fix: extract shared logic for server island loading into a function and only include it once

[ascorbic]

Changes

Currently, each server island includes a script to load its own content. That includes quite a bit of logic that could be shared between islands. This PR extracts that into a function that can be reused by each island, and includes it only once. This runtime script is defined as a classic, non-module script so that we can guarantee that it has always executed before any of the module scripts runs.

Testing

Added and updated tests

Docs

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Latest commit: c297c5c

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commit: 9d93448

[codspeed-hq]

CodSpeed Performance Report

Merging #13576 will not alter performance

_{Comparing si-dedupe (c297c5c) with main (a0774b3)}

Summary

✅ 6 untouched benchmarks

[matthewp]

I would suggest using the render instruction for this, this is how we do the same thing to only render the hydration scripts once. The advantage is that you know for sure that the script is always rendered before the usage. I know that in this case we're using module scripts, but if you ever want to change that in the future you'd want to use render instructions instead.

Here's an example of the usage in hydration scripts.

• Where we need to use the hydration script:

  astro/packages/astro/src/runtime/server/render/component.ts

  Line 384 in 9ec242a

  destination.write(createRenderInstruction({ type: 'directive', hydration }));

• Here's where the string is rendered, to ensure its only done once:

  astro/packages/astro/src/runtime/server/render/common.ts

  Line 64 in 9ec242a

  let needsHydrationScript = hydration && determineIfNeedsHydrationScript(result);