fix: buffer CLI stdin before format detection on Windows

packages/markitdown/src/markitdown/__main__.py

@@ -5,6 +5,7 @@
 import os
 import sys
 import codecs
+import io
 from typing import Any, Dict
 from textwrap import dedent
 from importlib.metadata import entry_points
@@ -248,8 +249,9 @@ def main():
         markitdown = MarkItDown(enable_plugins=args.use_plugins)
 
     if args.filename is None:
+        # Windows pipe-backed stdin can report seekable() even though it cannot rewind.
         result = markitdown.convert_stream(
-            sys.stdin.buffer,
+            io.BytesIO(sys.stdin.buffer.read()),
             stream_info=stream_info,
             keep_data_uris=args.keep_data_uris,
         )

packages/markitdown/tests/test_cli_misc.py

@@ -1,14 +1,21 @@
 #!/usr/bin/env python3 -m pytest
+import io
 import subprocess
+import sys
+from types import SimpleNamespace
+
 from markitdown import __version__
+from markitdown.__main__ import main
 
 # This file contains CLI tests that are not directly tested by the FileTestVectors.
 # This includes things like help messages, version numbers, and invalid flags.
 
 
 def test_version() -> None:
     result = subprocess.run(
-        ["python", "-m", "markitdown", "--version"], capture_output=True, text=True
+        [sys.executable, "-m", "markitdown", "--version"],
+        capture_output=True,
+        text=True,
     )
 
     assert result.returncode == 0, f"CLI exited with error: {result.stderr}"
@@ -17,7 +24,9 @@ def test_version() -> None:
 
 def test_invalid_flag() -> None:
     result = subprocess.run(
-        ["python", "-m", "markitdown", "--foobar"], capture_output=True, text=True
+        [sys.executable, "-m", "markitdown", "--foobar"],
+        capture_output=True,
+        text=True,
     )
 
     assert result.returncode != 0, f"CLI exited with error: {result.stderr}"
@@ -27,6 +36,25 @@ def test_invalid_flag() -> None:
     assert "SYNTAX" in result.stderr, "Expected 'SYNTAX' to appear in STDERR"
 
 
+def test_windows_pipe_input_is_buffered_before_conversion(monkeypatch, capsys) -> None:
+    class WindowsPipe(io.BytesIO):
+        def seek(self, offset: int, whence: int = io.SEEK_SET) -> int:
+            if whence == io.SEEK_END:
+                return super().seek(offset, whence)
+            return 0
+
+    stdin = SimpleNamespace(
+        buffer=WindowsPipe(b"<html><body><h1>Test HTML</h1></body></html>")
+    )
+    monkeypatch.setattr(sys, "stdin", stdin)
+    monkeypatch.setattr(sys, "argv", ["markitdown", "-x", "html"])
+
+    main()
+
+    captured = capsys.readouterr()
+    assert captured.out.strip() == "# Test HTML"
+
+
 if __name__ == "__main__":
     """Runs this file's tests from the command line."""
     test_version()

packages/markitdown/tests/test_cli_vectors.py

@@ -4,6 +4,7 @@
 import pytest
 import subprocess
 import locale
+import sys
 from typing import List
 
 if __name__ == "__main__":
@@ -46,7 +47,7 @@ def test_output_to_stdout(shared_tmp_dir, test_vector) -> None:
 
     result = subprocess.run(
         [
-            "python",
+            sys.executable,
             "-m",
             "markitdown",
             os.path.join(TEST_FILES_DIR, test_vector.filename),
@@ -69,7 +70,7 @@ def test_output_to_file(shared_tmp_dir, test_vector) -> None:
     output_file = os.path.join(shared_tmp_dir, test_vector.filename + ".output")
     result = subprocess.run(
         [
-            "python",
+            sys.executable,
             "-m",
             "markitdown",
             "-o",
@@ -83,7 +84,7 @@ def test_output_to_file(shared_tmp_dir, test_vector) -> None:
     assert result.returncode == 0, f"CLI exited with error: {result.stderr}"
     assert os.path.exists(output_file), f"Output file not created: {output_file}"
 
-    with open(output_file, "r") as f:
+    with open(output_file, "r", encoding="utf-8") as f:
         output_data = f.read()
         for test_string in test_vector.must_include:
             assert test_string in output_data
@@ -104,10 +105,9 @@ def test_input_from_stdin_without_hints(shared_tmp_dir, test_vector) -> None:
 
     result = subprocess.run(
         [
-            "python",
+            sys.executable,
             "-m",
             "markitdown",
-            os.path.join(TEST_FILES_DIR, test_vector.filename),
         ],
         input=test_input,
         capture_output=True,
@@ -135,7 +135,12 @@ def test_convert_url(shared_tmp_dir, test_vector):
 
     time.sleep(1)  # Ensure we don't hit rate limits
     result = subprocess.run(
-        ["python", "-m", "markitdown", TEST_FILES_URL + "/" + test_vector.filename],
+        [
+            sys.executable,
+            "-m",
+            "markitdown",
+            TEST_FILES_URL + "/" + test_vector.filename,
+        ],
         capture_output=True,
         text=False,
     )
@@ -155,7 +160,7 @@ def test_output_to_file_with_data_uris(shared_tmp_dir, test_vector) -> None:
     output_file = os.path.join(shared_tmp_dir, test_vector.filename + ".output")
     result = subprocess.run(
         [
-            "python",
+            sys.executable,
             "-m",
             "markitdown",
             "--keep-data-uris",
@@ -170,7 +175,7 @@ def test_output_to_file_with_data_uris(shared_tmp_dir, test_vector) -> None:
     assert result.returncode == 0, f"CLI exited with error: {result.stderr}"
     assert os.path.exists(output_file), f"Output file not created: {output_file}"
 
-    with open(output_file, "r") as f:
+    with open(output_file, "r", encoding="utf-8") as f:
         output_data = f.read()
         for test_string in test_vector.must_include:
             assert test_string in output_data

packages/markitdown/tests/test_cu_converter.py

@@ -932,11 +932,11 @@ def test_use_cu_reads_from_stdin(self, capsys):
             enable_plugins=False,
             cu_endpoint="https://fake-cu",
         )
-        markitdown_instance.convert_stream.assert_called_once_with(
-            input_buffer,
-            stream_info=None,
-            keep_data_uris=False,
-        )
+
+        assert markitdown_instance.convert_stream.call_count == 1
+        call_args, call_kwargs = markitdown_instance.convert_stream.call_args
+        assert call_args[0].read() == b"fake pdf"
+        assert call_kwargs == {"stream_info": None, "keep_data_uris": False}
         assert capsys.readouterr().out == "converted\n"