Buck2 golang example (#355)

- Add an example of RE with Buck2 for a simple golang project.
- See readme for more details.

Author: nlopezgi

buck2/golang/.buckconfig

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+[cells]
+  root = .
+  prelude = prelude
+  toolchains = toolchains
+  none = none
+
+[cell_aliases]
+  config = prelude
+  fbcode = none
+  fbsource = none
+  buck = none
+
+[external_cells]
+  prelude = bundled
+
+[parser]
+  target_platform_detector_spec = target:root//...->prelude//platforms:default
+
+[buck2]
+digest_algorithms = SHA256
+
+[buck2_re_client]
+engine_address       = <CLUSTER_NAME>.cluster.engflow.com
+action_cache_address = <CLUSTER_NAME>.cluster.engflow.com
+cas_address          = <CLUSTER_NAME>.cluster.engflow.com
+http_headers         = x-engflow-auth-method:jwt-v0,x-engflow-auth-token:LONG_JWT_STRING
+
+[build]
+  execution_platforms = root//platforms:remote_platform
+
+[project]
+  ignore = .git

buck2/golang/.buckroot

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+/buck-out

buck2/golang/.gitignore

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+# EngFlow RE + Buck2 Go example
+
+This example demonstrates use of EngFlow RE for a simple Go lang project built with [Buck2](https://github.com/facebook/buck2) using the prelude.
+
+It is based on three existing samples in the Buck2 upstream repo and the EngFlow samples repo:
+
+* Simple go project with prelude - https://github.com/facebook/buck2/tree/main/examples/with_prelude/go
+* Buck2 remote execution integration with EngFlow - https://github.com/facebook/buck2/tree/main/examples/remote_execution/engflow
+* EngFlow go example - https://github.com/EngFlow/example/tree/main/go
+
+### Example structure
+
+In the `platforms` cell we specify:
+* The platform used for remote execution in this project `root//platforms:remote_platform`, which includes the definition of the Docker image used for remote execution, and that defines constraints for targets to run in the remote execution environment. This platform provides an `ExecutionPlatformRegistrationInfo`.
+* The action keys `root//platforms:remote_execution_action_keys`, which provides a default `BuildModeInfo` that is needed for RE of tests to function properly.
+* The platform `image` configured in `platforms/defs.bzl`, notably, uses a different image than other Buck2 samples in this repo. Specifically, it uses a public AWS image that has `go` preinstalled. This is because, unlike Bazel go rules, Buck2 go rules do not include a hermetic go binary.
+
+In the `toolchains` cell we specify:
+
+* The remote go toolchain `root//toolchains:remote_go_toolchain` and remote go bootstrap toolchain `root//toolchains:remote_go_bootstrap_toolchain`, which are compatible with the remote execution environment. These toolchains are configured for `go_arch` set to `amd64` and `go_os` set to `linux`.
+* The remote test execution toolchain, `root//toolchains:remote_test_execution_toolchain`. This toolchain defines platform options in the form of `capabilities`. Critically these include the `container-image`. This toolchain is identical to the one in the `buck2/cpp` sample in this repo.
+
+The `main` cell and `library` cell:
+
+* Contains an copied version of https://github.com/facebook/buck2/tree/main/examples/with_prelude/go that works with Buck2 and RE as configured in this sample project.
+
+To test this cell with RE run (after setting up `.buckconfig` as indicated below):
+
+```
+buck2 test //go/greeting:greeting_test
+```
+
+You can also build the `main` for this sample by running:
+
+```
+buck2 build //go:hello 
+```
+
+### Relevant configs in `.buckconfig`
+
+The EngFlow endpoint and certificate should be configured as the
+following:
+
+```ini
+[buck2_re_client]
+engine_address       = <CLUSTER_NAME>.cluster.engflow.com
+action_cache_address = <CLUSTER_NAME>.cluster.engflow.com
+cas_address          = <CLUSTER_NAME>.cluster.engflow.com
+http_headers         = x-engflow-auth-method:jwt-v0,x-engflow-auth-token:LONG_JWT_STRING
+ ```
+
+To obtain the value of `LONG_JWT_STRING`, log into https://<CLUSTER_NAME>.cluster.engflow.com/gettingstarted and use the value of `x-engflow-auth-token` in section `Method 2: JWT`.

buck2/golang/README.md

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+# Copyright 2022 EngFlow Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+go_binary(
+    name = "hello",
+    srcs = ["main.go"],
+    deps = [
+        "//go/greeting:greeting",
+    ],
+)

buck2/golang/go/BUCK

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+# Copyright 2022 EngFlow Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+go_library(
+    name = "greeting",
+    srcs = glob(["*.go"]),
+    visibility = ["PUBLIC"],
+)
+
+go_test(
+    name = "greeting_test",
+    srcs = glob(["*.go"]),
+    remote_execution_action_key_providers = "//platforms:remote_execution_action_keys",
+)

buck2/golang/go/greeting/BUCK

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+
+package greeting
+
+// Greeting returns a greeting message
+func Greeting() string {
+	return "Hello, world!"
+}

