Accepted cli/archive/10-scaffold-probes.md

Scaffold tool probes — bun (fail) + git (warn) via Bun.which

This spec encodes [[rfc-bun-which]]. It extends the create-patties

This spec encodes [[rfc-bun-which]]. It extends the create-patties scaffolder ([[cli/archive/05-create-patties]]) with two probe gates: fail on missing bun, warn on missing git.

It is additive to the DX overhaul in [[cli/draft/09-create-patties-dx|spec 09]] — the probes run before the template-copy step regardless of which DX flow is active (legacy flag-driven path or the spec-09 interactive path).

Goal

Stop the scaffolder from running pipeline steps that need binaries the user doesn't have. Give a clear, single-line message instead of letting bun install or git init fail mid-pipeline and leave half a project on disk.

Surface

No new CLI flags. Two probes run silently when their tool is present and emit a single line each when absent.

Probe gates

The probe step runs after argument parsing and directory validation, before the template copy step from [[cli/archive/05-create-patties]]'s Behavior list.

// packages/create-patties/src/probes.ts
export function probeTools(): void {
  if (!Bun.which("bun")) {
    console.error(
      "create-patties: `bun` not found in PATH. " +
      "Install Bun from https://bun.sh and re-run.",
    )
    process.exit(1)
  }
  // git is probed lazily by hasGit() at the git-init step.
}

export function hasGit(): boolean {
  return Bun.which("git") !== null
}

Bun probe (fail)

Bun is required to run the resulting project (bun dev, bun build). If Bun.which("bun") returns null, the scaffolder exits with code 1 and the message above. We do not try to install Bun on the user's behalf.

Edge case: when invoked via bunx create-patties, Bun.which("bun") always returns a path. The probe matters when create-patties is invoked from a shell whose PATH has been clobbered, or when shipped as a standalone binary in the future.

Git probe (warn)

Git is used for the optional git init && git commit step. If Bun.which("git") returns null:

  • Skip the git-init step entirely.
  • Print a single warn line after the scaffold otherwise succeeds: `` create-patties: git not found — skipping git init. ``

The existing --no-git flag continues to skip the git step regardless of probe outcome.

Behavior changes vs [[cli/archive/05-create-patties]]

The Behavior numbered list gains one new step (3a) and amends one existing step (was step 9):

  • 3a. NEW — probeTools() runs. Exits 1 if bun is missing. Runs before any filesystem writes to the target directory.
  • 9. Git step (amended). Unless --no-git is set, and hasGit() returns true, run git init && git add -A && git commit as today. If hasGit() returned false, emit the warn line and skip the git step.

No other Behavior steps change.

Non-goals

  • Probing claude, docker, node, or any other tool. Out of scope. When a patties doctor command spec opens, those probes belong there. This spec consciously stops at the two probes that gate scaffold-time pipeline steps.
  • Auto-installing missing tools. We never try to install bun, git, or anything else on the user's machine.
  • Network probes. No connectivity checks.
  • Bun version-floor enforcement. Bun's presence is what matters here. Version-floor is a separate concern; open a follow-up RFC if we ever ship a feature that requires a minimum Bun version.

Acceptance criteria

  • bunx create-patties foo on a machine with both bun and git completes successfully with no probe messages visible.
  • bunx create-patties foo on a machine with bun but no git completes the scaffold and emits exactly one warn line about git; the target directory contains no .git/.
  • bunx create-patties foo invoked in an environment where Bun.which("bun") returns null exits with code 1 and the error message, having created no files in the target directory.
  • --no-git continues to skip git init even when git is present.

Test plan

  • Unit: stub Bun.which to return null for "bun" → assert probeTools() calls process.exit(1) after printing the error.
  • Unit: stub Bun.which to return null for "git" only → assert hasGit() returns false and the scaffold prints the warn line.
  • Integration: full scaffold in a sandbox where git is removed from PATH → assert no .git/ directory in the result and the warn line appears in stdout.
  • Integration: same, with bun removed from PATH → assert exit 1 and no target directory created.

Out of this spec

A future patties doctor command spec is the right home for richer probes (claude, docker, lockfile freshness, biome config). This spec consciously stops short of inventing that surface.