fix(gh-9): require both uv and uvx before skipping bootstrap download

README.md

@@ -216,7 +216,7 @@ isolated      = false
 
 Re-running `install.sh` with the same args is always safe:
 
-- uv download skipped if pinned version already installed
+- uv download skipped only if **both** `uv` and `uvx` are present and `uv` matches the pinned version — a missing `uvx` re-downloads the pair, since they ship in one archive
 - venv creation skipped if `venv/bin/python` already works
 - All generated files (`env.sh`, `env.ps1`, `bin/`, `distro.toml`) are always regenerated (cheap, ensures correctness)
 

TESTING.md

@@ -137,6 +137,43 @@ Values that MUST be rejected: `yesterday`, `1 fortnight`, `P`, `2026-01-01T:`, `
 Values that MUST be accepted: `P1D`, `PT12H`, `P2W`, `P1DT2H`, `3 days`, `2026-01-01`,
 `2026-01-01T00:00:00Z`
 
+### Test 9 — Missing `uvx` forces a re-download
+
+Guards against the bug in [#9](https://github.com/redmatter/managed-python/issues/9): the skip
+condition used to check `uv`'s version only, so a prefix predating `uvx` could keep a broken
+`bin/uvx` forever.
+
+```bash
+./install.sh --prefix /tmp/mp-test --python 3.10 --env-prefix TEST --isolated
+rm -f /tmp/mp-test/uvx /tmp/mp-test/bin/uvx
+./install.sh --prefix /tmp/mp-test --python 3.10 --env-prefix TEST --isolated
+source /tmp/mp-test/env.sh && "$TEST_UVX" --version
+```
+
+**Expect:** the second install prints `→ Downloading uv X.Y.Z` (not `✓ uv X.Y.Z`), keeps
+`✓ venv already exists`, and `$TEST_UVX --version` prints a version rather than
+`No such file or directory`.
+
+Then re-run Test 3 — a **complete** prefix must still print `✓ uv X.Y.Z` and skip the download.
+
+### Test 10 — setup.py refuses to wrap a missing binary
+
+`setup.py` will not create a wrapper pointing at thin air, even when run on its own.
+
+```bash
+mv /tmp/mp-test/uvx /tmp/uvx.bak
+/tmp/mp-test/venv/bin/python setup.py --prefix /tmp/mp-test --python 3.10 --env-prefix TEST --isolated
+echo "exit=$?"
+mv /tmp/uvx.bak /tmp/mp-test/uvx
+```
+
+**Expect:** exits `1` with `ERROR: bootstrap incomplete - these are missing from the prefix:`
+naming `uvx`, before any `==>` step header is printed, and with **no** `bin/` wrappers or env
+files rewritten.
+
+A missing `uv` must be caught the same way — that ordering matters, because cooldown validation
+silently no-ops when `uv` cannot be run.
+
 ---
 
 ## Windows (PowerShell)
@@ -205,6 +242,20 @@ Select-String cooldown C:\Users\Quickemu\temp\mp-test\distro.toml
 
 Repeat with `-Cooldown "P0D"` and expect both assignments commented out.
 
+### Windows: Test 6 — Missing `uvx.exe` forces a re-download
+
+The Windows half of Test 9.
+
+```powershell
+Remove-Item C:\Users\Quickemu\temp\mp-test\uvx.exe, C:\Users\Quickemu\temp\mp-test\bin\uvx.cmd -Force
+.\install.ps1 -Prefix "C:\Users\Quickemu\temp\mp-test" -Python "3.10" -EnvPrefix "TEST"
+. C:\Users\Quickemu\temp\mp-test\env.ps1
+& $env:TEST_UVX --version
+```
+
+**Expect:** `→ Downloading uv X.Y.Z` rather than `✓ uv X.Y.Z`, `✓ venv already exists`, and
+`uvx --version` prints a version. Re-running on the restored prefix must skip the download again.
+
 ---
 
 ## Testing from a release ZIP

install.ps1

@@ -52,6 +52,7 @@ $ErrorActionPreference = "Stop"
 $Prefix    = [Environment]::ExpandEnvironmentVariables($Prefix)
 $ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
 $UvExe     = Join-Path $Prefix "uv.exe"
+$UvxExe    = Join-Path $Prefix "uvx.exe"
 $VenvPy    = Join-Path $Prefix "venv\Scripts\python.exe"
 
