feat(std/path): Add toFileUrl() (#7971)

std/path/mod.ts

@@ -24,6 +24,7 @@ export const {
   relative,
   resolve,
   sep,
+  toFileUrl,
   toNamespacedPath,
 } = path;
 

std/path/posix.ts

@@ -440,3 +440,16 @@ export function fromFileUrl(url: string | URL): string {
     url.pathname.replace(/%(?![0-9A-Fa-f]{2})/g, "%25"),
   );
 }
+
+/** Converts a path string to a file URL.
+ *
+ *      toFileUrl("/home/foo"); // new URL("file:///home/foo")
+ */
+export function toFileUrl(path: string): URL {
+  if (!isAbsolute(path)) {
+    throw new TypeError("Must be an absolute path.");
+  }
+  const url = new URL("file:///");
+  url.pathname = path.replace(/%/g, "%25").replace(/\\/g, "%5C");
+  return url;
+}

std/path/to_file_url_test.ts

@@ -0,0 +1,49 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { posix, win32 } from "./mod.ts";
+import { assertEquals, assertThrows } from "../testing/asserts.ts";
+
+Deno.test("[path] toFileUrl", function () {
+  assertEquals(posix.toFileUrl("/home/foo").href, "file:///home/foo");
+  assertEquals(posix.toFileUrl("/home/ ").href, "file:///home/%20");
+  assertEquals(posix.toFileUrl("/home/%20").href, "file:///home/%2520");
+  assertEquals(posix.toFileUrl("/home\\foo").href, "file:///home%5Cfoo");
+  assertThrows(
+    () => posix.toFileUrl("foo").href,
+    TypeError,
+    "Must be an absolute path.",
+  );
+  assertThrows(
+    () => posix.toFileUrl("C:/"),
+    TypeError,
+    "Must be an absolute path.",
+  );
+  assertEquals(
+    posix.toFileUrl("//localhost/home/foo").href,
+    "file:////localhost/home/foo",
+  );
+  assertEquals(posix.toFileUrl("//localhost/").href, "file:////localhost/");
+  assertEquals(posix.toFileUrl("//:/home/foo").href, "file:////:/home/foo");
+});
+
+Deno.test("[path] toFileUrl (win32)", function () {
+  assertEquals(win32.toFileUrl("/home/foo").href, "file:///home/foo");
+  assertEquals(win32.toFileUrl("/home/ ").href, "file:///home/%20");
+  assertEquals(win32.toFileUrl("/home/%20").href, "file:///home/%2520");
+  assertEquals(win32.toFileUrl("/home\\foo").href, "file:///home/foo");
+  assertThrows(
+    () => win32.toFileUrl("foo").href,
+    TypeError,
+    "Must be an absolute path.",
+  );
+  assertEquals(win32.toFileUrl("C:/").href, "file:///C:/");
+  assertEquals(
+    win32.toFileUrl("//localhost/home/foo").href,
+    "file://localhost/home/foo",
+  );
+  assertEquals(win32.toFileUrl("//localhost/").href, "file:////localhost/");
+  assertThrows(
+    () => win32.toFileUrl("//:/home/foo").href,
+    TypeError,
+    "Invalid hostname.",
+  );
+});

std/path/win32.ts

@@ -917,11 +917,8 @@ export function fromFileUrl(url: string | URL): string {
     throw new TypeError("Must be a file URL.");
   }
   let path = decodeURIComponent(
-    url.pathname
+    url.pathname.replace(/\//g, "\\").replace(/%(?![0-9A-Fa-f]{2})/g, "%25"),
-      .replace(/^\/*([A-Za-z]:)(\/|$)/, "$1/")
+  ).replace(/^\\*([A-Za-z]:)(\\|$)/, "$1\\");
-      .replace(/\//g, "\\")
-      .replace(/%(?![0-9A-Fa-f]{2})/g, "%25"),
-  );
   if (url.hostname != "") {
     // Note: The `URL` implementation guarantees that the drive letter and
     // hostname are mutually exclusive. Otherwise it would not have been valid
@@ -930,3 +927,27 @@ export function fromFileUrl(url: string | URL): string {
   }
   return path;
 }
+
+/** Converts a path string to a file URL.
+ *
+ *      toFileUrl("\\home\\foo"); // new URL("file:///home/foo")
+ *      toFileUrl("C:\\Users\\foo"); // new URL("file:///C:/Users/foo")
+ *      toFileUrl("\\\\localhost\\home\\foo"); // new URL("file://localhost/home/foo")
+ */
+export function toFileUrl(path: string): URL {
+  if (!isAbsolute(path)) {
+    throw new TypeError("Must be an absolute path.");
+  }
+  const [, hostname, pathname] = path.match(
+    /^(?:[/\\]{2}([^/\\]+)(?=[/\\][^/\\]))?(.*)/,
+  )!;
+  const url = new URL("file:///");
+  url.pathname = pathname.replace(/%/g, "%25");
+  if (hostname != null) {
+    url.hostname = hostname;
+    if (!url.hostname) {
+      throw new TypeError("Invalid hostname.");
+    }
+  }
+  return url;
+}