github-pull-request-make: allow testing command generation

This adds the ability to feed in package and test names via an
environment variable rather than depending on GitHub. It also allows
one to force a bazel build. I found this helpful when debugging a
problem with this command.

Release note: None

pkg/cmd/github-pull-request-make/main.go

@@ -31,6 +31,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -40,9 +41,16 @@ import (
 	"golang.org/x/oauth2"
 )
 
-const githubAPITokenEnv = "GITHUB_API_TOKEN"
-const teamcityVCSNumberEnv = "BUILD_VCS_NUMBER"
-const targetEnv = "TARGET"
+const (
+	githubAPITokenEnv    = "GITHUB_API_TOKEN"
+	teamcityVCSNumberEnv = "BUILD_VCS_NUMBER"
+	targetEnv            = "TARGET"
+	// The following environment variables are for testing and are
+	// prefixed with GHM_ to help prevent accidentally triggering
+	// test code inside the CI pipeline.
+	packageEnv    = "GHM_PACKAGES"
+	forceBazelEnv = "GHM_FORCE_BAZEL"
+)
 
 // https://github.com/golang/go/blob/go1.7.3/src/cmd/go/test.go#L1260:L1262
 //
@@ -59,6 +67,24 @@ type pkg struct {
 	tests []string
 }
 
+func pkgsFromGithubPRForSHA(
+	ctx context.Context, org string, repo string, sha string,
+) (map[string]pkg, error) {
+	client := ghClient(ctx)
+	currentPull := findPullRequest(ctx, client, org, repo, sha)
+	if currentPull == nil {
+		log.Printf("SHA %s not found in open pull requests, skipping stress", sha)
+		return nil, nil
+	}
+
+	diff, err := getDiff(ctx, client, org, repo, *currentPull.Number)
+	if err != nil {
+		return nil, err
+	}
+
+	return pkgsFromDiff(strings.NewReader(diff))
+}
+
 // pkgsFromDiff parses a git-style diff and returns a mapping from directories
 // to tests added in those directories in the given diff.
 func pkgsFromDiff(r io.Reader) (map[string]pkg, error) {
@@ -160,6 +186,25 @@ func getDiff(
 	return diff, err
 }
 
+func parsePackagesFromEnvironment(input string) (map[string]pkg, error) {
+	const expectedFormat = "PACKAGE_NAME=TEST_NAME[,TEST_NAME...][;PACKAGE_NAME=...]"
+	pkgTestStrs := strings.Split(input, ";")
+	pkgs := make(map[string]pkg, len(pkgTestStrs))
+	for _, pts := range pkgTestStrs {
+		ptsParts := strings.Split(pts, "=")
+		if len(ptsParts) < 2 {
+			return nil, fmt.Errorf("invalid format for package environment variable: %q (expected format: %s)",
+				input, expectedFormat)
+		}
+		pkgName := ptsParts[0]
+		tests := ptsParts[1]
+		pkgs[pkgName] = pkg{
+			tests: strings.Split(tests, ","),
+		}
+	}
+	return pkgs, nil
+}
+
 func main() {
 	sha, ok := os.LookupEnv(teamcityVCSNumberEnv)
 	if !ok {
@@ -174,32 +219,34 @@ func main() {
 		log.Fatalf("environment variable %s is %s; expected 'stress' or 'stressrace'", targetEnv, target)
 	}
 
-	const org = "cockroachdb"
-	const repo = "cockroach"
+	forceBazel := false
+	if forceBazelStr, ok := os.LookupEnv(forceBazelEnv); ok {
+		forceBazel, _ = strconv.ParseBool(forceBazelStr)
+	}
 
 	crdb, err := os.Getwd()
 	if err != nil {
 		log.Fatal(err)
 	}
 
-	ctx := context.Background()
-	client := ghClient(ctx)
-
-	currentPull := findPullRequest(ctx, client, org, repo, sha)
-	if currentPull == nil {
-		log.Printf("SHA %s not found in open pull requests, skipping stress", sha)
-		return
-	}
+	var pkgs map[string]pkg
+	if pkgStr, ok := os.LookupEnv(packageEnv); ok {
+		log.Printf("Using packages from environment variable %s", packageEnv)
+		pkgs, err = parsePackagesFromEnvironment(pkgStr)
+		if err != nil {
+			log.Fatal(err)
+		}
 
-	diff, err := getDiff(ctx, client, org, repo, *currentPull.Number)
-	if err != nil {
-		log.Fatal(err)
+	} else {
+		ctx := context.Background()
+		const org = "cockroachdb"
+		const repo = "cockroach"
+		pkgs, err = pkgsFromGithubPRForSHA(ctx, org, repo, sha)
+		if err != nil {
+			log.Fatal(err)
+		}
 	}
 
-	pkgs, err := pkgsFromDiff(strings.NewReader(diff))
-	if err != nil {
-		log.Fatal(err)
-	}
 	if len(pkgs) > 0 {
 		for name, pkg := range pkgs {
 			// 20 minutes total seems OK, but at least 2 minutes per test.
@@ -224,7 +271,7 @@ func main() {
 			}
 
 			var args []string
-			if bazel.BuiltWithBazel() {
+			if bazel.BuiltWithBazel() || forceBazel {
 				args = append(args, "test")
 				// NB: We use a pretty dumb technique to list the bazel test
 				// targets: we ask bazel query to enumerate all the tests in this