[Feature]: Allow relative URLs in trace-viewer trace param

[vitalets]

🚀 Feature Request

I propose to add support of relative URLs to the trace-viewer trace parameter.

Example

Currently, trace-viewer URLs look like this:

http://localhost:9323/trace/index.html?trace=http://localhost:9323/data/9ed7c5d3b9be501f8179e4cacebced0ccbbcac7b.zip

I'd like to request a support of relative URLs in the trace param:

http://localhost:9323/trace/index.html?trace=/data/9ed7c5d3b9be501f8179e4cacebced0ccbbcac7b.zip

If trace is relative, trace-viewer resolves it from it's hostname (localhost:9323 in the example above).
Then all other checks run as usual, e.g. checking for file:// scheme.

I've checked the trace-viewer sources, looks like it could be achieved by a tiny change next to getting trace URLs:

// resolve relative trace urls
for (let i = 0; i < newTraceURLs.length; i++) {
  const url = newTraceURLs[i];
  if (url.startsWith('/')) {
    newTraceURLs[i] = new URL(url, window.location.toString()).href;
  }
}

If approved, I'm ready to submit a PR.

Motivation

I use trace-viewer URLs in a custom HTML reporter. The report file is served via a local HTTP server, started by the user on a random port. Since the port is unknown beforehand, I cannot generate reliable trace-viewer URLs.

This small addition will simplify integration with third-party tools and help the Playwright ecosystem evolve.

[agg23]

This sounds like a good improvement. PRs are welcome.

[vitalets]

I tried implementing it and discovered that the trace-viewer accepts paths for the trace parameter. For example, a relative path:

http://localhost:9323/trace/index.html?trace=./playwright-report/data/bcfdcb3222cbd1de760f9ecd1329ad7739e6037e.zip

Or an absolute path:

http://localhost:9323/trace/index.html?trace=/Users/vitalets/projects/my-project/playwright-report/data/9ed7c5d3b9be501f8179e4cacebced0ccbbcac7b.zip

To support relative URLs in the trace parameter, we need to address the ambiguity. When I provide trace=/path/to/trace.zip, should the trace-viewer pass it through to look up on the filesystem, or should it prepend its own hostname?

I could introduce a query parameter, isUrl=true, to indicate that the provided path is expected to be a URL.
What do you think?

[agg23]

Thinking about this further, why do you not know the current port? You know your current hostname and port; does that not match the Trace Viewer server?

[vitalets]

I'm serving trace-viewer from a local static webserver, started as npx http-server. It picks free port randomly.

If I start it with the hardcoded port (e.g. npx http-server --port 1234) then I also need to configure my custom reporter to generate trace-viewer links with that port, like trace/index.html?trace=http://localhost:1234/data/.... That is less convenient and actually duplicates the config.

I think, it would be useful to make trace-viewer "servable" from a regular static server.
I assume it will also simplify a couple of places in the Playwright itself, where currently http server aliases trace/file?path=xxx to serve the xxx path statically. I found it here and here.