fix(lib): concat list entries broke on relative paths and quotes in paths

CHANGELOG.md

@@ -35,6 +35,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   [@lapotist](https://github.com/lapotist) [#664](https://github.com/jeertmans/manim-slides/pull/664)
 - Fixed presenter looping when reversing multiple slides.
   [@wuerfelfreak](https://github.com/wuerfelfreak) [#665](https://github.com/jeertmans/manim-slides/pull/665)
+- Fixed `concatenate_video_files` failing on relative input paths and on paths containing single quotes, by writing absolute, properly escaped entries to the concat list file.
+  [@Agi-Asi](https://github.com/Agi-Asi) [#673](https://github.com/jeertmans/manim-slides/pull/673)
 
 (v5.6.0)=
 ## [v5.6.0](https://github.com/jeertmans/manim-slides/compare/v5.5.4...v5.6.0)

manim_slides/utils.py

@@ -54,7 +54,12 @@ def _filter(files: list[Path]) -> Iterator[Path]:
     with tempfile.NamedTemporaryFile(
         mode="w", suffix=".txt", delete=False, encoding="utf-8"
     ) as f:
-        f.writelines(f"file '{file}'\n" for file in _filter(files))
+        # Write absolute paths and escape single quotes ('\'') so that ffmpeg's
+        # concat demuxer parses every entry correctly, see #673.
+        f.writelines(
+            "file '{}'\n".format(file.resolve().as_posix().replace("'", "'\\''"))
+            for file in _filter(files)
+        )
         tmp_file = f.name
 
     with (

tests/test_utils.py

@@ -1,6 +1,10 @@
+import shutil
 from pathlib import Path
 
-from manim_slides.utils import merge_basenames
+import av
+import pytest
+
+from manim_slides.utils import concatenate_video_files, merge_basenames
 
 
 def test_merge_basenames(paths: list[Path]) -> None:
@@ -20,3 +24,38 @@ def test_merge_basenames_same_with_different_parent_directories(
     p4 = d2 / "d/e/f/two.txt"
 
     assert merge_basenames([p1, p2]).name == merge_basenames([p3, p4]).name
+
+
+def assert_has_decodable_video_stream(dest: Path) -> None:
+    assert dest.exists()
+    with av.open(str(dest)) as container:
+        assert sum(1 for _ in container.decode(video=0)) > 0
+
+
+def test_concatenate_video_files_relative_paths(
+    video_file: Path, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    # The concat list file lives in the system temp folder, and the concat
+    # demuxer resolves relative entries against *that* folder — so relative
+    # input paths used to fail with FileNotFoundError.
+    monkeypatch.chdir(video_file.parent)
+    relative = Path(video_file.name)
+    dest = tmp_path / "out.mp4"
+
+    concatenate_video_files([relative, relative], dest)
+
+    assert_has_decodable_video_stream(dest)
+
+
+def test_concatenate_video_files_quoted_path(video_file: Path, tmp_path: Path) -> None:
+    # A single quote in a path used to terminate the quoted list entry early,
+    # making the entry unparsable for the concat demuxer.
+    quoted_dir = tmp_path / "John's slides"
+    quoted_dir.mkdir()
+    src = quoted_dir / video_file.name
+    shutil.copy(video_file, src)
+    dest = tmp_path / "out.mp4"
+
+    concatenate_video_files([src, src], dest)
+
+    assert_has_decodable_video_stream(dest)