ci: install only the OpenCV modules the cv extension uses

`libopencv-dev` is a meta-package that hard-depends on the viz and contrib
modules, pulling VTK, OpenMPI, tesseract and ~220 packages. On a throttled
Azure mirror that ran past 50 minutes (libvtk9 alone: 20 MB in ~10 min).
--no-install-recommends would not have helped, since those are hard Depends.

Install libopencv-{core,imgproc}-dev instead. OpenCVConfig.cmake ships only in
the meta-package, so cpp/tests now prefers OpenCV's CMake package when present
and otherwise locates core/imgproc directly; both paths verified to build and
pass all 121 tests.

Also caps the job at 30 minutes so a stalled download fails with logs rather
than running to the 6 h default.

Author: msluszniak

.github/workflows/ci.yml

@@ -43,6 +43,9 @@ jobs:
   native-tests:
     name: C++ unit tests
     runs-on: ubuntu-latest
+    # Well clear of a cold run (dependency build ~2 min) but far below the 6 h
+    # default, so a stalled download fails with logs instead of hanging.
+    timeout-minutes: 30
     defaults:
       run:
         working-directory: packages/react-native-executorch
@@ -70,9 +73,19 @@ jobs:
         with:
           node-version-file: .nvmrc
 
+      # Only the two OpenCV modules the cv extension uses. The `libopencv-dev`
+      # meta-package hard-depends on the viz and contrib modules, which pull VTK,
+      # OpenMPI and ~220 packages — over 50 minutes on a throttled mirror.
+      # OpenCVConfig.cmake ships only in that meta-package, so cpp/tests
+      # falls back to locating the libraries directly.
       - name: Install build tooling
-        run: sudo apt-get update && sudo apt-get install -y ninja-build libopencv-dev
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            ninja-build libopencv-core-dev libopencv-imgproc-dev
         working-directory: ${{ github.workspace }}
+        env:
+          DEBIAN_FRONTEND: noninteractive
 
       - name: Provision third-party headers
         run: RNET_HEADERS_ONLY=1 node scripts/download-libs.js

packages/react-native-executorch/cpp/tests/CMakeLists.txt

@@ -121,8 +121,44 @@ set(RNE_SOURCES
   "${CPP_DIR}/RnExecutorch.cpp"
   ${CORE_SOURCES} ${MATH_SOURCES} ${NLP_SOURCES} ${SPEECH_SOURCES})
 
+# The cv extension uses only core and imgproc. Prefer OpenCV's CMake package
+# when it is installed (Homebrew, or a full distro OpenCV), but fall back to
+# locating the two libraries directly: on Debian/Ubuntu OpenCVConfig.cmake ships
+# only in the `libopencv-dev` meta-package, which hard-depends on the viz and
+# contrib modules and so drags in VTK, OpenMPI and ~220 packages. The fallback
+# lets CI install just libopencv-{core,imgproc}-dev instead.
+function(rne_find_opencv)
+  add_library(rne_opencv INTERFACE)
+
+  find_package(OpenCV QUIET COMPONENTS core imgproc)
+  if(OpenCV_FOUND)
+    message(STATUS "OpenCV: using CMake package ${OpenCV_VERSION}")
+    target_include_directories(rne_opencv INTERFACE ${OpenCV_INCLUDE_DIRS})
+    target_link_libraries(rne_opencv INTERFACE ${OpenCV_LIBS})
+    return()
+  endif()
+
+  find_path(OPENCV_INCLUDE_DIR
+    NAMES opencv2/core.hpp
+    PATH_SUFFIXES opencv4)
+  find_library(OPENCV_CORE_LIB NAMES opencv_core)
+  find_library(OPENCV_IMGPROC_LIB NAMES opencv_imgproc)
+
+  if(NOT OPENCV_INCLUDE_DIR OR NOT OPENCV_CORE_LIB OR NOT OPENCV_IMGPROC_LIB)
+    message(FATAL_ERROR
+      "OpenCV (core + imgproc) not found. Install it with:\n"
+      "  brew install opencv\n"
+      "  apt-get install libopencv-core-dev libopencv-imgproc-dev\n"
+      "or configure with -DRNE_TESTS_ENABLE_OPENCV=OFF to skip the cv suite.")
+  endif()
+
+  message(STATUS "OpenCV: using ${OPENCV_CORE_LIB}")
+  target_include_directories(rne_opencv INTERFACE "${OPENCV_INCLUDE_DIR}")
+  target_link_libraries(rne_opencv INTERFACE "${OPENCV_CORE_LIB}" "${OPENCV_IMGPROC_LIB}")
+endfunction()
+
 if(RNE_TESTS_ENABLE_OPENCV)
-  find_package(OpenCV REQUIRED COMPONENTS core imgproc)
+  rne_find_opencv()
   list(APPEND RNE_SOURCES ${OPENCV_SOURCES})
 endif()
 
@@ -146,7 +182,7 @@ endif()
 
 if(RNE_TESTS_ENABLE_OPENCV)
   target_compile_definitions(rne_under_test PUBLIC RNE_ENABLE_OPENCV)
-  target_link_libraries(rne_under_test PUBLIC ${OpenCV_LIBS})
+  target_link_libraries(rne_under_test PUBLIC rne_opencv)
 endif()
 
 # --- Test support -----------------------------------------------------------

packages/react-native-executorch/cpp/tests/README.md

@@ -65,9 +65,21 @@ scripts/run-native-tests.sh
 scripts/run-native-tests.sh -R MathOpsTest   # extra args go to ctest
 ```
 
-Requires `cmake`, `ninja` and — for the `cv` suite — OpenCV
-(`brew install opencv` / `apt-get install libopencv-dev`). Without OpenCV, run
-with `RNE_TESTS_ENABLE_OPENCV=OFF` to skip that suite.
+Requires `cmake`, `ninja` and — for the `cv` suite — OpenCV's core and imgproc
+modules:
+
+```bash
+brew install opencv                                          # macOS
+apt-get install libopencv-core-dev libopencv-imgproc-dev     # Debian/Ubuntu
+```
+
+Without OpenCV, run with `RNE_TESTS_ENABLE_OPENCV=OFF` to skip that suite.
+
+Note the deliberately narrow apt packages. `libopencv-dev` is a meta-package
+that hard-depends on the viz and contrib modules, so it drags in VTK, OpenMPI
+and ~220 packages — it took over 50 minutes on a throttled CI mirror. Since
+`OpenCVConfig.cmake` ships only in that meta-package, the build prefers OpenCV's
+CMake package when present and otherwise locates the two libraries directly.
 
 ## Keeping the pins honest