Add support for charm-user.

meta.go

@@ -249,6 +249,16 @@ func (r Relation) IsImplicit() bool {
 		r.Role == RoleProvider)
 }
 
+// RunAs defines which user to run a certain process as.
+type RunAs string
+
+const (
+	RunAsDefault RunAs = ""
+	RunAsRoot    RunAs = "root"
+	RunAsSudoer  RunAs = "sudoer"
+	RunAsNonRoot RunAs = "non-root"
+)
+
 // Meta represents all the known content that may be defined
 // within a charm's metadata.yaml file.
 // Note: Series is serialised for backward compatibility
@@ -280,6 +290,7 @@ type Meta struct {
 	// v2
 	Containers map[string]Container    `bson:"containers,omitempty" json:"containers,omitempty" yaml:"containers,omitempty"`
 	Assumes    *assumes.ExpressionTree `bson:"assumes,omitempty" json:"assumes,omitempty" yaml:"assumes,omitempty"`
+	CharmUser  RunAs                   `bson:"charm-user,omitempty" json:"charm-user,omitempty" yaml:"charm-user,omitempty"`
 }
 
 // Container specifies the possible systems it supports and mounts it wants.
@@ -563,13 +574,9 @@ func parseMeta(m map[string]interface{}) (*Meta, error) {
 		return nil, err
 	}
 	meta.PayloadClasses = parsePayloadClasses(m["payloads"])
-
-	if ver := m["min-juju-version"]; ver != nil {
-		minver, err := version.Parse(ver.(string))
-		if err != nil {
-			return &meta, errors.Annotate(err, "invalid min-juju-version")
-		}
-		meta.MinJujuVersion = minver
+	meta.MinJujuVersion, err = parseMinJujuVersion(m["min-juju-version"])
+	if err != nil {
+		return nil, err
 	}
 	meta.Terms = parseStringList(m["terms"])
 
@@ -583,6 +590,10 @@ func parseMeta(m map[string]interface{}) (*Meta, error) {
 	if err != nil {
 		return nil, errors.Annotatef(err, "parsing containers")
 	}
+	meta.CharmUser, err = parseCharmUser(m["charm-user"])
+	if err != nil {
+		return nil, errors.Annotatef(err, "parsing charm-user")
+	}
 	return &meta, nil
 }
 
@@ -1224,6 +1235,31 @@ func parseMounts(input interface{}, storage map[string]Storage) ([]Mount, error)
 	return mounts, nil
 }
 
+func parseMinJujuVersion(value any) (version.Number, error) {
+	if value == nil {
+		return version.Zero, nil
+	}
+	ver, err := version.Parse(value.(string))
+	if err != nil {
+		return version.Zero, errors.Annotate(err, "invalid min-juju-version")
+	}
+	return ver, nil
+}
+
+func parseCharmUser(value any) (RunAs, error) {
+	if value == nil {
+		return RunAsDefault, nil
+	}
+	v := RunAs(value.(string))
+	switch v {
+	case RunAsRoot, RunAsSudoer, RunAsNonRoot:
+		return v, nil
+	default:
+		return RunAsDefault, errors.Errorf("invalid charm-user %q expected one of %s, %s or %s", v,
+			RunAsRoot, RunAsSudoer, RunAsNonRoot)
+	}
+}
+
 var storageSchema = schema.FieldMap(
 	schema.Fields{
 		"type":      schema.OneOf(schema.Const(string(StorageBlock)), schema.Const(string(StorageFilesystem))),
@@ -1405,6 +1441,7 @@ var charmSchema = schema.FieldMap(
 		"min-juju-version": schema.String(),
 		"assumes":          schema.List(schema.Any()),
 		"containers":       schema.StringMap(containerSchema),
+		"charm-user":       schema.String(),
 	},
 	schema.Defaults{
 		"provides":         schema.Omit,
@@ -1426,6 +1463,7 @@ var charmSchema = schema.FieldMap(
 		"min-juju-version": schema.Omit,
 		"assumes":          schema.Omit,
 		"containers":       schema.Omit,
+		"charm-user":       schema.Omit,
 	},
 )
 
@@ -1449,7 +1487,7 @@ func ensureUnambiguousFormat(raw map[interface{}]interface{}) error {
 	for _, key := range keys {
 		detected := FormatUnknown
 		switch key {
-		case "containers", "assumes":
+		case "containers", "assumes", "charm-user":
 			detected = FormatV2
 		case "series", "deployment", "min-juju-version":
 			detected = FormatV1

meta_test.go

@@ -2050,3 +2050,48 @@ func (FormatMetaSuite) TestCheckV2WithDeployment(c *gc.C) {
 	err := meta.Check(charm.FormatV2, charm.SelectionManifest, charm.SelectionBases)
 	c.Assert(err, gc.ErrorMatches, `deployment in metadata v2 not valid`)
 }
+
+func (s *MetaSuite) TestCharmUser(c *gc.C) {
+	meta, err := charm.ReadMeta(strings.NewReader(`
+name: a
+summary: b
+description: c
+charm-user: root
+`))
+	c.Assert(err, gc.IsNil)
+	c.Assert(meta.CharmUser, gc.Equals, charm.RunAsRoot)
+
+	meta, err = charm.ReadMeta(strings.NewReader(`
+name: a
+summary: b
+description: c
+charm-user: sudoer
+`))
+	c.Assert(err, gc.IsNil)
+	c.Assert(meta.CharmUser, gc.Equals, charm.RunAsSudoer)
+
+	meta, err = charm.ReadMeta(strings.NewReader(`
+name: a
+summary: b
+description: c
+charm-user: non-root
+`))
+	c.Assert(err, gc.IsNil)
+	c.Assert(meta.CharmUser, gc.Equals, charm.RunAsNonRoot)
+
+	meta, err = charm.ReadMeta(strings.NewReader(`
+name: a
+summary: b
+description: c
+`))
+	c.Assert(err, gc.IsNil)
+	c.Assert(meta.CharmUser, gc.Equals, charm.RunAsDefault)
+
+	_, err = charm.ReadMeta(strings.NewReader(`
+name: a
+summary: b
+description: c
+charm-user: barry
+`))
+	c.Assert(err, gc.ErrorMatches, `parsing charm-user: invalid charm-user "barry" expected one of root, sudoer or non-root`)
+}