Fix bug in last_rc logic (bazelbuild#237)

We're going to upload rolling releases to GCS, too. While Bazelisk continues to download rolling releases from GitHub, the presence of rolling releases on GCS actually broke the resolution logic for "last_rc". This commit fixes the problem and adds test coverage for similar scenarios.

bazelisk_version_test.go

@@ -44,10 +44,11 @@ func TestMain(m *testing.M) {
 
 func TestResolveLatestRcVersion(t *testing.T) {
 	s := setUp(t)
-	s.AddVersion("4.0.0", false)
-	s.AddVersion("10.0.0", false)
-	s.AddVersion("11.0.0", true)
-	s.AddVersion("11.11.0", false, 1, 2)
+	s.AddVersion("4.0.0", false, nil, nil)
+	s.AddVersion("10.0.0", false, nil, nil)
+	s.AddVersion("11.0.0", true, nil, nil)
+	s.AddVersion("11.11.0", false, []int{1, 2}, nil)
+	s.AddVersion("12.0.0", false, nil, []string{"12.0.0-pre.20210504.1"})
 	s.Finish()
 
 	gcs := &repositories.GCSRepo{}
@@ -65,7 +66,7 @@ func TestResolveLatestRcVersion(t *testing.T) {
 
 func TestResolveLatestRcVersion_WithFullRelease(t *testing.T) {
 	s := setUp(t)
-	s.AddVersion("4.0.0", true, 1, 2, 3)
+	s.AddVersion("4.0.0", true, []int{1, 2, 3}, nil)
 	s.Finish()
 
 	gcs := &repositories.GCSRepo{}
@@ -83,9 +84,9 @@ func TestResolveLatestRcVersion_WithFullRelease(t *testing.T) {
 
 func TestResolveLatestVersion_TwoLatestVersionsDoNotHaveAReleaseYet(t *testing.T) {
 	s := setUp(t)
-	s.AddVersion("4.0.0", true)
-	s.AddVersion("5.0.0", false)
-	s.AddVersion("6.0.0", false)
+	s.AddVersion("4.0.0", true, nil, nil)
+	s.AddVersion("5.0.0", false, nil, nil)
+	s.AddVersion("6.0.0", false, nil, nil)
 	s.Finish()
 
 	gcs := &repositories.GCSRepo{}
@@ -101,12 +102,13 @@ func TestResolveLatestVersion_TwoLatestVersionsDoNotHaveAReleaseYet(t *testing.T
 	}
 }
 
-func TestResolveLatestVersion_FilterReleaseCandidates(t *testing.T) {
+func TestResolveLatestVersion_ShouldOnlyReturnStableReleases(t *testing.T) {
 	s := setUp(t)
-	s.AddVersion("3.0.0", true)
-	s.AddVersion("4.0.0", false)
-	s.AddVersion("5.0.0", false)
-	s.AddVersion("6.0.0", true)
+	s.AddVersion("3.0.0", true, []int{1}, nil)
+	s.AddVersion("4.0.0", false, nil, nil)
+	s.AddVersion("5.0.0", false, nil, nil)
+	s.AddVersion("6.0.0", true, []int{1, 2}, nil)
+	s.AddVersion("7.0.0", false, nil, []string{"12.0.0-pre.20210504.1"})
 	s.Finish()
 
 	gcs := &repositories.GCSRepo{}
@@ -124,8 +126,8 @@ func TestResolveLatestVersion_FilterReleaseCandidates(t *testing.T) {
 
 func TestResolveLatestVersion_ShouldFailIfNotEnoughReleases(t *testing.T) {
 	s := setUp(t)
-	s.AddVersion("3.0.0", true)
-	s.AddVersion("4.0.0", false)
+	s.AddVersion("3.0.0", true, nil, nil)
+	s.AddVersion("4.0.0", false, nil, nil)
 	s.Finish()
 
 	gcs := &repositories.GCSRepo{}
@@ -239,13 +241,22 @@ type gcsSetup struct {
 	test            *testing.T
 }
 
-func (g *gcsSetup) AddVersion(version string, hasRelease bool, rcs ...int) *gcsSetup {
+func (g *gcsSetup) AddVersion(version string, hasRelease bool, rcs []int, rolling []string) *gcsSetup {
 	g.versionPrefixes = append(g.versionPrefixes, fmt.Sprintf("%s/", version))
 	prefixes := make([]string, 0)
+
+	register := func(subDir string) {
+		path := fmt.Sprintf("%s/%s/", version, subDir)
+		prefixes = append(prefixes, path)
+		g.addURL(path, false)
+	}
+
 	for _, rc := range rcs {
-		prefix := fmt.Sprintf("%s/rc%d/", version, rc)
-		prefixes = append(prefixes, prefix)
-		g.addURL(prefix, false)
+		register(fmt.Sprintf("rc%d", rc))
+	}
+
+	for _, r := range rolling {
+		register(r)
 	}
 
 	// The /release/ URLs have to exist, even if there is no release. In this case GCS returns no items, though.

repositories/gcs.go

@@ -156,22 +156,28 @@ func (gcs *GCSRepo) GetCandidateVersions(bazeliskHome string) ([]string, error)
 		return []string{}, errors.New("could not find any Bazel versions")
 	}
 
-	latestVersion := history[len(history)-1]
-
-	// Append slash to match directories
-	rcPrefixes, _, err := listDirectoriesInReleaseBucket(latestVersion + "/")
-	if err != nil {
-		return []string{}, fmt.Errorf("could not list release candidates for latest release: %v", err)
-	}
+	// Find most recent directory that contains any release candidates.
+	// Typically it should be the last or second-to-last, depending on whether there are new rolling releases.
+	for pos := len(history) - 1; pos >= 0; pos-- {
+		// Append slash to match directories
+		bucket := fmt.Sprintf("%s/", history[pos])
+		rcPrefixes, _, err := listDirectoriesInReleaseBucket(bucket)
+		if err != nil {
+			return []string{}, fmt.Errorf("could not list release candidates for latest release: %v", err)
+		}
 
-	rcs := make([]string, 0)
-	for _, v := range getVersionsFromGCSPrefixes(rcPrefixes) {
-		// Remove full releases
-		if strings.Contains(v, "rc") {
-			rcs = append(rcs, v)
+		rcs := make([]string, 0)
+		for _, v := range getVersionsFromGCSPrefixes(rcPrefixes) {
+			// Remove full and rolling releases
+			if strings.Contains(v, "rc") {
+				rcs = append(rcs, v)
+			}
+		}
+		if len(rcs) > 0 {
+			return rcs, nil
 		}
 	}
-	return rcs, nil
+	return nil, nil
 }
 
 // DownloadCandidate downloads the given release candidate into the specified location and returns the absolute path.