Fix race condition when setting up Strada components

[dginsburg]

There is a race condition that has been discussed in #20. The symptom is that messages aren't received in the native adapter from Strada JS components after pulling to refresh.

Racer 1

The JS shim is injected .atDocumentStart

strada-ios/Source/Bridge.swift

Line 147 in d8c1bcf

return WKUserScript(source: source, injectionTime: .atDocumentStart, forMainFrameOnly: true)

ready message is posted to the native adapter

strada-ios/Source/strada.js

Lines 70 to 71 in d8c1bcf

	window.nativeBridge = new NativeBridge()
	window.nativeBridge.postMessage("ready")

It goes through the Swift code and eventually calls register to set the supportedComponents

strada-ios/Source/strada.js

Lines 11 to 19 in d8c1bcf

	register(component) {
	if (Array.isArray(component)) {
	this.supportedComponents = this.supportedComponents.concat(component)
	} else {
	this.supportedComponents.push(component)
	}
	this.notifyBridgeOfSupportedComponentsUpdate()
	}

Racer 2

strada-web dispatches web-bridge: ready
https://github.com/hotwired/strada-web/blob/df1c2b40234286dad55815aaf78b31f8691693e9/src/bridge.js#L18-L20

The native app calls setAdapter upon receiving that event

strada-ios/Source/strada.js

Line 8 in d8c1bcf

document.addEventListener("web-bridge:ready", () => this.webBridge.setAdapter(this))

Once the adapter is set, strada-web is free to send messages. Before it sends a message it calls supportsComponent.

strada-ios/Source/strada.js

Lines 35 to 37 in d8c1bcf

	supportsComponent(component) {
	return this.supportedComponents.includes(component)
	}

Solution

Racer 1 is setting supportedComponents and Racer 2 requires it to already be set. The two racers aren't correlated and either path can get there first.

I think something like this PR is the best way to solve it. It's NativeBridge's responsibility to be fully set up before calling setAdapter.

I'm not a JS dev and used AI ✨ to help me write a Promise. Tell me or just change it if you think there is a better way.

[svara]

It's NativeBridge's responsibility to be fully set up before calling setAdapter.

Agree, and I like the proposed solution.

@jayohms @joemasilotti Could you guys take a look at the code please?

[joemasilotti]

Approved assuming that when this gets merged on top of #32 the tests will pass.