Allow series and base in bundles if they match

Add a verification step into the client to ensure that series and base
match.

As such, we can treat series and bases as equivalent when they show up
precedence-wise.

Immidately combine into a base in core. As a helpful side effect, this
means we can minimise our dealing with series in this part of the code,
which will make it very easy to remove completely

cmd/juju/application/bundle/bundle.go

@@ -4,6 +4,7 @@
 package bundle
 
 import (
+	"fmt"
 	"reflect"
 	"sort"
 	"strings"
@@ -299,6 +300,11 @@ func verifyBundle(data *charm.BundleData, bundleDir string) error {
 		_, err := devices.ParseConstraints(s)
 		return err
 	}
+
+	if err := verifyMixedSeriesBasesMatch(data); err != nil {
+		return errors.Trace(err)
+	}
+
 	var verifyError error
 	if bundleDir == "" {
 		verifyError = data.Verify(verifyConstraints, verifyStorage, verifyDevices)
@@ -315,3 +321,55 @@ func verifyBundle(data *charm.BundleData, bundleDir string) error {
 	}
 	return errors.Trace(verifyError)
 }
+
+func verifyMixedSeriesBasesMatch(data *charm.BundleData) error {
+	if data == nil {
+		return nil
+	}
+	if data.Series != "" && data.DefaultBase != "" {
+		b, err := corebase.ParseBaseFromString(data.DefaultBase)
+		if err != nil {
+			return errors.Trace(err)
+		}
+		s, err := corebase.GetSeriesFromBase(b)
+		if err != nil {
+			return errors.Trace(err)
+		}
+		if s != data.Series {
+			return errors.NewNotValid(nil, fmt.Sprintf("bundle series %q and base %q must match if supplied", data.Series, data.DefaultBase))
+		}
+	}
+
+	for name, m := range data.Machines {
+		if m != nil && m.Series != "" && m.Base != "" {
+			b, err := corebase.ParseBaseFromString(m.Base)
+			if err != nil {
+				return errors.Trace(err)
+			}
+			s, err := corebase.GetSeriesFromBase(b)
+			if err != nil {
+				return errors.Trace(err)
+			}
+			if s != m.Series {
+				return errors.NewNotValid(nil, fmt.Sprintf("machine %q series %q and base %q must match if supplied", name, m.Series, m.Base))
+			}
+		}
+	}
+
+	for name, app := range data.Applications {
+		if app != nil && app.Series != "" && app.Base != "" {
+			b, err := corebase.ParseBaseFromString(app.Base)
+			if err != nil {
+				return errors.Trace(err)
+			}
+			s, err := corebase.GetSeriesFromBase(b)
+			if err != nil {
+				return errors.Trace(err)
+			}
+			if s != app.Series {
+				return errors.NewNotValid(nil, fmt.Sprintf("application %q series %q and base %q must match if supplied", name, app.Series, app.Base))
+			}
+		}
+	}
+	return nil
+}

cmd/juju/application/bundle/bundle_test.go

@@ -263,6 +263,30 @@ func (s *composeAndVerifyRepSuite) TestComposeAndVerifyBundleOverlayUnmarshallEr
 	c.Assert(unmarshallErrors[0], gc.Equals, expectedError)
 }
 
