Vendored Hatch wiring makes every Hatch install fail when the checkout path contains %XX, # or ; (e.g. a Jenkins "feature%2Fx" workspace), because Hatch's {root:uri} only escapes spaces #547

[agent] Found by the scheduled Hatch bug-hunt routine (ledger #314).

Summary

Vendored Hatch wiring writes six @ {root:uri}/.socket/vendor/pypi/<uuid>/<wheel>#sha256=… into project.dependencies and env dependencies / extra-dependencies. docs/testing/hatch.md says this is done "so checkouts remain relocatable". But Hatch/Hatchling expand {root:uri} with hatchling/utils/fs.py:path_to_uri, which only escapes spaces:

def path_to_uri(path: str) -> str:
    if os.sep == "/":
        return f"file://{os.path.abspath(path).replace(' ', '%20')}"
    return f"file:///{os.path.abspath(path).replace(' ', '%20').replace(os.sep, '/')}"

So when the checkout path contains a URL-significant character, the expanded requirement points somewhere else, or doesn't parse at all:

• %2F / %20 / any %XX: pip percent-decodes it, giving …/app_feature/six-patch/.socket/… and OSError: [Errno 2] No such file or directory.
• #: the rest of the path becomes a URL fragment, giving No such file or directory: '/…/a'.
• ;: Invalid requirement: 'six @ file:///…/semi': Expected a marker variable or quoted string.

Jenkins multibranch pipelines put the branch name into the workspace directory with / encoded as %2F (e.g. app_feature%2Fsix-patch), so this is a realistic CI path. The native (unwired) project installs fine in the same directory. Only the socket-patch wiring breaks it.

The scan itself gives no warning, even when it runs from such a path. It reports applied / success.

Impact

• In any checkout whose absolute path contains %XX, # or ;, every Hatch env that carries a vendored reference fails to create (hatch run, hatch env create, hatch test). That includes the default env, because project dependencies go through the same expansion during the dev-mode install. CI goes red, and the cause is far from obvious.
• vex in that checkout still emits not_affected / inline_mitigations_already_exist (from the committed artifact, with only a "live tree does not match" warning), even though no Hatch env can be installed there.
• Hosted mode is unaffected (http URL).

This is the same class as the Maven #350 (file://${project.basedir} not URI-encoded), but in the Hatch lane.

Repro (Linux, Hatch 1.18.1; local mock patch API serving a patched six 1.16.0 wheel, --vendor-source service)

mkdir -p dev/app/src/app && cd dev/app && touch src/app/__init__.py && git init -q
cat > pyproject.toml <<'EOF'
[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"
[project]
name = "app"
version = "0.1.0"
dependencies = ["six==1.16.0"]
[tool.hatch.build.targets.wheel]
packages = ["src/app"]
[tool.hatch.envs.lint]
extra-dependencies = ["six==1.16.0"]
EOF
socket-patch scan --vendor --vendor-source service --json     # applied, success
git add -A && git commit -qm vendored
git clone -q . "../../ws/app_feature%2Fsix-patch" && cd "../../ws/app_feature%2Fsix-patch"
hatch run python -c 'import six'
#   ERROR: Could not install packages due to an OSError: [Errno 2] No such file or directory:
#   '/…/ws/app_feature/six-patch/.socket/vendor/pypi/<uuid>/six-1.16.0-py2.py3-none-any.whl'
hatch run lint:python -c 'import six'                          # same error
git clone -q . ../plain && cd ../plain && hatch run python -c 'import six; print(six.SOCKET_PATCHED)'   # control: True

The same failure happens with the scan run directly inside directories named a#b, p%20q and semi;colon. Directories named at@sign and quo'te work.

Expected vs actual

• Expected: docs/testing/hatch.md: "Vendored references use {root:uri} so checkouts remain relocatable." A vendored scan should either produce wiring that installs from any checkout path, or refuse / warn at scan time when the root contains characters that Hatch's {root:uri} doesn't encode (%, #, ;, ?). It should also document that a checkout can't be relocated to such a path.
• Actual: the scan succeeds silently, and every Hatch env install fails in such checkouts.

OS × Hatch matrix (main 61cfb9b, vendored)

First bad

Present since vendored Hatch landed (#244). Released v4.0.0 has no Hatch lane.

Suspect code

• crates/socket-patch-core/src/vendor/pypi_hatch.rs:46, :95, :180: they emit {root:uri}/… without checking whether the project root is URI-safe for Hatch's expansion.
• crates/socket-patch-core/src/utils/hatch.rs:361 (vendored preflight): it checks the Hatch version but not the root path.
• The root cause is upstream in hatchling/utils/fs.py:path_to_uri (only ' ' is escaped). A scan-time refusal or warning, plus a documented limitation, would avoid silently breaking CI.

Backlog review — 2026-10-08

Priority: P1 → P2. Special checkout-path characters break Hatch installation visibly; constrained path trigger and relocation workaround.