On my DNA-23526 bug-report I got this answer:

Could you try using following paths
/etc/chromium/native-messaging-hosts
or:
<OPERA_PROFILE_DIR>/NativeMessagingHosts
Profile path will be displayed on opera:about page.`

Opera:about doesn't show anything about a google-chrome path, but mentioned path worked at that moment. Please don't blame me for filing more bug reports when it stopped working. The path really changed between versions, without documentation or rationale.

And it feels wrong and risky:
If Google-Chrome isn't installed, the google-chrome path is a path any program can create/write to.

And when you have Chrome installed and decide to drop it because you prefer Opera, and remove Chrome and all of it's settings, suddenly Opera fails. Doesn't make sense to me.

/Library/Google/Chrome/NativeMessagingHosts/...

That should be corrected to:

~/Library/Application Support/Google/Chrome/NativeMessagingHosts/...

Native messaging is supposed to work as mentioned in the documentation. I've made some minor fixes in the docs, but the point remains that right now Opera looks for the chrome directory. We're re-evaluating again on whether to change this approach or not, but so far, as you have also experienced, it works as is.

So I've sent an update to DNAWIZ-3797 (My previous comment had wrong DNA number.)

@janghour: Sorry I didn't quite understand your first posts. As I said earlier, my extension did not launch its native messaging tool when I installed a Native Messaging manifest file in the /Library/Google/Chrome… system directory as specified in the documentation, nor when I installed it in any reasonable Opera directory. However, just now I added the ID of the extension installed in Opera to the allowed_origins in Native Messaging manifest file I have installed for Chrome,

~/Library/Application Support/Google/Chrome/NativeMessagingHosts

and now, amazingly, my native messaging tool launches as expected when Opera loads my extension! My plans were to use the same native messaging tool for both Chrome and Opera, anyhow.

So, @kszularz, although it looks ridiculous, this might work, as is. I shall update my bug at DNAWIZ-3730 after doing some more testing.

• DNA-23526
• DNA-43909
• DNAWIZ-3730

Big thanks for such a detailed investigation on this topic.

I'm really sorry to hear this bug as well as errors in the documentation prevent you from writing great extensions for Opera.

Now the big report is going to be reviewed by our QA team.

What happens when you install your extensions, I can get them working using the Google Chrome path for the manifest.

DNAWIZ-3797.

The remainder of this post is the text of my bug report.

Summary

I have developed browser extensions for many years, including one for Google Chrome, which uses their Native Messaging API. Even though Vivaldi does not provide any documentation, it works in Vivaldi the same as it does in Chrome, with obvious changes. I was able to install my extension and get it working in Vivaldi in less than an hour. But I cannot get it to work in Opera, and after trying every reasonable variation on the ambiguities in the documentation, I have concluded that the Native Messaging API does not work in Opera when running in mac OS (OS X). I am using Opera version 38.

Details

When my extension runs in Opera, the line of JavaScript code which is supposed to open a port,

port = chrome.runtime.connectNative(hostName);

executes successfully (without raising) in a try{} block, and returns what appears to be a port object, but its properties are rather empty, and my native binary does not launch, as it does when my extension runs in Google Chrome or Vivaldi.

In looking at that documentation, I find it strange that my I am told to install my Native Messaging manifest file here:

• /Library/Google/Chrome/NativeMessagingHosts/com.mycompany.myapplication.json

First of all, the Google/Chrome subdirectory is owned by, you know, the wrong browser company. Second, because this path does not begin with a tilde (~) it is, eeeek, in a system-admin level directory. Because of this, I had to enter my administrator password twice in order to create the folder and put it there. Google Chrome gives you the option to put it in the user's directory instead, which I do for my Chrome extension.

I also tried putting my Native Messaging manifest file in other reasonable locations:

• ~/Library/Google/Chrome/NativeMessagingHosts/
• ~/Library/Application Support/com.operasoftware.Opera/NativeMessagingHosts/
• ~/Library/Application Support/Opera/NativeMessagingHosts/

but none of these worked either.

In addition to the Google/Chrome path mentioned above, there are other indications that this documentation was never thoroughly reviewed and tested, for example,

Chrome starts the host in a separate process…

Obviously, this should have been changed to:

Opera starts the host in a separate process…

To resolve this issue, Opera staff should please review the documentation and make corrections as necessary so that they can make a simple example extension which works, and post a link to it in the documentation. Maybe I'm making some silly mistake, but, you know for something like this, with multiple moving parts, a working example is essential.

Thank you for reading.

Jerry Krinock

~/.config/google-chrome/NativeMessagingHosts

Now I know why the example works, I had it also installed in Google Chrome, not my own extensions. When I place the manifest in above Google Chrome location the extension starts working.

Will file another bug report, pfff.

To debug

• start Opera from terminal, it will give you some errors in terminal.
• Try the official example.
  Strangely that one works in Opera, while my own do not work in Opera, but they do work in Chromium.

Path to manifest (I use it in opera-developer).

• On Linux: ~/.config/opera-developer/NativeMessagingHosts/com.my_company.my_application.json
• On OSX (I guess): ~/Library/Application Support/Opera/NativeMessagingHosts/com.my_company.my_application.json
• for chromium: ~/.config/chromium/NativeMessagingHosts/com.my_company.my_application.json

Annoyingly, there is no error message, when you have set the extension ID wrong

"allowed_origins": [ "chrome-extension://xxx/" ]

~/Library/Application Support/com.operasoftware.OperaDeveloper/NativeMessagingHosts

But still my messaging tool does not launch.

I've also looked through the Opera Add-Ons for another extension which I thought might be using Native Messaging but could not find any. I imagine that they would need to be associated with a native app that would install the manifest and messaging tool, like my extension.

Has anyone ever used Native Messaging in an Opera Extension? I wonder if this feature has ever been tested?

Thank you!