Add distrib test for CMake FetchContent build

examples/cpp/helloworld/CMakeLists.txt

@@ -63,7 +63,32 @@ if(GRPC_AS_SUBMODULE)
   else()
     set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
   endif()
+elseif(GRPC_FETCHCONTENT)
+  # Another way is to use CMake's FetchContent module to clone gRPC at
+  # configure time. This makes gRPC's source code available to your project,
+  # similar to a git submodule.
+  message(STATUS "Using gRPC via add_subdirectory (FetchContent).")
+  include(FetchContent)
+  FetchContent_Declare(
+    grpc
+    GIT_REPOSITORY https://github.com/grpc/grpc.git
+    # when using gRPC, you will actually set this to an existing tag, such as
+    # v1.25.0, v1.26.0 etc..
+    # For the purpose of testing, we override the tag used to the commit
+    # that's currently under test.
+    GIT_TAG        vGRPC_TAG_VERSION_OF_YOUR_CHOICE)
+  FetchContent_MakeAvailable(grpc)
 
+  # Since FetchContent uses add_subdirectory under the hood, we can use
+  # the grpc targets directly from this build.
+  set(_PROTOBUF_LIBPROTOBUF libprotobuf)
+  set(_PROTOBUF_PROTOC $<TARGET_FILE:protoc>)
+  set(_GRPC_GRPCPP_UNSECURE grpc++_unsecure)
+  if(CMAKE_CROSSCOMPILING)
+    find_program(_GRPC_CPP_PLUGIN_EXECUTABLE grpc_cpp_plugin)
+  else()
+    set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
+  endif()
 else()
   # This branch assumes that gRPC and all its dependencies are already installed
   # on this system, so they can be located by find_package().

test/distrib/cpp/run_distrib_test_cmake_fetchcontent.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -ex
+
+cd "$(dirname "$0")/../../.."
+grpc_dir=$(pwd)
+
+echo "deb http://archive.debian.org/debian jessie-backports main" | tee /etc/apt/sources.list.d/jessie-backports.list
+echo 'Acquire::Check-Valid-Until "false";' > /etc/apt/apt.conf
+sed -i '/deb http:\/\/deb.debian.org\/debian jessie-updates main/d' /etc/apt/sources.list
+apt-get update
+apt-get install -t jessie-backports -y libssl-dev wget
+
+# Install CMake 3.16
+wget -q -O cmake-linux.sh https://github.com/Kitware/CMake/releases/download/v3.16.1/cmake-3.16.1-Linux-x86_64.sh
+sh cmake-linux.sh -- --skip-license --prefix=/usr
+rm cmake-linux.sh
+
+# Build helloworld example.
+# This uses CMake's FetchContent module to download gRPC and its dependencies
+# and add it to the helloworld project as a subdirectory.
+mkdir -p "examples/cpp/helloworld/cmake/build"
+pushd "examples/cpp/helloworld/cmake/build"
+# We set FETCHCONTENT_SOURCE_DIR_GRPC to use the existing gRPC checkout
+# rather than cloning a release.
+cmake \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DgRPC_BUILD_TESTS=OFF \
+  -DgRPC_SSL_PROVIDER=package \
+  -DGRPC_FETCHCONTENT=ON \
+  -DFETCHCONTENT_SOURCE_DIR_GRPC="$grpc_dir" \
+  ../..
+make -j4
+popd

tools/run_tests/artifacts/distribtest_targets.py

@@ -301,6 +301,7 @@ def targets():
         CppDistribTest('linux', 'x64', 'jessie', 'cmake'),
         CppDistribTest('linux', 'x64', 'jessie', 'cmake_as_externalproject'),
         CppDistribTest('linux', 'x64', 'jessie', 'cmake_as_submodule'),
+        CppDistribTest('linux', 'x64', 'jessie', 'cmake_fetchcontent'),
         CppDistribTest('linux', 'x64', 'jessie', 'cmake_module_install'),
         CppDistribTest('linux', 'x64', 'jessie', 'cmake_pkgconfig'),
         CppDistribTest('linux', 'x64', 'jessie', 'raspberry_pi'),