feat(internal/librarian): add skeleton for release tag-and-release (#1701)

Also added the one new flag we will need for this command.

Updates: #1009

Author: codyoss

internal/config/config.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"os"
 	"os/user"
+	"regexp"
 	"strings"
 )
 
@@ -49,6 +50,11 @@ const (
 	ReleaseInitRequest = "release-init-request.json"
 )
 
+var (
+	// pullRequestRegexp is regular expression that describes a uri of a pull request.
+	pullRequestRegexp = regexp.MustCompile(`^https://github\.com/([a-zA-Z0-9-._]+)/([a-zA-Z0-9-._]+)/pull/([0-9]+)$`)
+)
+
 // Config holds all configuration values parsed from flags or environment
 // variables. When adding members to this struct, please keep them in
 // alphabetical order.
@@ -130,6 +136,14 @@ type Config struct {
 	// Requires the --library flag to be specified.
 	LibraryVersion string
 
+	// PullRequest to target and operate one in the context of a release.
+	//
+	// The pull request should be in the format `https://github.com/{owner}/{repo}/pull/{number}`.
+	// Setting this field for `tag-and-release` means librarian will only attempt
+	// to process this exact pull request and not search for other pull requests
+	// that may be ready for tagging and releasing.
+	PullRequest string
+
 	// Push determines whether to push changes to GitHub. It is used in
 	// all commands that create commits in a language repository:
 	// configure and update-apis.
@@ -222,6 +236,13 @@ func (c *Config) IsValid() (bool, error) {
 		return false, errors.New("specified library version without library id")
 	}
 
+	if c.PullRequest != "" {
+		matched := pullRequestRegexp.MatchString(c.PullRequest)
+		if !matched {
+			return false, errors.New("pull request URL is not valid")
+		}
+	}
+
 	if _, err := validateHostMount(c.HostMount, ""); err != nil {
 		return false, err
 	}

internal/config/config_test.go

@@ -8,7 +8,7 @@
 //
 // 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.
+// 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.
 
@@ -156,6 +156,12 @@ func TestIsValid(t *testing.T) {
 				Library:     "library-id",
 			},
 		},
+		{
+			name: "Valid config - valid pull request",
+			cfg: Config{
+				PullRequest: "https://github.com/owner/repo/pull/123",
+			},
+		},
 		{
 			name: "Invalid config - Push true, token missing",
 			cfg: Config{
@@ -202,6 +208,14 @@ func TestIsValid(t *testing.T) {
 			wantErr:    true,
 			wantErrMsg: "unable to parse host mount",
 		},
+		{
+			name: "Invalid config - invalid pull request url",
+			cfg: Config{
+				PullRequest: "https://github.com/owner/repo/issues/123",
+			},
+			wantErr:    true,
+			wantErrMsg: "pull request URL is not valid",
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			gotValid, err := test.cfg.IsValid()

internal/librarian/flags.go

@@ -58,3 +58,7 @@ func addFlagRepo(fs *flag.FlagSet, cfg *config.Config) {
 func addFlagWorkRoot(fs *flag.FlagSet, cfg *config.Config) {
 	fs.StringVar(&cfg.WorkRoot, "output", "", "Working directory root. When this is not specified, a working directory will be created in /tmp.")
 }
+
+func addFlagPR(fs *flag.FlagSet, cfg *config.Config) {
+	fs.StringVar(&cfg.PullRequest, "pr", "", "a pull request to operate on. It should be in the format of a uri https://github.com/{owner}/{repo}/pull/{number}. If not specified, will search for all merged pull requests with the label `release:pending` in the last 30 days.")
+}

internal/librarian/librarian.go

@@ -40,6 +40,7 @@ func init() {
 	CmdLibrarian.Init()
 	CmdLibrarian.Commands = append(CmdLibrarian.Commands,
 		cmdGenerate,
+		cmdRelease,
 		cmdVersion,
 	)
 }

internal/librarian/release.go

@@ -0,0 +1,33 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//	https://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 librarian
+
+import (
+	"github.com/googleapis/librarian/internal/cli"
+)
+
+// cmdRelease is the command for the `release` subcommand.
+var cmdRelease = &cli.Command{
+	Short:     "release manages releases of libraries.",
+	UsageLine: "librarian release <command> [arguments]",
+	Long:      "Manages releases of libraries.",
+}
+
+func init() {
+	cmdRelease.Init()
+	CmdLibrarian.Commands = append(CmdLibrarian.Commands,
+		cmdTagAndRelease,
+	)
+}

internal/librarian/tag_and_release.go

@@ -0,0 +1,63 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//	https://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 librarian
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/googleapis/librarian/internal/cli"
+	"github.com/googleapis/librarian/internal/config"
+)
+
+// cmdTagAndRelease is the command for the `release tag-and-release` subcommand.
+var cmdTagAndRelease = &cli.Command{
+	Short:     "release tag-and-release tags and creates a GitHub release for a merged pull request.",
+	UsageLine: "librarian release tag-and-release [arguments]",
+	Long:      "Tags and creates a GitHub release for a merged pull request.",
+	Run: func(ctx context.Context, cfg *config.Config) error {
+		runner, err := newTagAndReleaseRunner(cfg)
+		if err != nil {
+			return err
+		}
+		return runner.run(ctx)
+	},
+}
+
+func init() {
+	cmdTagAndRelease.Init()
+	fs := cmdTagAndRelease.Flags
+	cfg := cmdGenerate.Config
+
+	addFlagRepo(fs, cfg)
+	addFlagPR(fs, cfg)
+}
+
+type tagAndReleaseRunner struct {
+	cfg *config.Config
+}
+
+func newTagAndReleaseRunner(cfg *config.Config) (*tagAndReleaseRunner, error) {
+	if cfg.GitHubToken == "" {
+		return nil, fmt.Errorf("`LIBRARIAN_GITHUB_TOKEN` must be set")
+	}
+	return &tagAndReleaseRunner{
+		cfg: cfg,
+	}, nil
+}
+
+func (r *tagAndReleaseRunner) run(ctx context.Context) error {
+	return nil
+}

internal/librarian/tag_and_release_test.go

@@ -0,0 +1,54 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//	https://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 librarian
+
+import (
+	"testing"
+
+	"github.com/googleapis/librarian/internal/config"
+)
+
+func TestNewTagAndReleaseRunner(t *testing.T) {
+	testcases := []struct {
+		name    string
+		cfg     *config.Config
+		wantErr bool
+	}{
+		{
+			name: "valid config",
+			cfg: &config.Config{
+				GitHubToken: "some-token",
+			},
+			wantErr: false,
+		},
+		{
+			name:    "missing github token",
+			cfg:     &config.Config{},
+			wantErr: true,
+		},
+	}
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			r, err := newTagAndReleaseRunner(tc.cfg)
+			if (err != nil) != tc.wantErr {
+				t.Errorf("newTagAndReleaseRunner() error = %v, wantErr %v", err, tc.wantErr)
+				return
+			}
+			if !tc.wantErr && r == nil {
+				t.Errorf("newTagAndReleaseRunner() got nil runner, want non-nil")
+			}
+		})
+	}
+}