[BEAM-14029] Add getter, setter for target maven repo (#16995)

sdks/go/pkg/beam/core/runtime/xlangx/expansionx/download.go

@@ -50,13 +50,43 @@ func newJarGetter() *jarGetter {
 	return &jarGetter{repository: apacheRepository, groupID: beamGroupID, jarCache: cacheDir}
 }
 
+// GetRepositoryURL returns the current target URL for the defaultJarGetter,
+// indicating what repository will be connected to when getting a Beam JAR.
+func GetDefaultRepositoryURL() string {
+	return defaultJarGetter.getRepositoryURL()
+}
+
+// SetRepositoryURL updates the target URL for the defaultJarGetter, changing
+// which Maven repository will be connected to when getting a Beam JAR. Also
+// validates that it has been passed a URL and returns an error if not.
+//
+// When changing the target repository, make sure that the value is the prefix
+// up to "org/apache/beam" and that the organization of the repository matches
+// that of the default from that point on to ensure that the conversion of the
+// Gradle target to the JAR name is correct.
+func SetDefaultRepositoryURL(repoURL string) error {
+	return defaultJarGetter.setRepositoryURL(repoURL)
+}
+
 // GetBeamJar checks a temporary directory for the desired Beam JAR, downloads the
 // appropriate JAR from Maven if not present, then returns the file path to the
 // JAR.
 func GetBeamJar(gradleTarget, version string) (string, error) {
 	return defaultJarGetter.getJar(gradleTarget, version)
 }
 
+func (j *jarGetter) getRepositoryURL() string {
+	return string(j.repository)
+}
+
+func (j *jarGetter) setRepositoryURL(repoURL string) error {
+	if !strings.HasPrefix(repoURL, "http") {
+		return fmt.Errorf("repo URL %v does not have an http or https prefix", repoURL)
+	}
+	j.repository = url(strings.TrimSuffix(repoURL, "/"))
+	return nil
+}
+
 func (j *jarGetter) getJar(gradleTarget, version string) (string, error) {
 	strippedTarget := dropEndOfGradleTarget(gradleTarget)
 	fullURL, jarName := j.getURLForBeamJar(strippedTarget, version)
@@ -84,7 +114,7 @@ func (j *jarGetter) getJar(gradleTarget, version string) (string, error) {
 	defer resp.Body.Close()
 
 	if resp.StatusCode != 200 {
-		return "", fmt.Errorf("received non 200 response code, got %v", resp.StatusCode)
+		return "", fmt.Errorf("failed to connect to %v: received non 200 response code, got %v", fullURL, resp.StatusCode)
 	}
 
 	file, err := os.Create(jarPath)

sdks/go/pkg/beam/core/runtime/xlangx/expansionx/download_test.go

@@ -23,6 +23,72 @@ import (
 	"testing"
 )
 
+func TestGetAndSetRepositoryURL(t *testing.T) {
+	tests := []struct {
+		name    string
+		newRepo string
+		expRepo string
+	}{
+		{
+			"correct URL",
+			"http://new.repo.org",
+			"http://new.repo.org",
+		},
+		{
+			"correct URL https",
+			"https://new.repo.org",
+			"https://new.repo.org",
+		},
+		{
+			"correct URL with trailing backslash",
+			"http://new.repo.org/",
+			"http://new.repo.org",
+		},
+		{
+			"correct URL https with trailing backslash",
+			"https://new.repo.org/",
+			"https://new.repo.org",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			j := newJarGetter()
+			err := j.setRepositoryURL(test.newRepo)
+			if err != nil {
+				t.Errorf("failed to set repository URL, got %v", err)
+			}
+			if got, want := j.getRepositoryURL(), test.expRepo; got != want {
+				t.Errorf("getRepositoryURL() got %v, want %v", got, want)
+			}
+		})
+	}
+}
+
+func TestGetAndSetRepositoryURL_bad(t *testing.T) {
+	tests := []struct {
+		name    string
+		newRepo string
+	}{
+		{
+			"no http",
+			"new.maven.repo.com",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			j := newJarGetter()
+			err := j.setRepositoryURL(test.newRepo)
+			if err == nil {
+				t.Errorf("setRepositoryURL(%v) succeeded when it should have failed", test.newRepo)
+			}
+			// Check that the failed Set call did not change the URL.
+			if got, want := j.getRepositoryURL(), string(apacheRepository); got != want {
+				t.Errorf("getRepositoryURL() got %v, want %v", got, want)
+			}
+		})
+	}
+}
+
 func TestGetURLForBeamJar(t *testing.T) {
 	tests := []struct {
 		name        string