fix(scripts): fall through to grep/sed when python3 is a broken stub in feature.json parser (#3312)

* fix(scripts): fall through to grep/sed when python3 is a broken stub in feature.json parser

read_feature_json_feature_directory picked its json parser by availability
(if jq / elif python3 / else grep-sed). on windows `python3` usually resolves
to the microsoft store app execution alias stub: it satisfies `command -v` but
fails at runtime (exit 49). the elif selected it, the runtime failure was
swallowed to _fd='', and the grep/sed last resort was never reached - so a
valid .specify/feature.json read as empty and every setup-plan / setup-tasks /
check-prerequisites call errored with "Feature directory not found" right after
a successful `specify init --script sh`.

change selection from availability to parse success: try jq, then python3 only
if still empty, then grep/sed only if still empty. a parser that exists but
produces nothing now falls through instead of terminating the chain.

the write path (_persist_feature_json) already uses jq-or-printf with no
python3, so it was unaffected; only the read path needed this.

add a regression test that puts a python3 stub (exit 49, like the store alias)
first on PATH and asserts setup-plan.sh still resolves the feature via the
grep/sed fallback.

fixes #3304

* test: shadow jq so the broken-python3 fallback test actually exercises it

the test claimed it dropped jq so the parser chain would reach python3 and
then grep/sed, but it only prepended the python3 stub dir to PATH. on a
runner with jq installed, read_feature_json_feature_directory parses via jq
and never reaches the fallback the test is meant to cover.

add a failing jq stub alongside the python3 stub so the chain is forced
through jq -> python3 -> grep/sed regardless of what the runner has installed.

scripts/bash/common.sh

@@ -97,17 +97,26 @@ read_feature_json_feature_directory() {
     local fj="$repo_root/.specify/feature.json"
     [[ -f "$fj" ]] || { printf '%s' ''; return 0; }
 
+    # Try parsers in order (jq -> python3 -> grep/sed), falling through on
+    # failure. Selection is by *parse success*, not mere availability: on
+    # Windows `python3` commonly resolves to the Microsoft Store App Execution
+    # Alias stub, which passes `command -v` but fails at runtime (exit 49), so
+    # an availability-gated `elif` would pick python3, swallow its failure, and
+    # never reach the grep/sed fallback -- leaving feature.json unreadable even
+    # though it is valid (issue #3304).
     local _fd=''
     if command -v jq >/dev/null 2>&1; then
         if ! _fd=$(jq -r '.feature_directory // empty' "$fj" 2>/dev/null); then
             _fd=''
         fi
-    elif command -v python3 >/dev/null 2>&1; then
+    fi
+    if [[ -z "$_fd" ]] && command -v python3 >/dev/null 2>&1; then
         # Use Python so pretty-printed/multi-line JSON still parses correctly.
         if ! _fd=$(python3 -c "import json,sys; d=json.load(open(sys.argv[1])); v=d.get('feature_directory'); print(v if v else '')" "$fj" 2>/dev/null); then
             _fd=''
         fi
-    else
+    fi
+    if [[ -z "$_fd" ]]; then
         # Last-resort single-line grep/sed fallback. The `|| true` guards against
         # grep returning 1 (no match) aborting under `set -e` / `pipefail`.
         _fd=$( { grep -E '"feature_directory"[[:space:]]*:' "$fj" 2>/dev/null || true; } \

tests/test_setup_plan_feature_json.py

@@ -126,6 +126,71 @@ def test_setup_plan_errors_without_feature_context(plan_repo: Path) -> None:
     assert "Feature directory not found" in result.stderr
 
 
+@requires_bash
+def test_setup_plan_survives_broken_python3_stub(plan_repo: Path) -> None:
+    """A `python3` on PATH that exists but fails at runtime must not defeat
+    feature.json parsing.
+
+    On Windows `python3` typically resolves to the Microsoft Store App Execution
+    Alias stub: it satisfies `command -v python3` yet exits non-zero at runtime.
+    The parser must fall through to the grep/sed fallback on that failure instead
+    of selecting python3 by mere availability and swallowing its error (#3304).
+    """
+    subprocess.run(
+        ["git", "checkout", "-q", "-b", "feature/my-feature-branch"],
+        cwd=plan_repo,
+        check=True,
+    )
+    feat = plan_repo / "specs" / "001-tiny-notes-app"
+    feat.mkdir(parents=True)
+    (feat / "spec.md").write_text("# spec\n", encoding="utf-8")
+    _write_feature_json(plan_repo, "specs/001-tiny-notes-app")
+
+    # A stub python3 that mimics the Windows Store alias: on PATH, exits 49.
+    stub_dir = plan_repo / "_stubbin"
+    stub_dir.mkdir()
+    stub = stub_dir / "python3"
+    stub.write_text(
+        "#!/bin/sh\n"
+        'echo "Python was not found; run without arguments to install from the '
+        'Microsoft Store" >&2\n'
+        "exit 49\n",
+        encoding="utf-8",
+    )
+    stub.chmod(0o755)
+
+    # A stub jq that shadows any real jq on PATH and also fails, so the parser
+    # cannot short-circuit on jq and must reach the broken python3 stub and then
+    # fall through to grep/sed. Without this, a runner that has jq installed
+    # would parse feature.json via jq and never exercise the fallback this test
+    # is meant to cover.
+    jq_stub = stub_dir / "jq"
+    jq_stub.write_text(
+        "#!/bin/sh\n"
+        'echo "jq: simulated failure" >&2\n'
+        "exit 1\n",
+        encoding="utf-8",
+    )
+    jq_stub.chmod(0o755)
+
+    env = _clean_env()
+    # Prepend the stub dir so the failing jq and python3 stubs take precedence
+    # over any real ones; PATH still needs the real bash utilities for grep/sed.
+    env["PATH"] = f"{stub_dir}{os.pathsep}{env.get('PATH', '')}"
+
+    script = plan_repo / ".specify" / "scripts" / "bash" / "setup-plan.sh"
+    result = subprocess.run(
+        ["bash", str(script)],
+        cwd=plan_repo,
+        capture_output=True,
+        text=True,
+        check=False,
+        env=env,
+    )
+    assert result.returncode == 0, result.stderr + result.stdout
+    assert (feat / "plan.md").is_file()
+
+
 @requires_bash
 def test_setup_plan_numbered_branch_works_with_feature_json(
     plan_repo: Path,