How to "fetch" local files manifest v3?

[Rory]

Hey guys,

I'm trying to migrate an extension from manifest V2 to V3 and I've encountered an issue. In my extension I am loading a local file by listing the filename in the "web_accessible_resources" section of the manifest, then "fetch"-ing that resource after getting it's URL with "chrome.runtime.getURL". 

If we pretend the file is called "data.txt" then the problematic section of code looks something like this:

data = fetch(chrome.runtime.getURL("data.txt")).then(response => response.text())

However, I am no longer able to use "fetch" to retrieve my local file (I think because "fetch" has been limited to prevent loading remote-code). Any ideas how I can circumvent this issue in manifest V3?

Thanks,

Rory

[Jackie Han]

Fetching local files works for me in MV3. I don't have the problem you said.

Jackie Han

Rory <rorygar...@gmail.com> 于2021年3月7日周日 下午1:23写道：

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[Deco]

Have you tried using getURL? It shouldn't work in this scenario as the local file becomes an external resource, which is blocked in Manifest V3.

Thanks,

Deco

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[wOxxOm]

MV3 uses a new format for web_accessible_resources so maybe yours is incorrect?

See https://developer.chrome.com/docs/extensions/mv3/intro/mv3-migration/#web-accessible-resources

"web_accessible_resources": [{
  "resources": ["data.txt"],
  "matches": []
}]

  

[guest271314]

When you chain catch(console.error) to fetch() what is logged at console?

I have not tried in some time, though chrome: protocol might not be supported by Fetch Standard. 

You can get the file using File System Access API (Native File System).

[guest271314]

console.log(await (await (await showOpenFilePicker())[0].getFile()).text())

[wOxxOm]

> chrome: protocol might not be supported by Fetch Standard. 

It's not chrome, it's chrome-extension:// and it's intentionally allowed for content scripts, this is how web_accessible_resources is implemented.

> You can get the file using File System Access API (Native File System).

> console.log(await (await (await showOpenFilePicker())[0].getFile()).text())

Don't be confused by the OP's usage of the word "local". Their code clearly indicated the subject is a file from an extension package declared via web_accessible_resources.

[Jackie Han]

Deco,

Yes, I tested it in MV3. I use fetch api from an extension page to fetch another file in this extension. See below screenshot:

If you use it in content script, see wOxxOm's answer, it has a new format and restriction for "web_accessible_resources".

Deco <decklin...@gmail.com> 于2021年3月7日周日 下午8:11写道：

[Deco]

Ah thanks, it was my error of judgement from reading the OP's post, I assumed it was an externally loaded asset as I missed the use of web_accessible_resources.

Regards,

Deco

[Rory]

Thanks everyone.

It's an html file not a txt file by the way, not sure if that matters, I just used text in the example. Maybe this is why.

Everything I've tried in here has not worked - it keeps saying:

Denying load of chrome-extension://hgipopnedpcknmapfakdedlnjjkmpnao/widget.html. Resources must be listed in the web_accessible_resources manifest key in order to be loaded by pages outside the extension.

I'm using this line in the content script:

await fetch(chrome.runtime.getURL("widget.html"))

and in the manifest it's declared to MV3 specifications (screenshot attached).

I must be missing something small. Is it because it's html? This hasn't been a problem up until now.

Thank you for your assistance on this.

[Rory]

Worth noting - it IS in the same folder as the manifest. So, that file path in the manifest should be fine.

[wOxxOm]

Looks like "matches" in web_accessible_resources is actually required now so it should look like "matches": ["<all_urls>"] in case you expose it on all URLs.

[Rory]

Thanks w0xx0m, this fixed it.

[Ravish Desai]

Hello world, i want to develop an extension to extract the information from a page and display it into side bar in chrome extension, can you tell from where shall I start?