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[recovery] fix: make image placeholder cache I/O best-effort on read-only runtime FS #18793

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[recovery] fix: make image placeholder cache I/O best-effort on read-only runtime FS #18793

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21 changes: 16 additions & 5 deletions src/lib/md/rehypeImg.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -85,9 +85,19 @@ const setImagePlaceholders = async (
.replaceAll("/", "-")
.slice(1)

// The on-disk placeholder cache is a build-time optimization. When MDX is
// compiled on-demand in the serverless runtime the filesystem is read-only
// (and this dir isn't bundled), so treat cache I/O as best-effort and fall
// back to generating placeholders in memory.
let canWriteCache = true

// Make directory for current page if none exists
if (!fs.existsSync(PLACEHOLDER_IMAGE_DIR))
fs.mkdirSync(PLACEHOLDER_IMAGE_DIR, { recursive: true })
try {
if (!fs.existsSync(PLACEHOLDER_IMAGE_DIR))
fs.mkdirSync(PLACEHOLDER_IMAGE_DIR, { recursive: true })
} catch {
canWriteCache = false
}

const DATA_PATH = path.join(PLACEHOLDER_IMAGE_DIR, FILENAME)
const existsCache = fs.existsSync(DATA_PATH)
Expand Down Expand Up @@ -133,15 +143,16 @@ const setImagePlaceholders = async (

// If cache is still empty, delete JSON file and return
if (Object.keys(placeholdersCached).length === 0) {
fs.rmSync(DATA_PATH, { recursive: true, force: true })
if (canWriteCache) fs.rmSync(DATA_PATH, { recursive: true, force: true })
return
}

// If cached value has not changed, return without writing to file system
if (!isChanged) return

// Write results to cache file
fs.writeFileSync(DATA_PATH, JSON.stringify(placeholdersCached, null, 2))
// Write results to cache file (skipped when the FS is read-only at runtime)
if (canWriteCache)
fs.writeFileSync(DATA_PATH, JSON.stringify(placeholdersCached, null, 2))
}

/**
Expand Down
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