Docker Qt6 xcb issue running pytest

AdamG

I have the following Dockerfile

# Use the official Python base image
FROM python:3.11-bullseye

RUN pip install numpy && pip install setuptools

# Copy the debPackages.txt file
COPY debPackages.txt .

# Install Qt6 dependencies
RUN apt-get update && apt-get install $(grep -vE "^\s*#" debPackages.txt  | tr "\n" " ") -y

# Set the working directory in the container
WORKDIR /app

# Copy the requirements.txt file
COPY requirements.txt .

# Upgrade pip
RUN pip install --upgrade pip

# Install the Python dependencies
RUN pip install --no-cache-dir -r requirements.txt

# Copy the project files
COPY . .



# Copy the test files
# COPY ./tests ./tests

ENV PYTHONDONTWRITEBYTECODE=true
ENV QT_DEBUG_PLUGINS=1
# ENV QTPLUGIN.platforms += qoffscreen
ENV DISPLAY=:0.0
ENV QT_QPA_PLATFORM=offscreen
ENV QT_DEBUG_PLUGINS=1
# ENV QT_QPA_PLATFORM=xcb
ENV QT_QPA_PLATFORM_PLUGIN_PATH=/opt/Qt/${QT_VERSION}/gcc_64/plugins
ENV QT_PLUGIN_PATH=/opt/Qt/${QT_VERSION}/gcc_64/plugins
ENV DISPLAY=:1
ENV PYTHONPATH "${PYTHONPATH}:/app"

RUN pip install .

# Expose the port the application runs on
EXPOSE 8000

CMD ["coverage", "run", "-m", "pytest"]

and have been getting the following error running my docker container:

qt.core.plugin.factoryloader: Got keys from plugin meta data QList("gtk3")
qt.core.plugin.factoryloader: checking directory path "/usr/local/bin/platformthemes" ...
qt.core.plugin.factoryloader: checking directory path "/opt/Qt//gcc_64/plugins" ...
qt.core.plugin.factoryloader: checking directory path "/usr/local/lib/python3.11/site-packages/PySide6/Qt/plugins/styles" ...
qt.core.plugin.factoryloader: checking directory path "/usr/local/bin/styles" ...
Qt WebEngine seems to be initialized from a plugin. Please set Qt::AA_ShareOpenGLContexts using QCoreApplication::setAttribute and QSGRendererInterface::OpenGLRhi using QQuickWindow::setGraphicsApi before constructing QGuiApplication.
qt.core.plugin.factoryloader: checking directory path "/usr/local/lib/python3.11/site-packages/PySide6/Qt/plugins/accessiblebridge" ...
qt.core.plugin.factoryloader: checking directory path "/usr/local/bin/accessiblebridge" ...
WebEngineContext is used before QtWebEngineQuick::initialize() or OpenGL context creation failed.
[1:1:0922/220421.558779:ERROR:zygote_host_impl_linux.cc(100)] Running as root without --no-sandbox is not supported. See https://crbug.com/638180.
"/usr/local/lib/python3.11/site-packages/PySide6/Qt/plugins/platforms/libqoffscreen.so" unloaded library 
make: *** [Makefile:27: test] Error 1

If I take out RUN pip install ., the error won't show up, but the unit tests fail because they can't find the project build. If I replace offscreen with xcb then I get a different error. I've researched this extensively but can't find an answer.

Thank you for any help you can provide.

EDIT:

I just discovered it is an issue specifically with one unit test file in particular. The test is

import pytest
from PySide6.QtWidgets import QApplication
from sys import argv
import sys
from PySide6.QtCore import QUrl

class TestMerlotBrowser:
    @pytest.fixture(autouse=True)
    def setup_method(self, mocker):
        if not QApplication.instance():
            testApp = QApplication(argv)
        else:
            testApp = QApplication.instance()

        with mocker.patch("backend.merlotLogger") as mockLogger, mocker.patch("sql.merlotDB") as mockDB, mocker.patch("backend.persistantProcs") as mockProcs, mocker.patch("attributes.menu") as mockMenu, mocker.patch("PySide6.QtWidgets.QMainWindow.setMenuBar") as mockSetMenuBar:
            from merlot.merlot import Browser
            self.brows = Browser()

    def testBrowser(self):
        assert self.brows.procs.runProcs.call_count == 1
        
    def test_go_to_URL(self):
        testURL = QUrl("www.duckduckgo.com")
        self.brows.go_to_URL(testURL)
        self.brows.db.insertRecord.assert_called_with("https:www.duckduckgo.com")

where Browser is a class Browser(QMainWindow): object. If I remove this test file, the other unit tests run perfectly fine.

AdamG

It turned out the error I needed to research specifically was ERROR:zygote_host_impl_linux.cc(100). I found a solution here:

https://stackoverflow.com/questions/62284578/docker-errorzygote-host-impl-linux-cc89-running-as-root-without-no-sandb

And the new Dockerfile is

# Use the official Python base image
FROM python:3.11-bullseye

RUN pip install numpy && pip install setuptools

# Copy the debPackages.txt file
COPY debPackages.txt .

# Install Qt6 dependencies
RUN apt-get update && apt-get install $(grep -vE "^\s*#" debPackages.txt  | tr "\n" " ") -y

# Set the working directory in the container
WORKDIR /app

# Copy the requirements.txt file
COPY requirements.txt .

# Upgrade pip
RUN pip install --upgrade pip

# Install the Python dependencies
RUN pip install --no-cache-dir -r requirements.txt

# Copy the project files
COPY . .


ENV PYTHONDONTWRITEBYTECODE=true

# Export QT specific settings
ENV QT_DEBUG_PLUGINS=1
ENV QT_QPA_PLATFORM=offscreen
ENV QTWEBENGINE_DISABLE_SANDBOX=1


RUN pip install .

# Expose the port the application runs on
EXPOSE 8000

CMD ["coverage", "run", "-m", "pytest"]

so adding ENV QTWEBENGINE_DISABLE_SANDBOX=1 fixed everything.