fix: fall back to feature dir basename for empty CURRENT_BRANCH (#3026)

scripts/bash/common.sh

@@ -186,6 +186,15 @@ get_feature_paths() {
         return 1
     fi
 
+    # When no branch context exists (no SPECIFY_FEATURE, feature resolved via
+    # SPECIFY_FEATURE_DIRECTORY or feature.json), fall back to the feature
+    # directory basename so CURRENT_BRANCH is a usable identifier rather than
+    # an empty, misleading value (issue #3026).
+    if [[ -z "$current_branch" ]]; then
+        local feature_dir_trimmed="${feature_dir%/}"
+        current_branch="${feature_dir_trimmed##*/}"
+    fi
+
     # Use printf '%q' to safely quote values, preventing shell injection
     # via crafted branch names or paths containing special characters
     printf 'REPO_ROOT=%q\n' "$repo_root"

scripts/powershell/common.ps1

@@ -182,6 +182,17 @@ function Get-FeaturePathsEnv {
         exit 1
     }
 
+    # When no branch context exists (no SPECIFY_FEATURE, feature resolved via
+    # SPECIFY_FEATURE_DIRECTORY or feature.json), fall back to the feature
+    # directory basename so CURRENT_BRANCH is a usable identifier rather than
+    # an empty, misleading value (issue #3026).
+    if (-not $currentBranch) {
+        # TrimEnd (not [Path]::TrimEndingDirectorySeparator, which is .NET Core
+        # only) keeps this working on Windows PowerShell 5.1 / .NET Framework.
+        $featureDirTrimmed = $featureDir.TrimEnd('/', '\')
+        $currentBranch = Split-Path -Leaf $featureDirTrimmed
+    }
+
     [PSCustomObject]@{
         REPO_ROOT     = $repoRoot
         CURRENT_BRANCH = $currentBranch

tests/test_check_prerequisites_paths_only.py

@@ -121,6 +121,45 @@ def test_paths_only_succeeds_on_spec_branch(prereq_repo: Path) -> None:
     assert "001-my-feature" in data.get("BRANCH", "")
 
 
+@requires_bash
+@pytest.mark.parametrize(
+    ("use_env_var", "specify_feature", "expected_branch"),
+    [
+        (False, None, "001-my-feature"),
+        (True, None, "001-my-feature"),
+        (False, "my-explicit-branch", "my-explicit-branch"),
+    ],
+    ids=["feature_json", "env_var", "explicit_feature"],
+)
+def test_current_branch_falls_back_to_feature_dir_basename(
+    prereq_repo: Path, use_env_var: bool, specify_feature: str | None, expected_branch: str
+) -> None:
+    """With no SPECIFY_FEATURE, BRANCH falls back to the feature directory
+    basename (from feature.json or SPECIFY_FEATURE_DIRECTORY) instead of being
+    emitted empty. If SPECIFY_FEATURE is set, it remains authoritative (#3026)."""
+    feat = prereq_repo / "specs" / "001-my-feature"
+    feat.mkdir(parents=True, exist_ok=True)
+    env = _clean_env()
+    if specify_feature:
+        env["SPECIFY_FEATURE"] = specify_feature
+    if use_env_var:
+        env["SPECIFY_FEATURE_DIRECTORY"] = "specs/001-my-feature"
+    else:
+        _write_feature_json(prereq_repo)
+    script = prereq_repo / ".specify" / "scripts" / "bash" / "check-prerequisites.sh"
+    result = subprocess.run(
+        ["bash", str(script), "--json", "--paths-only"],
+        cwd=prereq_repo,
+        capture_output=True,
+        text=True,
+        check=False,
+        env=env,
+    )
+    assert result.returncode == 0, result.stderr
+    data = json.loads(result.stdout)
+    assert data["BRANCH"] == expected_branch
+
+
 @requires_bash
 def test_paths_only_text_mode_on_non_spec_branch(prereq_repo: Path) -> None:
     """--paths-only without --json must return text paths from feature.json."""
@@ -189,6 +228,46 @@ def test_ps_paths_only_succeeds_on_non_spec_branch(prereq_repo: Path) -> None:
     assert "FEATURE_DIR" in data
 
 
+@pytest.mark.skipif(not (HAS_PWSH or _WINDOWS_POWERSHELL), reason="no PowerShell available")
+@pytest.mark.parametrize(
+    ("use_env_var", "specify_feature", "expected_branch"),
+    [
+        (False, None, "001-my-feature"),
+        (True, None, "001-my-feature"),
+        (False, "my-explicit-branch", "my-explicit-branch"),
+    ],
+    ids=["feature_json", "env_var", "explicit_feature"],
+)
+def test_ps_current_branch_falls_back_to_feature_dir_basename(
+    prereq_repo: Path, use_env_var: bool, specify_feature: str | None, expected_branch: str
+) -> None:
+    """With no SPECIFY_FEATURE, BRANCH falls back to the feature directory
+    basename (from feature.json or SPECIFY_FEATURE_DIRECTORY) instead of being
+    emitted empty. If SPECIFY_FEATURE is set, it remains authoritative (#3026)."""
+    feat = prereq_repo / "specs" / "001-my-feature"
+    feat.mkdir(parents=True, exist_ok=True)
+    env = _clean_env()
+    if specify_feature:
+        env["SPECIFY_FEATURE"] = specify_feature
+    if use_env_var:
+        env["SPECIFY_FEATURE_DIRECTORY"] = "specs/001-my-feature"
+    else:
+        _write_feature_json(prereq_repo)
+    script = prereq_repo / ".specify" / "scripts" / "powershell" / "check-prerequisites.ps1"
+    exe = "pwsh" if HAS_PWSH else _WINDOWS_POWERSHELL
+    result = subprocess.run(
+        [exe, "-NoProfile", "-File", str(script), "-Json", "-PathsOnly"],
+        cwd=prereq_repo,
+        capture_output=True,
+        text=True,
+        check=False,
+        env=env,
+    )
+    assert result.returncode == 0, result.stderr
+    data = json.loads(result.stdout)
+    assert data["BRANCH"] == expected_branch
+
+
 @pytest.mark.skipif(not (HAS_PWSH or _WINDOWS_POWERSHELL), reason="no PowerShell available")
 def test_ps_paths_only_succeeds_on_spec_branch(prereq_repo: Path) -> None:
     """-PathsOnly must also work when feature.json and SPECIFY_FEATURE agree."""