container: Do not leave stale temporary dirs

Do not leave stale temporary directories when conversion fails
unexpectedly. Instead, wrap the conversion operation in a context
manager that wipes the temporary dir afterwards.

Fixes #317

dangerzone/isolation_provider/container.py

@@ -2,6 +2,7 @@ import gzip
 import json
 import logging
 import os
+import pathlib
 import pipes
 import platform
 import shutil
@@ -215,6 +216,34 @@ class Container(IsolationProvider):
         document: Document,
         ocr_lang: Optional[str],
         stdout_callback: Optional[Callable] = None,
+    ) -> bool:
+        # Create a temporary directory inside the cache directory for this run. Then,
+        # create some subdirectories for the various stages of the file conversion:
+        #
+        # * pixel: Where the RGB data will be stored
+        # * safe: Where the final PDF file will be stored
+        with tempfile.TemporaryDirectory(dir=get_tmp_dir()) as t:
+            tmp_dir = pathlib.Path(t)
+            pixel_dir = tmp_dir / "pixels"
+            pixel_dir.mkdir()
+            safe_dir = tmp_dir / "safe"
+            safe_dir.mkdir()
+
+            return self._convert_with_tmpdirs(
+                document=document,
+                pixel_dir=pixel_dir,
+                safe_dir=safe_dir,
+                ocr_lang=ocr_lang,
+                stdout_callback=stdout_callback,
+            )
+
+    def _convert_with_tmpdirs(
+        self,
+        document: Document,
+        pixel_dir: pathlib.Path,
+        safe_dir: pathlib.Path,
+        ocr_lang: Optional[str],
+        stdout_callback: Optional[Callable] = None,
     ) -> bool:
         success = False
 
@@ -223,13 +252,6 @@ class Container(IsolationProvider):
         else:
             ocr = "0"
 
-        dz_tmp = get_tmp_dir()
-        tmpdir = tempfile.TemporaryDirectory(dir=dz_tmp)
-        pixel_dir = os.path.join(tmpdir.name, "pixels")
-        safe_dir = os.path.join(tmpdir.name, "safe")
-        os.makedirs(pixel_dir, exist_ok=True)
-        os.makedirs(safe_dir, exist_ok=True)
-
         # Convert document to pixels
         command = [
             "/usr/bin/python3",
@@ -284,9 +306,6 @@ class Container(IsolationProvider):
                 # We did it
                 success = True
 
-        # Clean up
-        tmpdir.cleanup()
-
         return success
 
     def get_max_parallel_conversions(self) -> int:

tests/test_cli.py

@@ -150,6 +150,10 @@ class TestCli(TestBase):
                 if tmp_path is not None:
                     os.chdir(cwd)
 
+                if tmp_dir.exists():
+                    stale_files = list(tmp_dir.iterdir())
+                    assert not stale_files
+
         return CLIResult.reclass_click_result(result, args)