n-api: add support for abi stable module API

Add support for abi stable module API (N-API) as "Experimental feature".
The goal of this API is to provide a stable Node API for native
module developers. N-API aims to provide ABI compatibility guarantees
across different Node versions and also across different
Node VMs - allowing N-API enabled native modules to just work
across different versions and flavors of Node.js without recompilation.

A more detailed introduction is provided in:
https://github.com/nodejs/node-eps/blob/master/005-ABI-Stable-Module-API.md
and https://github.com/nodejs/abi-stable-node/blob/doc/VM%20Summit.pdf.

The feature, during its experimental state, will be guarded by a runtime
flag "--napi-modules". Only when this flag is added to the command line
will N-API modules along with regular non N-API modules be supported.

The API is defined by the methods in "src/node_api.h" and
"src/node_api_types.h". This is the best
starting point to review the API surface. More documentation will follow.

In addition to the implementation of the API using V8, which is included
in this PR, the API has also been validated against chakracore and that
port is available in
https://github.com/nodejs/abi-stable-node/tree/api-prototype-chakracore-8.x.

The current plan is to provide N-API support in versions 8.X and 6.X
directly. For older versions, such as 4.X or pre N-API versions of 6.X,
we plan to create an external npm module to provide a migration path
that will allow modules targeting older Node.js versions to use the API,
albeit without getting the advantage of not having to recompile.

In addition, we also plan an external npm package with C++ sugar to
simplify the use of the API. The sugar will be in-line only and will
only use the exported N-API methods but is not part of the N-API
itself. The current version is in:
https://github.com/nodejs/node-api.

This PR is a result of work in the abi-stable-node repo:
https://github.com/nodejs/abi-stable-node/tree/doc,
with this PR being the cumulative work on the api-prototype-8.x
branch with the following contributors in alphabetical order:

Author: Arunesh Chandra <arunesh.chandra@microsoft.com>
Author: Gabriel Schulhof <gabriel.schulhof@intel.com>
Author: Hitesh Kanwathirtha <hiteshk@microsoft.com>
Author: Ian Halliday <ianhall@microsoft.com>
Author: Jason Ginchereau <jasongin@microsoft.com>
Author: Michael Dawson <michael_dawson@ca.ibm.com>
Author: Sampson Gao <sampsong@ca.ibm.com>
Author: Taylor Woll <taylor.woll@microsoft.com>
Backport-PR-URL: #19447
PR-URL: #11975
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: jasongin

Makefile

@@ -120,9 +120,10 @@ v8:
 
 test: all
 	$(MAKE) build-addons
+	$(MAKE) build-addons-napi
 	$(MAKE) cctest
 	$(PYTHON) tools/test.py --mode=release -J \
-		doctool inspector known_issues message pseudo-tty parallel sequential addons
+		doctool inspector known_issues message pseudo-tty parallel sequential addons addons-napi
 	$(MAKE) lint
 
 test-parallel: all
@@ -189,6 +190,41 @@ test/addons/.buildstamp: config.gypi \
 # TODO(bnoordhuis) Force rebuild after gyp update.
 build-addons: $(NODE_EXE) test/addons/.buildstamp
 
+ADDONS_NAPI_BINDING_GYPS := \
+	$(filter-out test/addons-napi/??_*/binding.gyp, \
+		$(wildcard test/addons-napi/*/binding.gyp))
+
+ADDONS_NAPI_BINDING_SOURCES := \
+	$(filter-out test/addons-napi/??_*/*.cc, $(wildcard test/addons-napi/*/*.cc)) \
+	$(filter-out test/addons-napi/??_*/*.h, $(wildcard test/addons-napi/*/*.h))
+
+# Implicitly depends on $(NODE_EXE), see the build-addons-napi rule for rationale.
+test/addons-napi/.buildstamp: config.gypi \
+	deps/npm/node_modules/node-gyp/package.json \
+	$(ADDONS_NAPI_BINDING_GYPS) $(ADDONS_NAPI_BINDING_SOURCES) \
+	deps/uv/include/*.h deps/v8/include/*.h \
+	src/node.h src/node_buffer.h src/node_object_wrap.h src/node_version.h \
+	src/node_api.h src/node_api_types.h
+#	Cannot use $(wildcard test/addons-napi/*/) here, it's evaluated before
+#	embedded addons have been generated from the documentation.
+	@for dirname in test/addons-napi/*/; do \
+		printf "\nBuilding addon $$PWD/$$dirname\n" ; \
+		env MAKEFLAGS="-j1" $(NODE) deps/npm/node_modules/node-gyp/bin/node-gyp \
+		        --loglevel=$(LOGLEVEL) rebuild \
+			--python="$(PYTHON)" \
+			--directory="$$PWD/$$dirname" \
+			--nodedir="$$PWD" || exit 1 ; \
+	done
+	touch $@
+
+# .buildstamp and .docbuildstamp need $(NODE_EXE) but cannot depend on it
+# directly because it calls make recursively.  The parent make cannot know
+# if the subprocess touched anything so it pessimistically assumes that
+# .buildstamp and .docbuildstamp are out of date and need a rebuild.
+# Just goes to show that recursive make really is harmful...
+# TODO(bnoordhuis) Force rebuild after gyp or node-gyp update.
+build-addons-napi: $(NODE_EXE) test/addons-napi/.buildstamp
+
 clear-stalled:
 	# Clean up any leftover processes but don't error if found.
 	ps awwx | grep Release/node | grep -v grep | cat
@@ -200,20 +236,22 @@ clear-stalled:
 test-gc: all test/gc/node_modules/weak/build/Release/weakref.node
 	$(PYTHON) tools/test.py --mode=release gc
 
