Add minimal examples of toolchains in WORKSPACEs

.bazelignore

@@ -0,0 +1 @@
+examples

.github/workflows/workflow.yaml

@@ -6,11 +6,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-10.15]
+        os: [ubuntu-latest, macos-10.15] # TODO: this job does not yet work on more recent macOS (macos-11)
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
-      - uses: cachix/install-nix-action@v14.1
+      - uses: actions/checkout@v2.4.0
+      - uses: cachix/install-nix-action@v16
         with:
           nix_path: nixpkgs=./nixpkgs.nix
       - name: Configure
@@ -27,3 +27,41 @@ jobs:
             set -euo pipefail
             bazel test //...
           '
+  test-examples:
+    name: Build & Test - Examples
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest] # TODO: this job does not yet work on any version of macOS
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2.4.0
+      - uses: cachix/install-nix-action@v16
+        with:
+          nix_path: nixpkgs=./nixpkgs.nix
+      - name: Configure
+        env:
+          BUILDBUDDY_API_KEY: ${{ secrets.BUILDBUDDY_API_KEY }}
+        run: |
+          cat >.bazelrc.local <<EOF
+          common --config=ci
+          build --remote_header=x-buildbuddy-api-key="$BUILDBUDDY_API_KEY"
+          EOF
+      - name: Build & test
+        run: |
+          cd examples/toolchains
+          for dir in *; do
+              cd "$dir"
+              echo
+              echo Running $(head -n1 README.md) with Nix
+              nix-shell --command 'bazel run --config=nix :hello'
+              # TODO: all toolchains should run without Nixpkgs
+              cd ..
+          done
+          for dir in cc go; do
+              cd "$dir"
+              echo
+              echo Running $(head -n1 README.md) without Nix
+              bazel run :hello
+              cd ..
+          done

examples/.gitignore

@@ -0,0 +1 @@
+bazel-*

examples/toolchains/cc/.bazelrc

@@ -0,0 +1 @@
+build:nix --host_platform=@io_tweag_rules_nixpkgs//nixpkgs/platforms:host

examples/toolchains/cc/BUILD

@@ -0,0 +1,6 @@
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "hello",
+    srcs = ["hello.cc"],
+)

examples/toolchains/cc/README.md

@@ -0,0 +1,19 @@
+C++ Toolchain Example
+=====================
+
+This is an example C++ project that uses `rules_cc`.
+
+If the Nix package manager is present in the build environment, this example will use Nix to provide the C++ toolchain. Otherwise, it will use the toolchain provided by `rules_cc` and not rely on Nix at all.
+
+# Usage
+
+To run the example with Nix, issue the following command:
+```
+nix-shell --command 'bazel run --config=nix :hello'
+```
+
+To run the example without Nix, make sure you have Bazel installed, and issue the following command:
+```
+bazel run :hello
+```
+This non-Nix example will look for the C++ toolchain on the PATH.

examples/toolchains/cc/WORKSPACE

@@ -0,0 +1,43 @@
+# Replace with http_archive: https://github.com/tweag/rules_nixpkgs/#setup
+local_repository(
+    name = "io_tweag_rules_nixpkgs",
+    path = "../../../",
+)
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "rules_cc",
+    sha256 = "4dccbfd22c0def164c8f47458bd50e0c7148f3d92002cdb459c2a96a68498241",
+    urls = [
+        "https://github.com/bazelbuild/rules_cc/releases/download/0.0.1/rules_cc-0.0.1.tar.gz",
+    ],
+)
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:repositories.bzl", "rules_nixpkgs_dependencies")
+
+rules_nixpkgs_dependencies()
+
+load(
+    "@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl",
+    "nixpkgs_cc_configure",
+    "nixpkgs_git_repository",
+)
+
+nixpkgs_git_repository(
+    name = "nixpkgs",
+    revision = "21.11",
+    sha256 = "c77bb41cf5dd82f4718fa789d49363f512bb6fa6bc25f8d60902fe2d698ed7cc",
+)
+
+nixpkgs_cc_configure(
+    name = "nixpkgs_config_cc",
+    fail_not_supported = False,
+    repository = "@nixpkgs",
+)
+
+load("@rules_cc//cc:repositories.bzl", "rules_cc_dependencies", "rules_cc_toolchains")
+
+rules_cc_dependencies()
+
+rules_cc_toolchains()