+func (s *composeAndVerifyRepSuite) TestComposeAndVerifyBundleMixingBaseAndSeries(c *gc.C) {
+	defer s.setupMocks(c).Finish()
+	bundleData, err := charm.ReadBundleData(strings.NewReader(mixedSeriesBaseBundle))
+	c.Assert(err, jc.ErrorIsNil)
+	s.expectParts(&charm.BundleDataPart{Data: bundleData})
+	s.expectBasePath()
+
+	obtained, _, err := ComposeAndVerifyBundle(s.bundleDataSource, nil)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Assert(obtained, gc.DeepEquals, bundleData)
+}
+
+func (s *composeAndVerifyRepSuite) TestComposeAndVerifyBundleMixingBaseAndSeriesMisMatch(c *gc.C) {
+	defer s.setupMocks(c).Finish()
+	bundleData, err := charm.ReadBundleData(strings.NewReader(mixedSeriesBaseBundleMismatch))
+	c.Assert(err, jc.ErrorIsNil)
+	s.expectParts(&charm.BundleDataPart{Data: bundleData})
+	s.expectBasePath()
+
+	obtained, _, err := ComposeAndVerifyBundle(s.bundleDataSource, []string{s.overlayFile})
+	c.Assert(err, gc.ErrorMatches, `application "wordpress" series "jammy" and base "ubuntu@20.04" must match if supplied`)
+	c.Assert(obtained, gc.IsNil)
+}
+
 func (s *composeAndVerifyRepSuite) setupOverlayFile(c *gc.C) {
 	s.overlayDir = c.MkDir()
 	s.overlayFile = filepath.Join(s.overlayDir, "config.yaml")
@@ -375,29 +399,29 @@ func (m stringSliceMatcher) String() string {
 }
 
 const wordpressBundle = `
-series: bionic
+default-base: ubuntu@18.04
 applications:
   mysql:
     charm: ch:mysql
     revision: 42
     channel: stable
-    series: xenial
+    base: ubuntu@16.04
     num_units: 1
     to:
     - "0"
   wordpress:
     charm: ch:wordpress
     channel: stable
     revision: 47
-    series: xenial
+    base: ubuntu@16.04
     num_units: 1
     to:
     - "1"
 machines:
   "0":
-    series: xenial
+    base: ubuntu@16.04
   "1":
-    series: xenial
+    base: ubuntu@16.04
 relations:
 - - wordpress:db
   - mysql:db
@@ -432,3 +456,68 @@ relations:
 - - wordpress:db
   - mysql:db
 `
+
+const mixedSeriesBaseBundle = `
+series: bionic
+default-base: ubuntu@18.04
+applications:
+  mysql:
+    charm: ch:mysql
+    revision: 42
+    channel: stable
+    series: xenial
+    base: ubuntu@16.04
+    num_units: 1
+    to:
+    - "0"
+  wordpress:
+    charm: ch:wordpress
+    channel: stable
+    revision: 47
+    series: jammy
+    num_units: 1
+    to:
+    - "1"
+machines:
+  "0":
+    series: xenial
+    base: ubuntu@16.04
+  "1":
+    series: jammy
+relations:
+- - wordpress:db
+  - mysql:db
+`
+
+const mixedSeriesBaseBundleMismatch = `
+series: bionic
+default-base: ubuntu@18.04
+applications:
+  mysql:
+    charm: ch:mysql
+    revision: 42
+    channel: stable
+    series: xenial
+    base: ubuntu@16.04
+    num_units: 1
+    to:
+    - "0"
+  wordpress:
+    charm: ch:wordpress
+    channel: stable
+    revision: 47
+    series: jammy
+    base: ubuntu@20.04
+    num_units: 1
+    to:
+    - "1"
+machines:
+  "0":
+    series: xenial
+    base: ubuntu@16.04
+  "1":
+    series: jammy
+relations:
+- - wordpress:db
+  - mysql:db
+`

core/bundle/changes/changes_test.go

@@ -3756,6 +3756,17 @@ func (s *changesSuite) TestLocalCharmWithExplicitSeries(c *gc.C) {
                 charm: %s
                 series: xenial
     `, charmDir)
+	charmMeta := `
+name: multi-series
+summary: That's a dummy charm with multi-series.
+description: A dummy charm.
+series:
+    - jammy
+    - focal
+    - bionic
+`[1:]
+	err := os.WriteFile(filepath.Join(charmDir, "metadata.yaml"), []byte(charmMeta), 0644)
+	c.Assert(err, jc.ErrorIsNil)
 	s.assertLocalBundleChanges(c, charmDir, bundleContent, "xenial")
 	s.assertLocalBundleChangesWithDevices(c, charmDir, bundleContent, "xenial")
 }