-test-build: | all build-addons
+test-build: | all build-addons build-addons-napi
+
+test-build-addons-napi: all build-addons-napi
 
 test-all: test-build test/gc/node_modules/weak/build/Release/weakref.node
 	$(PYTHON) tools/test.py --mode=debug,release
 
 test-all-valgrind: test-build
 	$(PYTHON) tools/test.py --mode=debug,release --valgrind
 
-CI_NATIVE_SUITES := addons
+CI_NATIVE_SUITES := addons addons-napi
 CI_JS_SUITES := doctool inspector known_issues message parallel pseudo-tty sequential
 
 # Build and test addons without building anything else
 test-ci-native: LOGLEVEL := info
-test-ci-native: | test/addons/.buildstamp
+test-ci-native: | test/addons/.buildstamp test/addons-napi/.buildstamp
 	$(PYTHON) tools/test.py $(PARALLEL_ARGS) -p tap --logfile test.tap \
 		--mode=release --flaky-tests=$(FLAKY_TESTS) \
 		$(TEST_CI_ARGS) $(CI_NATIVE_SUITES)
@@ -231,11 +269,11 @@ test-ci-js: | clear-stalled
 	fi
 
 test-ci: LOGLEVEL := info
-test-ci: | clear-stalled build-addons
+test-ci: | clear-stalled build-addons build-addons-napi
 	out/Release/cctest --gtest_output=tap:cctest.tap
 	$(PYTHON) tools/test.py $(PARALLEL_ARGS) -p tap --logfile test.tap \
 		--mode=release --flaky-tests=$(FLAKY_TESTS) \
-		$(TEST_CI_ARGS) $(CI_JS_SUITES) $(CI_NATIVE_SUITES)
+		$(TEST_CI_ARGS) $(CI_JS_SUITES) addons-napi $(CI_NATIVE_SUITES)
 	# Clean up any leftover processes, error if found.
 	ps awwx | grep Release/node | grep -v grep | cat
 	@PS_OUT=`ps awwx | grep Release/node | grep -v grep | awk '{print $$1}'`; \
@@ -282,7 +320,10 @@ test-npm: $(NODE_EXE)
 test-npm-publish: $(NODE_EXE)
 	npm_package_config_publishtest=true $(NODE) deps/npm/test/run.js
 
-test-addons: test-build
+test-addons-napi: test-build-addons-napi
+	$(PYTHON) tools/test.py --mode=release addons-napi
+
+test-addons: test-build test-addons-napi
 	$(PYTHON) tools/test.py --mode=release addons
 
 test-addons-clean:
@@ -813,6 +854,8 @@ LINT_CPP_FILES = $(filter-out $(LINT_CPP_EXCLUDE), $(wildcard \
 	test/addons/*/*.h \
 	test/cctest/*.cc \
 	test/cctest/*.h \
+	test/addons-napi/*/*.cc \
+	test/addons-napi/*/*.h \
 	tools/icu/*.cc \
 	tools/icu/*.h \
 	))
@@ -857,5 +900,6 @@ endif
         bench-buffer bench-net bench-http bench-fs bench-tls cctest run-ci \
         test-v8 test-v8-intl test-v8-benchmarks test-v8-all v8 lint-ci \
         bench-ci lint-js-ci doc-only $(TARBALL)-headers test-ci test-ci-native \
-        test-ci-js build-ci test-hash-seed clear-stalled
+        test-ci-js build-ci test-hash-seed clear-stalled  test-addons-napi \
+        build-addons-napi
 

doc/api/cli.md

@@ -119,6 +119,14 @@ added: v6.0.0
 
 Silence all process warnings (including deprecations).
 
+### `--napi-modules`
+<!-- YAML
+added: REPLACEME
+-->
+
+Enable loading native modules compiled with the ABI-stable Node.js API (N-API)
+(experimental).
+
 ### `--trace-warnings`
 <!-- YAML
 added: v6.0.0