@ -365,7 +365,7 @@ export class URLImpl implements URL {
       }
     }
 
-    const urlParts = parse(url);
+    const urlParts = typeof url === "string" ? parse(url) : parts.get(url);
     if (!urlParts) {
       throw new TypeError("Invalid URL.");
     }
diff --git a/std/path/from_file_url_test.ts b/std/path/from_file_url_test.ts
new file mode 100644
index 000000000..79389b91b
--- /dev/null
+++ b/std/path/from_file_url_test.ts
@@ -0,0 +1,37 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import * as path from "./mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+
+Deno.test("[path] fromFileUrl", function () {
+  assertEquals(
+    path.posix.fromFileUrl(new URL("file:///home/foo")),
+    "/home/foo"
+  );
+  assertEquals(path.posix.fromFileUrl("file:///home/foo"), "/home/foo");
+  assertEquals(path.posix.fromFileUrl("https://example.com/foo"), "/foo");
+  assertEquals(path.posix.fromFileUrl("file:///"), "/");
+});
+
+Deno.test("[path] fromFileUrl (win32)", function () {
+  assertEquals(
+    path.win32.fromFileUrl(new URL("file:///home/foo")),
+    "\\home\\foo"
+  );
+  assertEquals(path.win32.fromFileUrl("file:///home/foo"), "\\home\\foo");
+  assertEquals(path.win32.fromFileUrl("https://example.com/foo"), "\\foo");
+  assertEquals(path.win32.fromFileUrl("file:///"), "\\");
+  // FIXME(nayeemrmn): Support UNC paths. Needs support in the underlying URL
+  // built-in like Chrome has.
+  // assertEquals(path.win32.fromFileUrl("file:////"), "\\");
+  // assertEquals(path.win32.fromFileUrl("file:////server"), "\\");
+  // assertEquals(path.win32.fromFileUrl("file:////server/file"), "\\file");
+  assertEquals(path.win32.fromFileUrl("file:///c"), "\\c");
+  assertEquals(path.win32.fromFileUrl("file:///c:"), "\\c:");
+  assertEquals(path.win32.fromFileUrl("file:///c:/"), "c:\\");
+  assertEquals(path.win32.fromFileUrl("file:///C:/"), "C:\\");
+  assertEquals(path.win32.fromFileUrl("file:///C:/Users/"), "C:\\Users\\");
+  assertEquals(
+    path.win32.fromFileUrl("file:///C:cwd/another"),
+    "\\C:cwd\\another"
+  );
+});
diff --git a/std/path/mod.ts b/std/path/mod.ts
index 402adcf00..104e0b616 100644
--- a/std/path/mod.ts
+++ b/std/path/mod.ts
@@ -11,19 +11,20 @@ const path = isWindows ? _win32 : _posix;
 export const win32 = _win32;
 export const posix = _posix;
 export const {
-  resolve,
-  normalize,
-  isAbsolute,
-  join,
-  relative,
-  toNamespacedPath,
-  dirname,
   basename,
+  delimiter,
+  dirname,
   extname,
   format,
+  fromFileUrl,
+  isAbsolute,
+  join,
+  normalize,
   parse,
+  relative,
+  resolve,
   sep,
-  delimiter,
+  toNamespacedPath,
 } = path;
 
 export { common } from "./common.ts";
diff --git a/std/path/posix.ts b/std/path/posix.ts
index ba4cf7499..156aba796 100644
--- a/std/path/posix.ts
+++ b/std/path/posix.ts
@@ -421,3 +421,14 @@ export function parse(path: string): ParsedPath {
 
   return ret;
 }
+
+/** Converts a file URL to a path string.
+ *
+ *      fromFileUrl("file:///home/foo"); // "/home/foo"
+ *
+ * Note that non-file URLs are treated as file URLs and irrelevant components
+ * are ignored.
+ */
+export function fromFileUrl(url: string | URL): string {
+  return new URL(url).pathname;
+}
diff --git a/std/path/win32.ts b/std/path/win32.ts
index 9bba66e2b..2c262b1b6 100644
--- a/std/path/win32.ts
+++ b/std/path/win32.ts
@@ -898,3 +898,17 @@ export function parse(path: string): ParsedPath {
 
   return ret;
 }
+
+/** Converts a file URL to a path string.
+ *
+ *      fromFileUrl("file:///C:/Users/foo"); // "C:\\Users\\foo"
+ *      fromFileUrl("file:///home/foo"); // "\\home\\foo"
+ *
+ * Note that non-file URLs are treated as file URLs and irrelevant components
+ * are ignored.
+ */
+export function fromFileUrl(url: string | URL): string {
+  return new URL(url).pathname
+    .replace(/^\/(?=[A-Za-z]:\/)/, "")
+    .replace(/\//g, "\\");
+}