buck2/golang/go/greeting/greeting.go

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+package greeting
+
+import "testing"
+
+func TestHello(t *testing.T) {
+	if Greeting() != "Hello, world!" {
+		t.Errorf("Greeting() = %v, want \"Hello, world!\"", Greeting())
+	}
+}

buck2/golang/go/greeting/greeting_test.go

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+package main
+
+import (
+	"fmt"
+
+	"go/greeting"
+)
+
+func main() {
+	fmt.Println(greeting.Greeting())
+}

buck2/golang/go/main.go

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+# Copyright 2022 EngFlow Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load(":defs.bzl", "platforms")
+load(":defs.bzl", "action_keys")
+
+# This platform configures details of remote execution.
+platforms(
+    name = "remote_platform",
+)
+
+# This action_key provides a default BuildModeInfo that is needed for RE of tests to function properly.
+# The values in `cell` and `mode` can be used, in practice, to create cache silos. Any values can be given to these attributes.
+action_keys(
+    name = "remote_execution_action_keys",
+    cell = "standard",
+    mode = "standard",
+    visibility = ["PUBLIC"],
+)

buck2/golang/platforms/BUCK

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+# Copyright 2022 EngFlow Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This platform is essentially the same as the one provided in https://github.com/facebook/buck2/blob/804d62242214455d51787f7c8c96a1e12c75ec32/examples/remote_execution/engflow/platforms/defs.bzl
+# The main difference is we enable passing CPU and OS constraints and we use the sample EngFlow RE image.
+load("@prelude//:build_mode.bzl", "BuildModeInfo")
+
+def _platforms(ctx):
+    constraints = dict()
+    configuration = ConfigurationInfo(
+        constraints = constraints,
+        values = {},
+    )
+
+    # A bookworm image with go pre-installed.
+    # Unlike Bazel go_toolchain, Buck2 go_toolchain does not include a hermetic go binary.
+    image = "docker://public.ecr.aws/docker/library/golang:1.23.3-bookworm@sha256:3f3b9daa3de608f3e869cd2ff8baf21555cf0fca9fd34251b8f340f9b7c30ec5"
+    name = ctx.label.raw_target()
+    platform = ExecutionPlatformInfo(
+        label = ctx.label.raw_target(),
+        configuration = configuration,
+        executor_config = CommandExecutorConfig(
+            local_enabled = False,
+            remote_enabled = True,
+            use_limited_hybrid = False,
+            remote_execution_properties = {
+                "container-image": image,
+            },
+            remote_execution_use_case = "buck2-default",
+            # TODO: Use output_paths
+            remote_output_paths = "strict",
+        ),
+    )
+
+    return [
+        DefaultInfo(),
+        ExecutionPlatformRegistrationInfo(platforms = [platform]),
+    ]
+
+def _action_keys(ctx):
+    return [
+        DefaultInfo(),
+        BuildModeInfo(cell = ctx.attrs.cell, mode = ctx.attrs.mode),
+    ]
+
+platforms = rule(
+    attrs = {}, 
+    impl = _platforms
+)
+
+action_keys = rule(
+     attrs = {
+        "cell": attrs.string(),
+        "mode": attrs.string(),
+     },
+     impl = _action_keys
+)

buck2/golang/platforms/defs.bzl

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+
+# Copyright 2022 EngFlow Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("defs.bzl", "remote_go_toolchain", "remote_go_bootstrap_toolchain")
+load("@prelude//toolchains:cxx.bzl", "cxx_tools_info_toolchain")
+load("@prelude//toolchains:python.bzl", "system_python_bootstrap_toolchain")
+load("@prelude//toolchains:remote_test_execution.bzl", "remote_test_execution_toolchain")
+load("@prelude//tests:test_toolchain.bzl", "noop_test_toolchain")
+
+# Python toolchain used in scripts that bootstrap other aspects of the Buck2 prelude.
+system_python_bootstrap_toolchain(
+    name = "python_bootstrap",
+    visibility = ["PUBLIC"],
+)
+
+remote_go_bootstrap_toolchain(
+    name = "go_bootstrap",
+    visibility = ["PUBLIC"],
+)
+
+# c++ toolchain required implicitly for py targets.
+cxx_tools_info_toolchain(
+    name = "cxx",
+    visibility = ["PUBLIC"],
+)
+
+remote_go_toolchain(
+    name = "go",
+    visibility = ["PUBLIC"],
+)
+
+# Default toolchain for remote execution of tests.
+# Note it defines a profile with a capability that defines the `container-image` that matches the one defined in //platforms:remote_platform. 
+# Capabilities are passed to the RE service to find workers that match them as Platform options.
+remote_test_execution_toolchain(
+    name = "remote_test_execution",
+    visibility = ["PUBLIC"],
+    default_profile = "cxx_re_toolchain",
+    profiles = {
+        "cxx_re_toolchain": {
+            "use_case": "cxx-testing",
+            "capabilities": {
+                "container-image" : "docker://gcr.io/bazel-public/ubuntu2004-java11@sha256:69a78f121230c6d5cbfe2f4af8ce65481aa3f2acaaaf8e899df335f1ac1b35b5",
+            },
+        }
+    },
+)
+
+# In some cases the execution of test can fail looking for this `noop_test_toolchain`.
+noop_test_toolchain(
+    name = "test",
+    visibility = ["PUBLIC"],
+)