Cannot consistently start chromium on macOS

[jezhou]

Is this a feature request or a bug?

Bug

What is the current behavior?

When I run web-ext run --target chromium, it doesn't seem to correctly start the Websocket server, which prevents Chrome + the extension from launching. This also happens when I run npm test in the web-ext project.

Running web-ext test suite

Running web-ext cli with chromium

Curiously, this will sometimes work if I use node v13.2.

I have Chrome installed on my computer. Am I missing a step in the setup?

What is the expected or desired behavior?

Websocket server is successfully started, and Chrome + the extension launches consistently.

Version information (for bug reports)

macOS
10.14.6

Chrome
78.0.3904.108

node --version && npm --version && npx web-ext --version
v10.15.1, v13.2.0
6.11.3
3.2.1

[Rob--W]

wss is set at the start of setupInstance, at

web-ext/src/extension-runners/chromium.js

Line 93 in 7ee3c44

this.wss = new WebSocket.Server({

The error is "Cannot read property 'address' of null", which implies that wss has become null. This only happens when exit() is called -

web-ext/src/extension-runners/chromium.js

Line 301 in 7ee3c44

this.wss = null;

If this error occurs, then exit() has most likely been called, unexpectedly.

[rpl]

Interestingly it seems that we are triggering the same failure in the windows travis worker on an unrelated pull request (#1780): https://travis-ci.org/mozilla/web-ext/jobs/623117080#L682-L688