Protocol filter: Support home path mapped to UNC share

app/protocol_filter.ts

@@ -29,7 +29,13 @@ export function _urlToPath(
   options?: { isWindows: boolean }
 ): string {
   const decoded = decodeURIComponent(targetUrl);
-  const withoutScheme = decoded.slice(options?.isWindows ? 8 : 7);
+
+  // We generally expect URLs to start with file:// or file:/// here, but for users with
+  //   their home directory redirected to a UNC share, it will start with //.
+  const withoutScheme = decoded.startsWith('//')
+    ? decoded
+    : decoded.slice(options?.isWindows ? 8 : 7);
+
   const withoutQuerystring = _eliminateAllAfterCharacter(withoutScheme, '?');
   const withoutHash = _eliminateAllAfterCharacter(withoutQuerystring, '#');
 

test/app/protocol_filter_test.js

@@ -67,8 +67,24 @@ describe('Protocol Filter', () => {
       expect(actual).to.equal(expected);
     });
 
-    // this seems to be the only way to get a relative path through Electron
-    it('handles SMB share path', () => {
+    it('handles UNC path', () => {
+      const path = '//share/path';
+      const expected = '//share/path';
+
+      const actual = _urlToPath(path);
+      expect(actual).to.equal(expected);
+    });
+
+    it('handles UNC path on windows', () => {
+      const path = '//share/path';
+      const expected = '//share/path';
+      const isWindows = true;
+
+      const actual = _urlToPath(path, { isWindows });
+      expect(actual).to.equal(expected);
+    });
+
+    it('handles simple relative path', () => {
       const path = 'file://relative/path';
       const expected = 'relative/path';
 
@@ -76,7 +92,7 @@ describe('Protocol Filter', () => {
       expect(actual).to.equal(expected);
     });
 
-    it('handles SMB share path on windows', () => {
+    it('handles simple relative path', () => {
       const path = 'file://relative/path';
       const expected = 'elative/path';
       const isWindows = true;