Removed duplicate dependencies of examples in the top level workspace (#407)

This PR adds `rust_workspace` which is meant to define transitive dependencies as well as cleans up some duplicate files that were in the root of the project but only used by examples.

## Updated documentation
Note the updated documentation in [docs/index.md](https://github.com/UebelAndre/rules_rust/blob/workspace-structure/docs/index.md)

## Added `bazel_skylib` to `rust_repositories`
It appears there are some uses of `bazel_skylib` within these rules but there aren't really any guarantees that that repository is available. This may be my fault with the changes made in #399 to [@io_bazel_rules_rust//rust/platform:platform.bzl](https://github.com/bazelbuild/rules_rust/blob/master/rust/platform/platform.bzl#L3) but I feel the `bazel_skylib` dependency should be conditionally added

## Added `rust_workspace`
I feel this is much nicer on the users's end as it gives them a single place to go to look at dependencies and is nicer on the repo because it means dependencies can more easily updated. I'm not the biggest fan of the name `rust_workspace` so if this was an acceptable concept, I'm happy to take suggestions on what the name should be called.

Author: UebelAndre

WORKSPACE

@@ -1,28 +1,5 @@
 workspace(name = "io_bazel_rules_rust")
 
-load("@bazel_tools//tools/build_defs/repo:git.bzl", "new_git_repository")
-load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
-
-http_archive(
-    name = "bazel_skylib",
-    sha256 = "1c531376ac7e5a180e0237938a2536de0c54d93f5c278634818e0efc952dd56c",
-    urls = [
-        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
-    ],
-)
-
-load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
-
-bazel_skylib_workspace()
-
-new_git_repository(
-    name = "libc",
-    build_file = "@io_bazel_rules_rust//:libc.BUILD",
-    remote = "https://github.com/rust-lang/libc",
-    tag = "0.2.20",
-)
-
 load("@io_bazel_rules_rust//proto:repositories.bzl", "rust_proto_repositories")
 
 rust_proto_repositories()
@@ -35,8 +12,14 @@ load("@io_bazel_rules_rust//wasm_bindgen:repositories.bzl", "rust_wasm_bindgen_r
 
 rust_wasm_bindgen_repositories()
 
+load("@io_bazel_rules_rust//:workspace.bzl", "rust_workspace")
+
+rust_workspace()
+
 # --- end stardoc
 
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
 http_archive(
     name = "bazel_toolchains",
     sha256 = "d8c2f20deb2f6143bac792d210db1a4872102d81529fe0ea3476c1696addd7ff",
@@ -55,10 +38,6 @@ rbe_autoconfig(
     name = "buildkite_config",
 )
 
-load("@io_bazel_rules_rust//:workspace.bzl", "bazel_version")
-
-bazel_version(name = "bazel_version")
-
 # Load all dependencies for examples
 
 local_repository(

docs/index.md

@@ -16,34 +16,25 @@ To use the Rust rules, add the following to your `WORKSPACE` file to add the ext
 ```python
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
-http_archive(
-    name = "bazel_skylib",
-    urls = [
-        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.3/bazel-skylib-1.0.3.tar.gz",
-    ],
-    sha256 = "1c531376ac7e5a180e0237938a2536de0c54d93f5c278634818e0efc952dd56c",
-)
-
-load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
-bazel_skylib_workspace()
-
 http_archive(
     name = "io_bazel_rules_rust",
-    sha256 = "b6da34e057a31b8a85e343c732de4af92a762f804fc36b0baa6c001423a70ebc",
-    strip_prefix = "rules_rust-55f77017a7f5b08e525ebeab6e11d8896a4499d2",
+    sha256 = "9158524bbbdfded6326d00e76d4fb293efbb07d4e4881416210bac221613432f",
+    strip_prefix = "rules_rust-7d9e890c58ca00eacf8dd4a2ba991cfe9c3f44e4",
     urls = [
-        # Master branch as of 2019-10-07
-        "https://github.com/bazelbuild/rules_rust/archive/55f77017a7f5b08e525ebeab6e11d8896a4499d2.tar.gz",
+        # Master branch as of 2020-09-09
+        "https://github.com/bazelbuild/rules_rust/archive/7d9e890c58ca00eacf8dd4a2ba991cfe9c3f44e4.tar.gz",
     ],
 )
 
 load("@io_bazel_rules_rust//rust:repositories.bzl", "rust_repositories")
+
 rust_repositories()
 
-load("@io_bazel_rules_rust//:workspace.bzl", "bazel_version")
-bazel_version(name = "bazel_version")
+load("@io_bazel_rules_rust//:workspace.bzl", "rust_workspace")
+
+rust_workspace()
 ```
+
 The rules are under active development, as such the lastest commit on the master branch should be used. `master` currently requires Bazel >= 0.26.0.
 
 ## Rules
@@ -85,9 +76,11 @@ Currently the most common approach to managing external dependencies is using
 
 ## WebAssembly
 
-To build a `rust_binary` for wasm32-unknown-unknown add the `--platforms=//rust/platform:wasm` flag.
+To build a `rust_binary` for wasm32-unknown-unknown add the `--platforms=@io_bazel_rules_rust//rust/platform:wasm` flag.
 
-    bazel build @examples//hello_world_wasm --platforms=//rust/platform:wasm
+```command
+bazel build @examples//hello_world_wasm --platforms=@io_bazel_rules_rust//rust/platform:wasm
+```
 
 `rust_wasm_bindgen` will automatically transition to the wasm platform and can be used when
 building wasm code for the host target.

examples/examples_deps.bzl

@@ -3,7 +3,7 @@
 load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
 load("@build_bazel_rules_nodejs//:index.bzl", "node_repositories", "npm_install")
 load("@examples//hello_sys:workspace.bzl", "remote_deps")
-load("@io_bazel_rules_rust//:workspace.bzl", "bazel_version")
+load("@io_bazel_rules_rust//:workspace.bzl", "rust_workspace")
 load("@io_bazel_rules_rust//bindgen:repositories.bzl", "rust_bindgen_repositories")
 load("@io_bazel_rules_rust//proto:repositories.bzl", "rust_proto_repositories")
 load("@io_bazel_rules_rust//rust:repositories.bzl", "rust_repositories", "rust_repository_set")
@@ -37,15 +37,15 @@ def deps():
     # Dependencies for the @examples//hello_world_wasm example.
     npm_install(
         name = "npm",
-        package_json = "//:package.json",
-        package_lock_json = "//:package-lock.json",
+        package_json = "@examples//:package.json",
+        package_lock_json = "@examples//:package-lock.json",
     )
 
     rust_bindgen_repositories()
 
     rust_wasm_bindgen_repositories()
 
-    bazel_version(name = "bazel_version")
+    rust_workspace()
 
     remote_deps()
 

examples/examples_repositories.bzl

@@ -14,7 +14,7 @@ def repositories():
     maybe(
         http_archive,
         name = "libc",
-        build_file = "@//:libc.BUILD",
+        build_file = "@examples//:libc.BUILD",
         sha256 = "1ac4c2ac6ed5a8fb9020c166bc63316205f1dc78d4b964ad31f4f21eb73f0c6d",
         strip_prefix = "libc-0.2.20",
         urls = [