[PHP.wasm] Stream stdout and stderr data to the API consumer instead of buffering it

[adamziel]

PHP.wasm redirects the output streams to files, e.g. /internal/stdout. This is caused by an Emscripten limitation – a null byte in the stdout stream is treated as the end of that stream. Let's find a way for PHP to stream the output data piece by piece – this would unlock faster rendering, streaming data between two Playgrounds, and stream-exporting entire sites as ZIP files without running out of memory.

[obenland]

I'm exploring to run wp plugin check via run-blueprint to let developers validate plugins before submitting to the Plugin Directory.

The wp-cli blueprint step runs successfully, but its output is lost. There's a workaround with wp eval + ob_start() + file_put_contents() to a mounted output directory, but it adds quite a bit of complexity.

If run-blueprint printed wp-cli step stdout to the terminal, the entire flow would be:

npx @wp-playground/cli run-blueprint --auto-mount=./my-plugin --blueprint=blueprint.json

{
  "steps": [
    {"step": "installPlugin", "pluginData": {"resource": "wordpress.org/plugins", "slug": "plugin-check"}},
    {"step": "wp-cli", "command": "wp plugin activate plugin-check"},
    {"step": "wp-cli", "command": "wp plugin check my-plugin --categories=plugin_repo --format=json"}
  ]
}

Even a targeted fix, run-blueprint reads back /internal/stdout after each step and pipes it to the terminal, would unblock this without needing full streaming.

As an aside, if --blueprint also accepted a JSON string instead of only a file path, this could be a true one-liner without any temp files 🤞

[bgrgicak]

The wp-cli blueprint step runs successfully, but its output is lost. There's a workaround with wp eval + ob_start() + file_put_contents() to a mounted output directory, but it adds quite a bit of complexity.

@obenland and I discussed this today, and I pointed out that Blueprints are designed to set up sites rather than produce outputs. As an alternative, we explored Konstantin's approach of storing the output in files and creating a script that uses runCli to get the check output.

[adamziel]

There's a new php command for Playground CLI that just runs a PHP script, would that help @obenland?

#2641

I get that Blueprints would still be useful for this if they provided the output. Maybe it wouldn't be that difficult to add support for that? It should help with debugging Blueprints, too. Maybe we could print the output in a verbose mode or so? If you'd be game for starting a PR for this (and another one for providing an inline Blueprint, since that makes sense as well), I don't see any reason not to have that.

Also, this isn't the right issue, in fact this one is already solved as we do have output streams so I'll close it.

[obenland]

Yes! I'm now down to a small blueprint file and one command, excellent.

{
	"steps": [
		{"step": "installPlugin", "pluginData": {"resource": "wordpress.org/plugins", "slug": "plugin-check"}},
		{"step": "wp-cli", "command": "wp plugin activate plugin-check"}
	]
}

npx @wp-playground/cli php \
	--blueprint=blueprint.json \
	--mount=./my-plugin:/wordpress/wp-content/plugins/my-plugin \
	--quiet \
	-- /tmp/wp-cli.phar plugin check my-plugin \
	--categories=plugin_repo --format=json