How I Handle Recursive Config Discovery in CLI Tools

My Approach

When writing CLI tools, especially ones that interact with structured content like Markdown files or docs sites, I like to keep config discovery intuitive. Rather than forcing users to pass a path to a config file every time, I just have the tool look for something like frontMatterHelper.json automatically.

The logic is simple:

• Start in the current directory.
• Keep going up the parent directories until you find the file.
• If you hit the filesystem root without finding it, throw an error.

This lets users run the CLI tool from any subfolder in a project and still have the config file picked up correctly — as long as it's somewhere up the tree. Think of it like how git finds your .git directory. It's one of those invisible but expected conveniences.

Once I find the config file, I just cache the full path in memory so the tool can use it as needed. I haven't had to persist it between runs yet, but if I did, I’d probably use an env var or stash it in a tmp file (but that hasn’t really come up).

---

What ChatGPT Added

When I asked ChatGPT how to formalize or document this behavior, here's the breakdown it gave:

🔍 Recursive Search Strategy

1. Starting Point: Begin at the current working directory.

2. Loop Upward: At each level, check if frontMatterHelper.json exists.

3. Stop Conditions:

   • If found: return the path.
   • If at filesystem root and not found: throw or prompt the user.

📦 Suggested Implementation (Node.js example)

function findConfigFile(currentDir) {
  const configFile = "frontMatterHelper.json";
  let parentDir = path.resolve(currentDir, "..");
  let configPath = path.join(currentDir, configFile);

  if (fs.existsSync(configPath)) {
    return configPath;
  } else if (parentDir === currentDir) {
    throw new Error("Configuration file not found.");
  } else {
    return findConfigFile(parentDir);
  }
}

const configFilePath = findConfigFile(process.cwd());

🧠 Suggestions for Persisting the Location

ChatGPT listed a few options for retaining the config file path across executions:

• In-memory: Good enough for short-running CLI tools.
• Environment Variable: Useful if you're calling subcommands or scripts that also need it.
• Temporary File: Maybe overkill for most CLI use cases, but handy if multiple processes need to share it.