Neither nor found; the deprecation fragment system is not…

Error message

Neither {} nor {} found; the deprecation fragment system is not installed in this repo.

What it means

Thrown by `cargo vdev deprecation check` (exec) when neither the deprecation fragments directory nor the generated deprecations JSON file exists in the repository, meaning the deprecation fragment system has not been installed/set up in this repo. The check cannot proceed without at least one of these inputs.

Solutions

Switch to a branch/checkout that contains the deprecation fragment system.
Run `cargo vdev deprecation generate` after restoring the fragments directory to create the JSON.
Verify the repo root was detected correctly (paths::find_repo_root) — run from the repo root.
If this repo intentionally has no deprecations, skip the check instead of running it.

Example fix

// before (fresh clone missing files)
cargo vdev deprecation check
// after
git checkout main
cargo vdev deprecation generate && cargo vdev deprecation check

Defensive patterns

Strategy: fallback

Validate before calling

use std::path::Path;
let dir = repo_root.join("deprecations");
let json = repo_root.join("deprecations.json");
if !dir.is_dir() && !json.is_file() { eprintln!("deprecation system not installed; skipping check"); return; }

Type guard

fn deprecation_system_installed(repo_root: &Path) -> bool { repo_root.join("deprecations").is_dir() || repo_root.join("deprecations.json").is_file() }

Try / catch

match result { Err(e) if e.to_string().contains("deprecation fragment system is not installed") => { /* treat as skip/no-op in CI */ } Err(e) => return Err(e), Ok(v) => v }

Prevention

Check the repo contains the deprecation directory before wiring the check into CI
Run commands from the repository root
Keep branches synced with upstream so the deprecation system files exist

When it happens

Trigger: Running `cargo vdev deprecation check` in a repo checkout where the DEPRECATION_DIR directory is missing AND the DEPRECATIONS_JSON file is missing (both is_dir() and is_file() checks fail).

Common situations: Occurs in shallow/partial checkouts, older branches before the deprecation system was introduced, or forks that stripped the deprecation directory.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/6abce1feda6692f5. Report an issue: GitHub.

Appendix: source

Thrown at vdev/src/commands/deprecation/check.rs:29

#[command()]
pub struct Cli {}

impl Cli {
    pub fn exec(self) -> Result<()> {
        let repo_root = paths::find_repo_root()?;
        let dir = repo_root.join(deprecation::DEPRECATION_DIR);

        let json_path = repo_root.join(deprecation::DEPRECATIONS_JSON);
        let entries = if dir.is_dir() {
            deprecation::read_deprecation_fragments(&dir)?
        } else if json_path.is_file() {
            println!(
                "{} not found; validating generated JSON only.",
                dir.display()
            );
            Vec::new()
        } else {
            bail!(
                "Neither {} nor {} found; the deprecation fragment system is not installed in this repo.",
                dir.display(),
                json_path.display()
            );
        };

        if entries.is_empty() {
            println!("No deprecation fragments found.");
        } else {
            for entry in &entries {
                println!("  ok  {}", entry.filename);
            }
            println!("{} deprecation fragment(s) are valid.", entries.len());
        }

        // Reject any fragment with a deprecated_since newer than the next
        // minor release. Skipped (with a warning) when the checkout has no
        // release tags so shallow CI/source checkouts can still validate

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