fix: Do not validate the current image tag against SemVer (#1473)

Signed-off-by: Christian Schlichtherle <christian@schlichtherle.de>

Author: christian-schlichtherle

CHANGELOG.md

@@ -29,6 +29,7 @@ handling on your side.
 
 * refactor: make argocd-image-updater-config volume mapping optional (#145)
 * enhancement: sort Helm parameters alphabetically in .argocd-source-<appName>.yaml for deterministic output
+* enhancement: the current image tag no longer needs to be a valid semver version when using the semver update strategy
 
 ## 2020-12-06 - Release v0.8.0
 

docs/basics/update-strategies.md

@@ -93,9 +93,12 @@ The above example would update to any new tag pushed to the registry matching
 this constraint, e.g. `1.2.5`, `1.2.12` etc., but not to a new minor version
 (e.g. `1.3`).
 
-!!!warning "A note on the current image tag"
-    For semver strategy to work, the current application tag must already follow
-    semver. Otherwise, no comparison can happen by the updater. See discussion at [#270](https://github.com/argoproj-labs/argocd-image-updater/issues/270) for more details.
+!!!note "A note on the current image tag"
+    The current application tag does not need to follow semver. The updater will
+    find the newest tag from the registry that matches the version constraint,
+    regardless of the format of the currently running tag. For example, an
+    application running the `latest` tag can be updated to a semver-compatible
+    version using a constraint like `1.x`.
 
 Likewise, to allow updates to any minor release within the major version `1`,
 use

registry-scanner/pkg/image/version.go

@@ -106,24 +106,11 @@ func (img *ContainerImage) GetNewestVersionFromTags(ctx context.Context, vc *Ver
 	// The given constraint MUST match a semver constraint
 	var semverConstraint *semver.Constraints
 	var err error
-	if vc.Strategy == StrategySemVer {
-		// TODO: Shall we really ensure a valid semver on the current tag?
-		// This prevents updating from a non-semver tag currently.
-		if img.ImageTag != nil && img.ImageTag.TagName != "" {
-			_, err := semver.NewVersion(img.ImageTag.TagName)
-			if err != nil {
-				return nil, err
-			}
-		}
-
-		if vc.Constraint != "" {
-			if vc.Strategy == StrategySemVer {
-				semverConstraint, err = semver.NewConstraint(vc.Constraint)
-				if err != nil {
-					logCtx.Errorf("invalid constraint '%s' given: '%v'", vc, err)
-					return nil, err
-				}
-			}
+	if vc.Strategy == StrategySemVer && vc.Constraint != "" {
+		semverConstraint, err = semver.NewConstraint(vc.Constraint)
+		if err != nil {
+			logCtx.Errorf("invalid constraint '%s' given: '%v'", vc, err)
+			return nil, err
 		}
 	}
 

registry-scanner/pkg/image/version_test.go

@@ -59,6 +59,26 @@ func Test_LatestVersion(t *testing.T) {
 		assert.Equal(t, "1.0.1", newTag.TagName)
 	})
 
+	t.Run("Find the latest version with a non-semver current tag and semver constraint", func(t *testing.T) {
+		tagList := newImageTagList([]string{"0.1", "0.5.1", "0.9", "1.0", "1.0.1", "1.1.2", "2.0.3"})
+		img := NewFromIdentifier("christianschlichtherle/test:latest")
+		vc := VersionConstraint{Constraint: "^1.0"}
+		newTag, err := img.GetNewestVersionFromTags(context.Background(), &vc, tagList)
+		require.NoError(t, err)
+		require.NotNil(t, newTag)
+		assert.Equal(t, "1.1.2", newTag.TagName)
+	})
+
+	t.Run("Find the latest version with a non-semver current tag without any constraint", func(t *testing.T) {
+		tagList := newImageTagList([]string{"0.1", "0.5.1", "0.9", "1.0", "1.0.1", "1.1.2", "2.0.3"})
+		img := NewFromIdentifier("christianschlichtherle/test:latest")
+		vc := VersionConstraint{}
+		newTag, err := img.GetNewestVersionFromTags(context.Background(), &vc, tagList)
+		require.NoError(t, err)
+		require.NotNil(t, newTag)
+		assert.Equal(t, "2.0.3", newTag.TagName)
+	})
+
 	t.Run("Find the latest version with a semver constraint that has no match", func(t *testing.T) {
 		tagList := newImageTagList([]string{"0.1", "0.5.1", "0.9", "2.0.3"})
 		img := NewFromIdentifier("jannfis/test:1.0")