This change adds a new rule `grpc_web_toolchain` which we will use to
provide the generator/runtime to `closure_grpc_web_library`.
Updates #507
RELNOTES: [bazel] `closure_grpc_web_library` now uses toolchains to
resolve the generator and runtime. To migrate, add the following snipped
to your `WORKSPACE`:
```starlark
load("@com_github_grpc_grpc_web//bazel:repositories.bzl", "grpc_web_toolchains")
grpc_web_toolchains()
```
This change adds a new `import_style` that emits ES6 modules.
For now, this only re-exports the symbols from `import_style=closure`.
In the future, this will no longer require emitting google modules
(`goog.provide`). If protobuf ever adds support for emitting ES6
modules, we will use them instead of the `goog.provided`'d versions
as well.
Note that the Bazel integration is currently broken because of a
limitation in `rules_closure`.
Not suppressing this causes an error for a missing direct dependency
for the generated gRPC-Web library if a service returns a protobuf
message not declared in the same proto_library.
Yannic Bonenberger
Daniel Bader
factuno-db
Max Vorobev