File Handling: Fails from most apps due to read-only permission

[marto55555]

Describe the bug
When opening a file from most apps, into my TWA, it fails with the following error message: Failed to open a file - no read / write permissions: .... From my testing, it seems to happen because most apps send the files as read-only, instead of read and write.

To Reproduce
Steps to reproduce the behavior:

1. Install a demo TWA that registers a file handler, for any file format of your choosing
2. Open "Files by Google", tap on the 3 dots on a file (in the same file format as step 1) > Open with > demo TWA
3. The TWA launches, but without receiving the file
4. See error in Logcat: Failed to open a file - no read / write permissions: ...

Expected behavior
The file should be received, even if it's read-only.

For example, Chrome's File Handling API on Windows allows opening read-only files too.

How Chrome seems to behave with read-only files on Windows

In JS, on the launchParams's FileSystemFileHandle I can call getFile() to read the file without any issues.

However, calling FileSystemFileHandle.createWritable() throws an error: NoModificationAllowedError: Failed to execute 'createWritable' on 'FileSystemFileHandle': Cannot write to a read-only file.

Code Snippets
It seems to be caused by this check:

android-browser-helper/androidbrowserhelper/src/main/java/com/google/androidbrowserhelper/trusted/LauncherActivity.java

Lines 318 to 323 in ba8eb4d

	int granted = checkCallingOrSelfUriPermission(uri,
	Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
	if (granted != PackageManager.PERMISSION_GRANTED) {
	Log.d(TAG, "Failed to open a file - no read / write permissions: " + uri);
	return;
	}

@orbital17 Could you please change it, so that it only checks for Intent.FLAG_GRANT_READ_URI_PERMISSION?

Additional context
For comparison, when using the classic built-in Files app (com.google.android.documentsui) to do Open with > demo TWA, the file is received successfully, because it's sent with read and write permission.

[ukaratkevich]

Hi @SelyvonSerhii, can you take a look too since you worked on this?

[orbital17]

@marto55555 thank you for bringing this up. I'm aware of this issue and working on it.
Unfortunately, it's not possible to fix it immediately, as it also requires androidx.browser changes. I already merged the required changes there, now we need to wait for its next release and I'll be able to fix it here.