add macOS unittest to GHA

.github/unittest.sh

@@ -7,6 +7,32 @@ CONDA_PATH=$(which conda)
 eval "$(${CONDA_PATH} shell.bash hook)"
 conda config --set channel_priority strict
 
+# Setup the OS_TYPE environment variable that should be used for conditions involving the OS below.
+case $(uname) in
+  Linux)
+    OS_TYPE=linux
+    ;;
+  Darwin)
+    OS_TYPE=macos
+    ;;
+  *)
+    echo "Unknown OS type:" $(uname)
+    exit 1
+    ;;
+esac
+
+echo '::group::Uninstall system JPEG libraries on macOS'
+# The x86 macOS runners, e.g. the GitHub Actions native "macos-12" runner, has some JPEG libraries installed by default
+# that interfere with our build. We uninstall them here and use the one from conda below.
+if [[ "${OS_TYPE}" == "macos" && $(uname -m) == x86_64 ]]; then
+  JPEG_LIBS=$(brew list | grep jpeg)
+  echo $JPEG_LIBS
+  for lib in $JPEG_LIBS; do
+    brew uninstall --ignore-dependencies --force $lib || true
+  done
+fi
+echo '::endgroup::'
+
 echo '::group::Set PyTorch conda channel and wheel index'
 # TODO: Can we maybe have this as environment variable in the job template? For example, `IS_RELEASE`.
 if [[ (${GITHUB_EVENT_NAME} = 'pull_request' && (${GITHUB_BASE_REF} = 'release'*)) || (${GITHUB_REF} = 'refs/heads/release'*) ]]; then

.github/workflows/test-macos.yml

@@ -0,0 +1,37 @@
+name: Unit-tests on macOS
+
+on:
+  pull_request:
+  push:
+    branches:
+      - nightly
+      - main
+      - release/*
+  workflow_dispatch:
+
+jobs:
+  tests:
+    strategy:
+      matrix:
+        python-version:
+          - "3.8"
+          - "3.9"
+          - "3.10"
+          - "3.11"
+        runner: ["macos-12"]
+        include:
+          - python-version: "3.8"
+            runner: macos-m1-12
+      fail-fast: false
+    uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
+    with:
+      repository: pytorch/vision
+      # We need an increased timeout here, since the macos-12 runner is the free one from GH
+      # and needs roughly 2 hours to just run the test suite
+      timeout: 240
+      runner: ${{ matrix.runner }}
+      script: |
+        export PYTHON_VERSION=${{ matrix.python-version }}
+        export GPU_ARCH_TYPE=cpu
+
+        ./.github/unittest.sh

setup.py

@@ -298,6 +298,8 @@ def get_extensions():
     use_jpeg = use_jpeg and jpeg_found
     if use_jpeg:
         print("Building torchvision with JPEG image support")
+        print(f"  libpng include path: {jpeg_include}")
+        print(f"  libpng lib path: {jpeg_lib}")
         image_link_flags.append("jpeg")
         if jpeg_conda:
             image_library += [jpeg_lib]