examples/toolchains/cc/hello.cc

@@ -0,0 +1,6 @@
+#include <iostream>
+
+int main()
+{
+	std::cout << "Hello world!\n";
+}

examples/toolchains/cc/shell.nix

@@ -0,0 +1,6 @@
+{ pkgs ? import (builtins.fetchTarball {
+  url = "https://github.com/NixOS/nixpkgs/archive/21.11.tar.gz";
+  sha256 = "162dywda2dvfj1248afxc45kcrg83appjd0nmdb541hl7rnncf02";
+}) { } }:
+
+pkgs.mkShell { nativeBuildInputs = [ pkgs.bazel_4 ]; }

examples/toolchains/cc_with_deps/.bazelrc

@@ -0,0 +1 @@
+build:nix --host_platform=@io_tweag_rules_nixpkgs//nixpkgs/platforms:host

examples/toolchains/cc_with_deps/BUILD

@@ -0,0 +1,10 @@
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "hello",
+    srcs = ["hello.cc"],
+    deps = [
+        "@boost.dev//:boost",
+        "@zlib.dev//:zlib",
+    ],
+)

examples/toolchains/cc_with_deps/README.md

@@ -0,0 +1,13 @@
+C++ With Dependencies Toolchain Example
+=======================================
+
+This is an example C++ project with dependencies that uses `rules_cc`.
+
+This example uses the Nix package manager to provide C++ dependencies, and as such only works with Nix installed. Demonstrating other methods of providing C++ dependencies is out of scope of this example.
+
+# Usage
+
+To run the example with Nix, issue the following command:
+```
+nix-shell --command 'bazel run --config=nix :hello'
+```

examples/toolchains/cc_with_deps/WORKSPACE

@@ -0,0 +1,81 @@
+# Replace with http_archive: https://github.com/tweag/rules_nixpkgs/#setup
+local_repository(
+    name = "io_tweag_rules_nixpkgs",
+    path = "../../../",
+)
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:repositories.bzl", "rules_nixpkgs_dependencies")
+
+rules_nixpkgs_dependencies()
+
+load(
+    "@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl",
+    "nixpkgs_cc_configure",
+    "nixpkgs_git_repository",
+)
+
+nixpkgs_git_repository(
+    name = "nixpkgs",
+    revision = "21.11",
+    sha256 = "c77bb41cf5dd82f4718fa789d49363f512bb6fa6bc25f8d60902fe2d698ed7cc",
+)
+
+nixpkgs_cc_configure(
+    name = "nixpkgs_config_cc",
+    fail_not_supported = False,
+    repository = "@nixpkgs",
+)
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl", "nixpkgs_package")
+
+nixpkgs_package(
+    name = "boost",
+    attribute_path = "boost175",
+    repository = "@nixpkgs",
+)
+
+nixpkgs_package(
+    name = "boost.dev",
+    attribute_path = "boost175.dev",
+    build_file_content = """\
+load("@rules_cc//cc:defs.bzl", "cc_library")
+filegroup(
+    name = "include",
+    srcs = glob(["include/**/*.h", "include/**/*.hpp"]),
+    visibility = ["//visibility:public"],
+)
+cc_library(
+    name = "boost",
+    srcs = ["@boost//:lib"],
+    hdrs = [":include"],
+    strip_include_prefix = "include",
+    visibility = ["//visibility:public"],
+)
+""",
+    repository = "@nixpkgs",
+)
+
+nixpkgs_package(
+    name = "zlib",
+    repository = "@nixpkgs",
+)
+
+nixpkgs_package(
+    name = "zlib.dev",
+    build_file_content = """\
+load("@rules_cc//cc:defs.bzl", "cc_library")
+filegroup(
+    name = "include",
+    srcs = glob(["include/**/*.h"]),
+    visibility = ["//visibility:public"],
+)
+cc_library(
+    name = "zlib",
+    srcs = ["@zlib//:lib"],
+    hdrs = [":include"],
+    strip_include_prefix = "include",
+    visibility = ["//visibility:public"],
+)
+""",
+    repository = "@nixpkgs",
+)

examples/toolchains/cc_with_deps/hello.cc

@@ -0,0 +1,8 @@
+#include <iostream>
+#include <boost/filesystem/operations.hpp>
+#include <zlib.h>
+
+int main()
+{
+	std::cout << "Hello world!\n";
+}