 # Read pinned uv version from distro.toml
@@ -67,7 +68,9 @@ Write-Msg ""
 
 # Bootstrap uv
 $currentVer = if (Test-Path $UvExe) { try { (& $UvExe --version 2>$null) -split " " | Select-Object -Last 1 } catch { "" } } else { "" }
-if ($currentVer -eq $UvVersion) {
+# uvx.exe must exist too - a prefix predating uvx can match the pinned version
+# while missing it entirely, and skipping the download would leave it that way.
+if (($currentVer -eq $UvVersion) -and (Test-Path $UvxExe)) {
     Write-Msg "  ✓ uv $UvVersion"
 } else {
     Write-Msg "  → Downloading uv $UvVersion"
@@ -96,7 +99,7 @@ if ($currentVer -eq $UvVersion) {
         Copy-Item $uvSrc.FullName $UvExe -Force
         $uvxSrc = Get-ChildItem $tmpDir -Filter "uvx.exe" -Recurse | Select-Object -First 1
         if (-not $uvxSrc) { Write-Error "Failed to locate uvx.exe in archive"; exit 1 }
-        Copy-Item $uvxSrc.FullName (Join-Path $Prefix "uvx.exe") -Force
+        Copy-Item $uvxSrc.FullName $UvxExe -Force
     } catch {
         Write-Error "Failed to download uv $UvVersion from $url`: $_"
         exit 1
@@ -107,6 +110,10 @@ if ($currentVer -eq $UvVersion) {
         Write-Error "Failed to download uv $UvVersion — binary not found after extraction"
         exit 1
     }
+    if (-not (Test-Path $UvxExe)) {
+        Write-Error "Failed to download uv $UvVersion — uvx.exe not found after extraction"
+        exit 1
+    }
     Write-Msg "  ✓ uv $UvVersion installed"
 }
 

install.sh

@@ -39,7 +39,11 @@ _bootstrap_uv() {
     local prefix="$1" uv_version="$2" distro_toml="$3"
     local uv_bin="${prefix}/uv"
 
-    if [[ -x "$uv_bin" ]] && \
+    # Both binaries must be present, not just uv - a prefix from before uvx
+    # existed can match the pinned version yet have no uvx at all, and a
+    # version-only check would happily skip the download and leave it missing.
+    # A missing uvx therefore re-downloads the pair; they ship in one archive.
+    if [[ -x "$uv_bin" ]] && [[ -x "${prefix}/uvx" ]] && \
        [[ "$("$uv_bin" --version 2>/dev/null | awk '{print $2}')" == "$uv_version" ]]; then
         _msg "  ✓ uv $uv_version"; return
     fi

setup.py

@@ -220,6 +220,34 @@ def _symlink(link: Path, target: Path) -> None:
     link.symlink_to(target)
 
 
+def _require_bootstrapped(prefix: Path) -> None:
+    """Fail loudly if the bootstrap phase did not leave every binary behind.
+
+    A wrapper pointing at thin air is never a valid outcome: on POSIX it is a
+    dangling symlink, on Windows a .cmd that fails later with a baffling error.
+    Better to stop here, while the cause is still obvious.
+
+    Args:
+        prefix: The install prefix that the bootstrap phase populated.
+
+    Raises:
+        SystemExit: Exit code 1 when any expected binary is missing.
+    """
+    if _IS_WINDOWS:
+        expected = [prefix / "uv.exe", prefix / "uvx.exe", prefix / "venv" / "Scripts" / "python.exe"]
+    else:
+        expected = [prefix / "uv", prefix / "uvx", prefix / "venv" / "bin" / "python"]
+    missing = [p for p in expected if not p.exists()]
+    if missing:
+        listed = "\n".join(f"  {p}" for p in missing)
+        print(
+            f"ERROR: bootstrap incomplete - these are missing from the prefix:\n{listed}\n"
+            "       Re-run the installer to fetch them before configuring this prefix.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+
 def _create_bin(prefix: Path) -> None:
     _step("Creating bin/ wrappers")
     bin_dir = prefix / "bin"
@@ -517,6 +545,9 @@ def main() -> None:
 
     # Validate before writing anything — a bad cooldown would otherwise poison
     # every uv invocation of everyone who sources the generated env files.
+    # Order matters: the bootstrap check runs first so that uv is known to be
+    # present, otherwise _validate_cooldown quietly skips validation entirely.
+    _require_bootstrapped(prefix)
     rejection = _validate_cooldown(prefix, args.cooldown)
     if rejection:
         print(f"ERROR: --cooldown {args.cooldown!r} was rejected by uv:\n  {rejection}", file=sys.stderr)