Support annotating a file that contains only a shebang

CHANGELOG.md

@@ -67,6 +67,7 @@ CLI command and its behaviour. There are no guarantees of stability for the
   (#949)
 - The datetime value for `Created:` was wrongly formatted since 3.0.0. It now
   returns a correctly formatted ISO 8601 date again. (#952)
+- Support annotating a file that contains only a shebang. (#965)
 
 ### Security
 

src/reuse/header.py

@@ -216,8 +216,8 @@ def _extract_shebang(prefix: str, text: str) -> Tuple[str, str]:
             shebang_lines.append(line)
             text = text.replace(line, "", 1)
         else:
-            shebang = "\n".join(shebang_lines)
             break
+    shebang = "\n".join(shebang_lines)
     return (shebang, text)
 
 

tests/test_header.py

@@ -1,5 +1,6 @@
 # SPDX-FileCopyrightText: 2019 Free Software Foundation Europe e.V. <https://fsfe.org>
 # SPDX-FileCopyrightText: 2022 Florian Snow <florian@familysnow.net>
+# SPDX-FileCopyrightText: 2024 Carmen Bianca BAKKER <carmenbianca@fsfe.org>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
 
@@ -368,8 +369,10 @@ def test_find_and_replace_separate_shebang():
     assert find_and_replace_header(text, info) == expected
 
 
-def test_find_and_replace_only_shebang():
-    """When the file only contains a shebang, keep it at the top of the file."""
+def test_find_and_replace_shebang_but_no_copyright():
+    """When the file contains a shebang but no copyright information, keep it at
+    the top of the file.
+    """
     info = ReuseInfo({"GPL-3.0-or-later"})
     text = cleandoc(
         """
@@ -395,6 +398,24 @@ def test_find_and_replace_only_shebang():
     assert find_and_replace_header(text, info) == expected
 
 
+def test_find_and_replace_only_shebang():
+    """When the file only contains a shebang, add copyright info below it."""
+    info = ReuseInfo({"GPL-3.0-or-later"})
+    text = "#!/usr/bin/env python3"
+    expected = (
+        cleandoc(
+            """
+            #!/usr/bin/env python3
+
+            # SPDX-License-Identifier: GPL-3.0-or-later
+            """
+        )
+        + "\n"
+    )
+
+    assert find_and_replace_header(text, info) == expected
+
+
 def test_find_and_replace_keep_old_comment():
     """When encountering a comment that does not contain copyright and
     licensing information, preserve it below the REUSE header.