feat(go-lib/version): add Handler and HandlerFor http.Handler

src/libraries/go/lib/pkg/version/BUILD.bazel

@@ -18,6 +18,7 @@ load("@rules_go//go:def.bzl", "go_library", "go_test")
 go_library(
     name = "version",
     srcs = [
+        "handler.go",
         "http.go",
         "version.go",
     ],
@@ -28,6 +29,7 @@ go_library(
 go_test(
     name = "version_test",
     srcs = [
+        "handler_test.go",
         "http_test.go",
         "version_test.go",
     ],

src/libraries/go/lib/pkg/version/handler.go

@@ -0,0 +1,85 @@
+/*
+SPDX-FileCopyrightText: Copyright (c) NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+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.
+*/
+
+package version
+
+import (
+	"encoding/json"
+	"net/http"
+	"runtime/debug"
+)
+
+// Info holds the resolved build metadata returned by the GET /info endpoint.
+type Info struct {
+	Service string `json:"service"`
+	Version string `json:"version"`
+	Commit  string `json:"commit"`
+}
+
+// Handler returns an http.Handler that serves build info as JSON.
+// Service, Version, and Commit are resolved from the package-level ldflags vars
+// (Service, Version, GitHash), with buildinfo used as a fallback for Commit
+// when GitHash is empty.
+func Handler() http.Handler {
+	return HandlerFor(Service, Version, GitHash)
+}
+
+// HandlerFor returns an http.Handler using the provided service, version, and
+// commit values, falling back to buildinfo for commit when commit is empty.
+// Use this for services that maintain their own ldflags vars rather than
+// pointing directly at this package.
+func HandlerFor(service, ver, commit string) http.Handler {
+	info := resolve(service, ver, commit)
+	body, _ := json.Marshal(info)
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(body)
+	})
+}
+
+// resolve builds an Info by combining the given service/ver/commit,
+// falling back to runtime buildinfo for commit when empty.
+func resolve(service, ver, commit string) Info {
+	if commit == "" {
+		commit = commitFromBuildInfo()
+	}
+	if service == "" {
+		service = "unknown"
+	}
+	if ver == "" {
+		ver = "unknown"
+	}
+	if commit == "" {
+		commit = "unknown"
+	}
+	return Info{Service: service, Version: ver, Commit: commit}
+}
+
+// commitFromBuildInfo reads the VCS revision from Go's embedded build info
+// (available when built inside a git repository without -buildvcs=false).
+func commitFromBuildInfo() string {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return ""
+	}
+	for _, s := range info.Settings {
+		if s.Key == "vcs.revision" {
+			return s.Value
+		}
+	}
+	return ""
+}

src/libraries/go/lib/pkg/version/handler_test.go

@@ -0,0 +1,128 @@
+/*
+SPDX-FileCopyrightText: Copyright (c) NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+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.
+*/
+
+package version
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHandlerFor(t *testing.T) {
+	tests := []struct {
+		name        string
+		service     string
+		ver         string
+		commit      string
+		wantService string
+		wantVersion string
+		wantCommit  string
+	}{
+		{
+			name:        "all set",
+			service:     "nvcf-my-service",
+			ver:         "1.2.3",
+			commit:      "abc1234",
+			wantService: "nvcf-my-service",
+			wantVersion: "1.2.3",
+			wantCommit:  "abc1234",
+		},
+		{
+			name:        "empty service falls back to unknown",
+			service:     "",
+			ver:         "1.2.3",
+			commit:      "abc1234",
+			wantService: "unknown",
+			wantVersion: "1.2.3",
+			wantCommit:  "abc1234",
+		},
+		{
+			name:        "empty version falls back to unknown",
+			service:     "nvcf-my-service",
+			ver:         "",
+			commit:      "abc1234",
+			wantService: "nvcf-my-service",
+			wantVersion: "unknown",
+			wantCommit:  "abc1234",
+		},
+		{
+			name:        "empty commit falls back to buildinfo or unknown",
+			service:     "nvcf-my-service",
+			ver:         "1.2.3",
+			commit:      "",
+			wantService: "nvcf-my-service",
+			wantVersion: "1.2.3",
+			// commit will be whatever buildinfo provides in the test binary,
+			// or "unknown" -- just assert it is non-empty string
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			w := httptest.NewRecorder()
+			r := httptest.NewRequest(http.MethodGet, "/info", nil)
+			HandlerFor(tc.service, tc.ver, tc.commit).ServeHTTP(w, r)
+
+			assert.Equal(t, http.StatusOK, w.Code)
+			assert.Equal(t, "application/json", w.Header().Get("Content-Type"))
+
+			var got Info
+			require.NoError(t, json.Unmarshal(w.Body.Bytes(), &got))
+
+			if tc.wantService != "" {
+				assert.Equal(t, tc.wantService, got.Service)
+			}
+			if tc.wantVersion != "" {
+				assert.Equal(t, tc.wantVersion, got.Version)
+			}
+			if tc.wantCommit != "" {
+				assert.Equal(t, tc.wantCommit, got.Commit)
+			}
+			assert.NotEmpty(t, got.Commit)
+		})
+	}
+}
+
+func TestHandler(t *testing.T) {
+	t.Cleanup(func() {
+		Service = ""
+		Version = ""
+		GitHash = ""
+	})
+
+	Service = "nvcf-my-service"
+	Version = "2.0.0"
+	GitHash = "deadbeef"
+
+	w := httptest.NewRecorder()
+	r := httptest.NewRequest(http.MethodGet, "/info", nil)
+	Handler().ServeHTTP(w, r)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, "application/json", w.Header().Get("Content-Type"))
+
+	var got Info
+	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &got))
+	assert.Equal(t, "nvcf-my-service", got.Service)
+	assert.Equal(t, "2.0.0", got.Version)
+	assert.Equal(t, "deadbeef", got.Commit)
+}

src/libraries/go/lib/pkg/version/version.go

@@ -21,6 +21,7 @@ import "strings"
 
 // Following variables are set by CI during compilation.
 var (
+	Service string
 	Version string
 	GitHash string
 	// Dirty is set to "true" if current git working directory has