is there a way to check if the PWA was launched through a file or not? - progressive-web-apps

Question

I'm using the file handle API to give my web app the optional capability to launch through double-clicking files in the file explorer.
Writing the code below, I expected if (!("files" in LaunchParams.prototype)) to check if a file was used to launch the app, but apparently, it checks if the feature is supported. OK, that makes sense.
After that, I thought the setConsumer callback would be called in any launch scenario, and files.length would be zero if the app was launched in other ways (like by typing the URL in the browser). But on those use cases, the callback was not called at all, and my init logic was never executed.
if (!("launchQueue" in window)) return textRecord.open('a welcome text');
if (!("files" in LaunchParams.prototype)) return textRecord.open('a welcome text');
launchQueue.setConsumer((launchParams) => {
if (launchParams.files.length <= 0) return textRecord.open('a welcome text');
const fileHandle = launchParams.files[0];
textRecord.open(fileHandle);
});
I've also followed the Launch Handler API article instructions and enabled the experimental API.
The new code confirms that "targetURL" in LaunchParams.prototype is true, but the setConsumer callback is not executed if the user accesses the web app through a standard browser tab.
function updateIfLaunchedByFile(textRecord) {
if (!("launchQueue" in window)) return;
if (!("files" in LaunchParams.prototype)) return;
console.log({
'"targetURL" in LaunchParams': "targetURL" in LaunchParams.prototype,
});
// this is always undefined
console.log({ "LaunchParams.targetURL": LaunchParams.targetURL });
// setConsumer does not trigger if the app is not launched by file, so it is not a good place to branch what to do in every launch situation
launchQueue.setConsumer((launchParams) => {
// this never run in a normal tab
console.log({ setConsumer: launchParams });
if (launchParams.files.length <= 0) return;
const fileHandle = launchParams.files[0];
textRecord.open(fileHandle);
});
}
This is the result...
Is there a universal way to check if the web app was launched through a file?

Answer 1

Check out the Launch Handler origin trial. It lets you determine the launch behavior exactly and lets your app detect how the launch happened. This API works well together with the File Handling API that you already use. You could, for example, check the LaunchParams.targetURL to see how the app was launched. Your feedback is very welcome.

Answer 2

Since I was not able to guarantee that the setConsumer callback was called in every situation (especially when the app is launched in a regular browser tab), I hacked it through setTimeout:
function wasFileLaunched() {
if (!("launchQueue" in window)) return;
if (!("files" in LaunchParams.prototype)) return;
return new Promise((resolve) => {
let invoked = false;
// setConsumer does not triggers if the app is not launched by file, so it is not a good place to branch what to do in every launch situation
launchQueue.setConsumer((launchParams) => {
invoked = true;
if (launchParams.files.length <= 0) return resolve();
const fileHandle = launchParams.files[0];
resolve(fileHandle);
});
setTimeout(() => {
console.log({ "setTimeout invoked =": invoked });
if (!invoked) resolve();
}, 10);
});
}