core/bundle/changes/handlers.go

@@ -33,6 +33,7 @@ type resolver struct {
 func (r *resolver) handleApplications() (map[string]string, error) {
 	add := r.changes.add
 	applications := r.bundle.Applications
+	existing := r.model
 
 	var defaultSeries string
 	if r.bundle.Series != "" {
@@ -43,7 +44,6 @@ func (r *resolver) handleApplications() (map[string]string, error) {
 			return nil, errors.Trace(err)
 		}
 	}
-	existing := r.model
 
 	charms := make(map[string]string, len(applications))
 	addedApplications := make(map[string]string, len(applications))
@@ -62,7 +62,7 @@ func (r *resolver) handleApplications() (map[string]string, error) {
 			application.Series = corebase.LegacyKubernetesSeries()
 		}
 		existingApp := existing.GetApplication(name)
-		computedSeries, err := getSeries(application, defaultSeries)
+		series, err := getSeries(application, defaultSeries)
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
@@ -418,6 +418,10 @@ func (r *resolver) handleMachines() (map[string]*AddMachineChange, error) {
 	add := r.changes.add
 	machines := r.bundle.Machines
 	existing := r.model
+	defaultBase, err := computeBase(r.bundle.DefaultBase, r.bundle.Series, corebase.Base{})
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
 
 	var defaultSeries string
 	if r.bundle.Series != "" {
@@ -1190,7 +1194,7 @@ func (r *resolver) handleUnits(addedApplications map[string]string, addedMachine
 	}
 
 	processor.addAllNeededUnits()
-	err := processor.processUnitPlacement()
+	err = processor.processUnitPlacement()
 	if err != nil {
 		return errors.Trace(err)
 	}
@@ -1286,7 +1290,7 @@ func applicationKey(charm, arch, series, channel string, revision int) string {
 }
 
 // getSeries retrieves the series of a application from the ApplicationSpec or from the
-// charm path or URL if provided, otherwise falling back on a default series.
+// charm path or URL if provided.
 //
 // DEPRECATED: This should be all about bases.
 func getSeries(application *charm.ApplicationSpec, defaultSeries string) (string, error) {
@@ -1297,26 +1301,23 @@ func getSeries(application *charm.ApplicationSpec, defaultSeries string) (string
 		return baseToSeries(application.Base)
 	}
 
-	// Handle local charm paths.
 	if charm.IsValidLocalCharmOrBundlePath(application.Charm) {
 		_, charmURL, err := corecharm.NewCharmAtPath(application.Charm, defaultSeries)
 		if corecharm.IsMissingSeriesError(err) {
 			// local charm path is valid but the charm doesn't declare a default series.
-			return defaultSeries, nil
+			return "", nil
 		} else if corecharm.IsUnsupportedSeriesError(err) {
 			// The bundle's default series is not supported by the charm, but we'll
 			// use it anyway. This is no different to the case above where application.Series
 			// is used without checking for potential charm incompatibility.
-			return defaultSeries, nil
+			return "", nil
 		} else if err != nil {
 			return "", errors.Trace(err)
 		}
 		// Return the default series from the local charm.
 		return charmURL.Series, nil
 	}
 
-	// The following is safe because the bundle data is assumed to be already
-	// verified, and therefore this must be a valid charm URL.
 	charmURL, err := charm.ParseURL(application.Charm)
 	if err != nil {
 		return "", errors.Trace(err)
@@ -1328,7 +1329,7 @@ func getSeries(application *charm.ApplicationSpec, defaultSeries string) (string
 		}
 		return charmURL.Series, nil
 	}
-	return defaultSeries, nil
+	return "", nil
 }
 
 func baseToSeries(b string) (string, error) {