What causes "cannot read ${file} when saving inline snapshot" in vitest-dev/vitest?

vitest-dev/vitest · error · Error

cannot read when saving inline snapshot

Error message

cannot read ${file} when saving inline snapshot

What it means

While saving inline snapshots, saveInlineSnapshots reads each affected source file via environment.readSnapshotFile; if that returns null (file missing, unreadable, or the environment cannot read it), the writer cannot compute offsets to insert/replace snapshots and aborts.

Defensive patterns

Strategy: try-catch

Validate before calling

// Pre-check the source file is readable before running inline snapshots
const code = await environment.readSnapshotFile(file)
if (code == null) throw new Error(`source file ${file} is not readable; cannot save inline snapshot`)

Try / catch

try {
  await saveInlineSnapshots(environment, snapshots)
} catch (e) {
  if (e instanceof Error && /cannot read .* when saving inline snapshot/.test(e.message)) {
    // restore/recreate the file, or write snapshots manually
  } else throw e
}

Prevention

Ensure source files exist and are readable for the whole test run
Implement readSnapshotFile to return string contents in custom environments
Avoid moving/deleting test files mid-run

When it happens

Trigger: An inline snapshot assertion whose source file was deleted, moved, or made unreadable between the test run and the save phase; a custom SnapshotEnvironment whose readSnapshotFile returns null; permission error on the source file.

Common situations: File deleted/renamed mid-run; running tests in a read-only or sandboxed FS where the environment cannot read the source; custom environment with a broken readSnapshotFile; race where another process moved the file.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/f86468bc07d99a64. Report an issue: GitHub.

Appendix: source

Thrown at packages/snapshot/src/port/inlineSnapshot.ts:34

  column: number
  // it maybe possible to accurately extract this from `ParsedStack.method`,
  // but for now, we ask higher level assertion to pass it explicitly
  // since this is useful for certain error messages before we extract stack.
  assertionName?: string
}

export async function saveInlineSnapshots(
  environment: SnapshotEnvironment,
  snapshots: Array<InlineSnapshot>,
): Promise<void> {
  const MagicString = (await import('magic-string')).default
  const files = new Set(snapshots.map(i => i.file))
  await Promise.all(
    Array.from(files).map(async (file) => {
      const snaps = snapshots.filter(i => i.file === file)
      const code = await environment.readSnapshotFile(file)
      if (code == null) {
        throw new Error(`cannot read ${file} when saving inline snapshot`)
      }

      const s = new MagicString(code)

      for (const snap of snaps) {
        const index = positionToOffset(code, snap.line, snap.column)
        replaceInlineSnap(code, s, index, snap.snapshot, snap.assertionName)
      }

      const transformed = s.toString()
      if (transformed !== code) {
        await environment.saveSnapshotFile(file, transformed)
      }
    }),
  )
}

const defaultStartObjectRegex

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