Module fs

High level browser to file system integration library.

This library integrates the File, FileEntry and FileSystemAccess API to provide different levels of integration with file system in web apps.

Basically, user can select a directory as a mount point, and browser can access read and sometimes write in the directory.

Support

Use fsGetSupportStatus() to inspect which implementation will be used.

import { fsGetSupportStatus } from "@pistonite/pure/fs";

const { implementation, isSecureContext } = fsGetSupportStatus();
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implementation can be 3 values:

1. FileSystemAccess: This is used for Google Chrome and Edge, and possibly other browsers, under secure context.
2. FileEntry: This is used for Firefox when the FS is mounted through a drag-and-drop interface.
3. File: This is used for Firefox when the FS is mounted by a directory picker dialog

The implementation is also chosen in this order and the first supported one is selected. If you are on Chrome/Edge and FileSystemAccess is not used, you can use isSecureContext to narrow down the reason.

If you are wondering why Safari is not mentioned, it's because Apple made it so I have to buy a Mac to test, which I didn't.

After you get an instance of FsFileSystem, you can use capabilities to inspect what is and is not supported.

See FsCapabilities for more info. This is the support matrix:

Implementation	write?	live?
FileSystemAccess	Yes*	Yes
FileEntry	No	Yes
File	No	No

* = Need to request permission from user.

Usage

First you need to get an instance of FsFileSystem. You can:

1. Call fsOpenRead() or fsOpenReadWrite() to show a directory picker,
2. Call fsOpenReadFrom or fsOpenReadWriteFrom() and pass in a DataTransferItem from a drag-and-drop interface.

NOTE: fsOpenReadWrite does not guarantee the implementation supports writing. You should check with capabilities afterward.

This is an example drop zone implementation in TypeScript

import { fsOpenReadWriteFrom } from "@pistonite/pure/fs";

const div = document.createElement("div");

div.addEventListener("dragover", (e) => {
    if (e.dataTransfer) {
        // setting this will allow dropping
        e.dataTransfer.dropEffect = "link";
    }
});

div.addEventListener("drop", async (e) => {
    const item = e.dataTransfer?.items[0];
    if (!item) {
        console.error("no item");
        return;
    }

    const result = await fsOpenReadWriteFrom(item);
    if (result.err) {
        console.error(result.err);
        return;
    }

    const fs = result.val;
    const { write, live } = fs.capabilities;
    // check capabilities and use fs
    // ...
});
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Retry open

You can pass in a retry handler and return true to retry, when opening fails. The handler is async so you can ask user.

import { FsError, FsResult } from "@pistonite/pure/fs";

async function shouldRetry(error: FsError, attempt: number): Promise<FsResult<boolean>> {
    if (attempt < 10 && error === FsError.PermissionDenied) {
        alert("you must give permission to use this feature!");
        return { val: true };
    }
    return { val: false };
}

const result = await fsOpenReadWrite(shouldRetry);
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