Make Dummy isolation provider more realistic

Make the Dummy isolation provider follow the rest of the isolation
providers and perform the second part of the conversion on the host. The
first part of the conversion is just a dummy script that reads a file
from stdin and prints pixels to stdout.

dangerzone/isolation_provider/dummy.py

@@ -1,18 +1,25 @@
 import logging
-import os
-import shutil
 import subprocess
 import sys
-import time
-from typing import Callable, Optional
 
+from ..conversion.common import DangerzoneConverter
 from ..document import Document
-from ..util import get_resource_path
 from .base import IsolationProvider, terminate_process_group
 
 log = logging.getLogger(__name__)
 
 
+def dummy_script() -> None:
+    sys.stdin.buffer.read()
+    pages = 2
+    width = height = 9
+    DangerzoneConverter._write_int(pages)
+    for page in range(pages):
+        DangerzoneConverter._write_int(width)
+        DangerzoneConverter._write_int(height)
+        DangerzoneConverter._write_bytes(width * height * 3 * b"A")
+
+
 class Dummy(IsolationProvider):
     """Dummy Isolation Provider (FOR TESTING ONLY)
 
@@ -32,51 +39,15 @@ class Dummy(IsolationProvider):
     def install(self) -> bool:
         return True
 
-    def convert(
-        self,
-        document: Document,
-        ocr_lang: Optional[str],
-        progress_callback: Optional[Callable] = None,
-    ) -> None:
-        self.progress_callback = None
-        log.debug("Dummy converter started:")
-        log.debug(
-            f"  - document: {os.path.basename(document.input_filename)} ({document.id})"
-        )
-        log.debug(f"  - ocr     : {ocr_lang}")
-        log.debug("\n(simulating conversion)")
-        success = True
-        progress = [
-            [False, "Converting to PDF using GraphicsMagick", 0.0],
-            [False, "Separating document into pages", 3.0],
-            [False, "Converting page 1/1 to pixels", 5.0],
-            [False, "Converted document to pixels", 50.0],
-            [False, "Converting page 1/1 from pixels to PDF", 50.0],
-            [False, "Merging 1 pages into a single PDF", 95.0],
-            [False, "Compressing PDF", 97.0],
-            [False, "Safe PDF created", 100.0],
-        ]
-        for error, text, percentage in progress:
-            self.print_progress(document, error, text, percentage)  # type: ignore [arg-type]
-            if error:
-                success = False
-        if success:
-            shutil.copy(
-                get_resource_path("dummy_document.pdf"), document.output_filename
-            )
-        document.mark_as_safe()
-        if document.archive_after_conversion:
-            document.archive()
-
-    def pixels_to_pdf(
-        self, document: Document, tempdir: str, ocr_lang: Optional[str]
-    ) -> None:
-        pass
-
     def start_doc_to_pixels_proc(self, document: Document) -> subprocess.Popen:
-        dummy_cmd = ["python3", "-c", "print('The cake is a lie')"]
+        cmd = [
+            sys.executable,
+            "-c",
+            "from dangerzone.isolation_provider.dummy import dummy_script;"
+            " dummy_script()",
+        ]
         return subprocess.Popen(
-            dummy_cmd,
+            cmd,
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
             stderr=self.proc_stderr,

tests/isolation_provider/test_dummy.py

@@ -1,11 +1,9 @@
 import os
-import subprocess
 
 import pytest
 from pytest_mock import MockerFixture
 
 from dangerzone.conversion import errors
-from dangerzone.document import Document
 from dangerzone.isolation_provider.base import IsolationProvider
 from dangerzone.isolation_provider.dummy import Dummy
 
@@ -16,24 +14,6 @@ if not os.environ.get("DUMMY_CONVERSION", False):
     pytest.skip("Dummy conversion is not enabled", allow_module_level=True)
 
 
-class DummyWait(Dummy):
-    """Dummy isolation provider that spawns a blocking process."""
-
-    def start_doc_to_pixels_proc(self, document: Document) -> subprocess.Popen:
-        return subprocess.Popen(
-            ["python3"],
-            stdin=subprocess.PIPE,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-            start_new_session=True,
-        )
-
-
-@pytest.fixture
-def provider_wait() -> DummyWait:
-    return DummyWait()
-
-
 @pytest.fixture
 def provider() -> Dummy:
     return Dummy()
@@ -42,21 +22,12 @@ def provider() -> Dummy:
 class TestDummyTermination(IsolationProviderTermination):
     def test_failed(
         self,
-        provider_wait: IsolationProvider,
+        provider: IsolationProvider,
         mocker: MockerFixture,
     ) -> None:
         mocker.patch.object(
-            provider_wait,
+            provider,
             "get_proc_exception",
             return_value=errors.DocFormatUnsupported(),
         )
-        super().test_failed(provider_wait, mocker)
+        super().test_failed(provider, mocker)
-
-    def test_linger_unkillable(
-        self,
-        provider_wait: IsolationProvider,
-        mocker: MockerFixture,
-    ) -> None:
-        # We have to spawn a blocking process here, else we can't imitate an
-        # "unkillable" process.
-        super().test_linger_unkillable(provider_wait, mocker)