Introduce throwOnFailure option for prerender

[resolritter]

Problem

Due to some unknown issue with lazy, the prerender function was not working as intended for my components. I eventually overcame that problem, but I did not know it was was happening in the first plac until I looked into the generated HTML and noticed it was wrong. In other words, the prerender is failing silently since the error path is not being handled correctly, as I'll explain below.

The problem is related to this line:

wmr/packages/preact-iso/prerender.js

Line 49 in 3c5672e

let html = await render();

The render function was returning undefined because my components could not be rendered correctly. Then we go into the next line:

wmr/packages/preact-iso/prerender.js

Line 50 in 3c5672e

html += `<script type="isodata"></script>`;

Since html was undefined, the generated HTML would become undefined<script type="isodata"></script>, which is not what I want.

Solution

There should be a way of generating an exception in case the components cannot be rendered correctly. For that, this PR introduces the throwOnFailure option which controls what happens in case rendering fails. It defaults to a falsy value for preserving prerender's current behavior, but arguably it should be true.

[changeset-bot]

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Latest commit: d4f8dd9

The changes in this PR will be included in the next version bump.

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Name	Type
preact-iso	Minor

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