Automatically purge cache on version change

[NathanFlurry]

Motivation

OpenGB doesn't manage cache compat between versions. It should auto-purge the cache if the version changes.

[linear]

OGBE-163 Automatically purge cache on version change

[greptile-apps]

To automatically purge the cache on version change, update the loadCache function in src/build_state/cache.ts to reset the cache if the version has changed. Here are the specific steps:

1. Modify the loadCache function to include a version check and reset the cache if the version has changed:

export async function loadCache(project: Project): Promise<Cache> {
  const buildCachePath = genPath(project, CACHE_PATH);

  // Read hashes from file
  let persist: CachePersist;
  if (await exists(buildCachePath)) {
    try {
      const oldCacheAny: any = JSON.parse(
        await Deno.readTextFile(buildCachePath),
      );

      // Validate version
      if (oldCacheAny.version == CACHE_VERSION) {
        persist = oldCacheAny;
      } else {
        persist = createEmptyCachePersist();
        await writeCache(project, { persist, hashDiffs: new Map() }); // Purge cache
      }
    } catch {
      // If parsing fails or the cache isn't readable, reset the cache.
      persist = createEmptyCachePersist();
    }
  } else {
    persist = createEmptyCachePersist();
  }

  return {
    persist,
    hashDiffs: new Map(),
  };
}

This ensures that the cache is automatically purged and reset whenever the CACHE_VERSION changes.

References

/src/build_state/cache.ts

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