nullvm: don't enable NullVM by default.

.github/workflows/cpp.yml

@@ -117,6 +117,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
+        - name: 'NullVM on Linux/x86_64'
+          engine: 'null'
+          os: ubuntu-20.04
+          arch: x86_64
+          action: test
+          flags: --config=gcc
         - name: 'V8 on Linux/x86_64'
           engine: 'v8'
           repo: 'v8'
@@ -245,6 +251,7 @@ jobs:
         //test/...
 
     - name: Bazel build/test (signed Wasm module)
+      if: ${{ matrix.engine != 'null' }}
       run: >
         ${{ matrix.run_under }}
         bazel ${{ matrix.action }}

BUILD

@@ -1,6 +1,7 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
 load(
     "@proxy_wasm_cpp_host//bazel:select.bzl",
+    "proxy_wasm_select_engine_null",
     "proxy_wasm_select_engine_v8",
     "proxy_wasm_select_engine_wamr",
     "proxy_wasm_select_engine_wasmtime",
@@ -202,8 +203,9 @@ cc_library(
     name = "lib",
     deps = [
         ":base_lib",
-        ":null_lib",
-    ] + proxy_wasm_select_engine_v8(
+    ] + proxy_wasm_select_engine_null(
+        [":null_lib"],
+    ) + proxy_wasm_select_engine_v8(
         [":v8_lib"],
     ) + proxy_wasm_select_engine_wamr(
         [":wamr_lib"],

bazel/BUILD

@@ -1,5 +1,10 @@
 load("@bazel_skylib//lib:selects.bzl", "selects")
 
+config_setting(
+    name = "engine_null",
+    values = {"define": "engine=null"},
+)
+
 config_setting(
     name = "engine_v8",
     values = {"define": "engine=v8"},

bazel/dependencies.bzl

@@ -57,12 +57,14 @@ def proxy_wasm_cpp_host_dependencies():
         },
     )
 
-    # Core dependencies.
-
-    protobuf_deps()
+    # Test dependencies.
 
     wasmsign_fetch_remote_crates()
 
+    # NullVM dependencies.
+
+    protobuf_deps()
+
     # V8 dependencies.
 
     pip_install(

bazel/repositories.bzl

@@ -75,6 +75,16 @@ def proxy_wasm_cpp_host_repositories():
         urls = ["https://github.com/google/boringssl/archive/eaa29f431f71b8121e1da76bcd3ddc2248238ade.tar.gz"],
     )
 
+    maybe(
+        http_archive,
+        name = "proxy_wasm_cpp_sdk",
+        sha256 = "c57de2425b5c61d7f630c5061e319b4557ae1f1c7526e5a51c33dc1299471b08",
+        strip_prefix = "proxy-wasm-cpp-sdk-fd0be8405db25de0264bdb78fae3a82668c03782",
+        urls = ["https://github.com/proxy-wasm/proxy-wasm-cpp-sdk/archive/fd0be8405db25de0264bdb78fae3a82668c03782.tar.gz"],
+    )
+
+    # Test dependencies.
+
     maybe(
         http_archive,
         name = "com_google_googletest",
@@ -83,6 +93,8 @@ def proxy_wasm_cpp_host_repositories():
         urls = ["https://github.com/google/googletest/archive/release-1.10.0.tar.gz"],
     )
 
+    # NullVM dependencies.
+
     maybe(
         http_archive,
         name = "com_google_protobuf",
@@ -91,14 +103,6 @@ def proxy_wasm_cpp_host_repositories():
         url = "https://github.com/protocolbuffers/protobuf/releases/download/v3.17.3/protobuf-all-3.17.3.tar.gz",
     )
 
-    maybe(
-        http_archive,
-        name = "proxy_wasm_cpp_sdk",
-        sha256 = "c57de2425b5c61d7f630c5061e319b4557ae1f1c7526e5a51c33dc1299471b08",
-        strip_prefix = "proxy-wasm-cpp-sdk-fd0be8405db25de0264bdb78fae3a82668c03782",
-        urls = ["https://github.com/proxy-wasm/proxy-wasm-cpp-sdk/archive/fd0be8405db25de0264bdb78fae3a82668c03782.tar.gz"],
-    )
-
     # V8 with dependencies.
 
     maybe(

bazel/select.bzl

@@ -12,6 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+def proxy_wasm_select_engine_null(xs):
+    return select({
+        "@proxy_wasm_cpp_host//bazel:engine_null": xs,
+        "@proxy_wasm_cpp_host//bazel:multiengine": xs,
+        "//conditions:default": [],
+    })
+
 def proxy_wasm_select_engine_v8(xs):
     return select({
         "@proxy_wasm_cpp_host//bazel:engine_v8": xs,

test/BUILD

@@ -1,3 +1,4 @@
+load("@proxy_wasm_cpp_host//bazel:select.bzl", "proxy_wasm_select_engine_null")
 load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test")
 
 licenses(["notice"])  # Apache 2
@@ -6,7 +7,7 @@ package(default_visibility = ["//visibility:public"])
 
 cc_test(
     name = "null_vm_test",
-    srcs = ["null_vm_test.cc"],
+    srcs = proxy_wasm_select_engine_null(["null_vm_test.cc"]),
     linkstatic = 1,
     deps = [
         "//:lib",