Normalize firmware DB paths to POSIX format for cross-platform compatibility (#92)

* Initial plan

* fix: normalize firmware paths to POSIX format for cross-platform DB compatibility

Use .as_posix() instead of str() when storing and comparing relative
firmware paths in the database. This prevents path separator mismatches
(backslash vs forward slash) when the same firmware folder is accessed
from both Windows and Linux/WSL2.

Fixes: Windows/Linux conflicts in mpflash database

Agent-Logs-Url: https://github.com/Josverl/mpflash/sessions/b370abd5-407c-4f64-9aa2-03ffefb02d91

Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Author: Copilot

mpflash/download/from_web.py

@@ -187,7 +187,7 @@ def fetch_firmware_files(available_firmwares: List[Firmware], firmware_folder: P
             r = requests.get(board.source, allow_redirects=True)
             with open(filename, "wb") as fw:
                 fw.write(r.content)
-            board.firmware_file = str(filename.relative_to(firmware_folder))
+            board.firmware_file = filename.relative_to(firmware_folder).as_posix()
         except requests.RequestException as e:
             log.exception(e)
             continue

mpflash/downloaded.py

@@ -25,7 +25,7 @@ def clean_downloaded_firmwares() -> None:
     firmware_dir = Path(config.firmware_folder)
 
     firmware_files_on_disk = {
-        str(f.relative_to(firmware_dir)) for f in firmware_dir.rglob("*") if f.is_file() and f.suffix not in {".db", ".bak", ".jsonl"}
+        f.relative_to(firmware_dir).as_posix() for f in firmware_dir.rglob("*") if f.is_file() and f.suffix not in {".db", ".bak", ".jsonl"}
     }
 
     with database.atomic():

tests/test_downloaded.py

@@ -1,10 +1,13 @@
+from pathlib import Path
+from unittest.mock import patch
+
 import pytest
 from pytest_mock import MockerFixture
 
 from mpflash.db.models import Firmware
 
 # from mpflash.db.downloads import downloaded_fw
-from mpflash.downloaded import find_downloaded_firmware
+from mpflash.downloaded import clean_downloaded_firmwares, find_downloaded_firmware
 from mpflash.versions import clean_version
 
 pytestmark = [pytest.mark.mpflash]
@@ -147,3 +150,77 @@ def test_find_downloaded_firmware_preview_no_port(mocker: MockerFixture, session
     assert result, "Should find preview firmware even without port"
     fw = result[0]
     assert "preview" in fw.firmware_file
+
+
+def test_clean_downloaded_firmwares_uses_posix_paths(tmp_path):
+    """Ensure clean_downloaded_firmwares uses POSIX paths for cross-platform DB compat.
+
+    On Windows, Path.relative_to() produces backslash separators which would
+    mismatch DB records stored with forward slashes (e.g. from Linux/WSL2).
+    The fix normalises disk paths to POSIX before comparing with the DB.
+    """
+    from mpflash.db.models import Board, Firmware, Metadata, database
+
+    # Initialize the shared database to an in-memory instance
+    if not database.is_closed():
+        database.close()
+    database.init(":memory:")
+    database.connect()
+    database.create_tables([Metadata, Board, Firmware])
+
+    try:
+        # Create a firmware file on disk
+        fw_dir = tmp_path / "esp32"
+        fw_dir.mkdir()
+        fw_file = fw_dir / "ESP32_GENERIC-v1.28.0.bin"
+        fw_file.write_bytes(b"fake firmware")
+
+        # Insert a DB record using POSIX-style path (as Linux/loader would)
+        posix_path = "esp32/ESP32_GENERIC-v1.28.0.bin"
+        Firmware.create(
+            board_id="ESP32_GENERIC",
+            version="v1.28.0",
+            firmware_file=posix_path,
+            port="esp32",
+        )
+
+        # Patch config.firmware_folder to our tmp_path
+        with patch("mpflash.downloaded.config") as mock_config:
+            mock_config.firmware_folder = tmp_path
+            clean_downloaded_firmwares()
+
+        # The DB record should still exist (not deleted)
+        remaining = list(Firmware.select().where(Firmware.firmware_file == posix_path))
+        assert len(remaining) == 1, "DB record with posix path should NOT be removed when file exists on disk"
+    finally:
+        if not database.is_closed():
+            database.close()
+
+
+def test_fetch_firmware_files_stores_posix_path(tmp_path):
+    """Ensure fetch_firmware_files stores firmware_file as POSIX path in DB."""
+    from mpflash.download.from_web import fetch_firmware_files
+
+    fw = Firmware(
+        board_id="ESP32_GENERIC",
+        version="v1.28.0",
+        firmware_file="ESP32_GENERIC-v1.28.0.bin",
+        port="esp32",
+        source="https://example.com/ESP32_GENERIC-v1.28.0.bin",
+    )
+
+    # Mock requests.get to return fake content
+    class FakeResponse:
+        content = b"fake firmware data"
+
+    import requests as real_requests
+
+    with patch.dict("sys.modules", {"requests": real_requests}):
+        with patch("requests.get", return_value=FakeResponse()):
+            results = list(fetch_firmware_files([fw], tmp_path, force=True))
+
+    assert len(results) == 1
+    result_path = results[0].firmware_file
+    # Path must use forward slashes (POSIX), never backslashes
+    assert "\\" not in result_path, f"firmware_file should use POSIX separators, got: {result_path}"
+    assert result_path == "esp32/ESP32_GENERIC-v1.28.0.bin"