examples/toolchains/cc_with_deps/shell.nix

@@ -0,0 +1,6 @@
+{ pkgs ? import (builtins.fetchTarball {
+  url = "https://github.com/NixOS/nixpkgs/archive/21.11.tar.gz";
+  sha256 = "162dywda2dvfj1248afxc45kcrg83appjd0nmdb541hl7rnncf02";
+}) { } }:
+
+pkgs.mkShell { nativeBuildInputs = [ pkgs.bazel_4 ]; }

examples/toolchains/go/.bazelrc

@@ -0,0 +1 @@
+build:nix --host_platform=@io_tweag_rules_nixpkgs//nixpkgs/platforms:host

examples/toolchains/go/BUILD

@@ -0,0 +1,6 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary")
+
+go_binary(
+    name = "hello",
+    srcs = ["hello.go"],
+)

examples/toolchains/go/README.md

@@ -0,0 +1,18 @@
+Go Toolchain Example
+====================
+
+This is an example Go project that uses `rules_go`.
+
+If the Nix package manager is present in the build environment, this example will use Nix to provide the Go toolchain. Otherwise, it will use the toolchain provided by `rules_go` and not rely on Nix at all.
+
+# Usage
+
+To run the example with Nix, issue the following command:
+```
+nix-shell --command 'bazel run --config=nix :hello'
+```
+
+To run the example without Nix, make sure you have Bazel installed, and issue the following command:
+```
+bazel run :hello
+```

examples/toolchains/go/WORKSPACE

@@ -0,0 +1,46 @@
+# Replace with http_archive: https://github.com/tweag/rules_nixpkgs/#setup
+local_repository(
+    name = "io_tweag_rules_nixpkgs",
+    path = "../../../",
+)
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "io_bazel_rules_go",
+    sha256 = "2b1641428dff9018f9e85c0384f03ec6c10660d935b750e3fa1492a281a53b0f",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.29.0/rules_go-v0.29.0.zip",
+        "https://github.com/bazelbuild/rules_go/releases/download/v0.29.0/rules_go-v0.29.0.zip",
+    ],
+)
+
+load("@io_bazel_rules_go//go:deps.bzl", "go_rules_dependencies")
+
+go_rules_dependencies()
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:repositories.bzl", "rules_nixpkgs_dependencies")
+
+rules_nixpkgs_dependencies()
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl", "nixpkgs_git_repository")
+
+nixpkgs_git_repository(
+    name = "nixpkgs",
+    revision = "21.11",
+    sha256 = "c77bb41cf5dd82f4718fa789d49363f512bb6fa6bc25f8d60902fe2d698ed7cc",
+)
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:toolchains/go.bzl", "nixpkgs_go_configure")
+
+nixpkgs_go_configure(
+    fail_not_supported = False,
+    repository = "@nixpkgs",
+    sdk_name = "nix_go",
+)
+
+load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
+
+go_rules_dependencies()
+
+go_register_toolchains(version = "1.17.1")

examples/toolchains/go/hello.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+    fmt.Println("Hello world!")
+}

examples/toolchains/go/shell.nix

@@ -0,0 +1,6 @@
+{ pkgs ? import (builtins.fetchTarball {
+  url = "https://github.com/NixOS/nixpkgs/archive/21.11.tar.gz";
+  sha256 = "162dywda2dvfj1248afxc45kcrg83appjd0nmdb541hl7rnncf02";
+}) { } }:
+
+pkgs.mkShell { nativeBuildInputs = [ pkgs.bazel_4 ]; }

examples/toolchains/python/.bazelrc

@@ -0,0 +1 @@
+build:nix --host_platform=@io_tweag_rules_nixpkgs//nixpkgs/platforms:host

examples/toolchains/python/BUILD

@@ -0,0 +1,5 @@
+py_binary(
+    name = "hello",
+    srcs = ["hello.py"],
+    main = "hello.py",
+)

examples/toolchains/python/README.md

@@ -0,0 +1,15 @@
+Python Toolchain Example
+========================
+
+This is an example Python project with modules that uses `rules_python`.
+
+This example uses the Nix package manager to provide Python packages, and as such only works with Nix installed. Demonstrating other methods of providing Python packages is out of scope of this example.
+
+# Usage
+
+To run the example with Nix, issue the following command:
+```
+nix-shell --command 'bazel run --config=nix :hello'
+```
+
+To specify Python version or modules, change the `python3_attribute_path` parameter in the `nixpkgs_python_configure` call in the `WORKSPACE` file.