[react-transform] Prepend useSignals call if function isn't clearly…

… a component (#458)

It's possible to use the `@trackSignals` comment manually opt-in to the react signals transform on a function that isn't obviously a Component or hook. Before, we would always wrap those functions in a `try/finally` clause. However, this could break signal tracking if the function was actually used as a hook.

For example:
```js
/** @trackSignals */
function badHookName() {
  try {
     // When this hook runs it will close any open effect. Specifically,
     // the effect in Component. This means, upon exiting this hook,
     // all effects will be closed and any signals accesed in "... other stuff ..."
     // in Component will be missed.
     const e = useSignals();
     ...
   } finally {
     e.f() // Finish this hook's effect
   }
}

function Component() {
  try {
    const e = useSignals();
    badHookName();
    // .. other stuff ...
  } finally {
    e.f(); // Finish this hook's effect.
  }
|
```

We fix the bug described in the comment above by just prepending `useSignals()`. This method of tracking signals in React relies on a microtick to close the effect meaning any signals accessed in "... other stuff ..." will be captured by this effect.

More improvements to this scenario will come in a follow up PR.

This PR also adds more tests for transforming hooks in general.

.changeset/little-donuts-notice.md

@@ -0,0 +1,5 @@
+---
+"@preact/signals-react-transform": minor
+---
+
+Only prepend useSignals call if we can't determine whether a function is a component or hook

packages/react-transform/src/index.ts

@@ -348,8 +348,12 @@ function transformFunction(
 		// component. The try/finally in the component's body will stop tracking
 		// signals for us instead.
 		newFunction = prependUseSignals(t, path, state);
-	} else {
+	} else if (isComponentName(functionName)) {
 		newFunction = wrapInTryFinally(t, path, state);
+	} else {
+		// Since we can't determine if this function is a component/hook or not,
+		// we'll just prepend the useSignals call so it will work as either
+		newFunction = prependUseSignals(t, path, state);
 	}
 
 	// Using replaceWith keeps the existing leading comments already so