[feature] Report Masto version in /api/v1/instance (#1977)

3 files changed, 39 insertions, 0 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 53514e20b..cb158cdad 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -80,6 +80,7 @@ type Configuration struct {
 	InstanceExposeSuspendedWeb     bool `name:"instance-expose-suspended-web" usage:"Expose list of suspended instances as webpage on /about/suspended"`
 	InstanceExposePublicTimeline   bool `name:"instance-expose-public-timeline" usage:"Allow unauthenticated users to query /api/v1/timelines/public"`
 	InstanceDeliverToSharedInboxes bool `name:"instance-deliver-to-shared-inboxes" usage:"Deliver federated messages to shared inboxes, if they're available."`
+	InstanceInjectMastodonVersion  bool `name:"instance-inject-mastodon-version" usage:"This injects a Mastodon compatible version in /api/v1/instance to help Mastodon clients that use that version for feature detection"`
 
 	AccountsRegistrationOpen bool `name:"accounts-registration-open" usage:"Allow anyone to submit an account signup request. If false, server will be invite-only."`
 	AccountsApprovalRequired bool `name:"accounts-approval-required" usage:"Do account signups require approval by an admin or moderator before user can log in? If false, new registrations will be automatically approved."`
diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index 6cd2d6bd4..ceb115bba 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -849,6 +849,31 @@ func GetInstanceDeliverToSharedInboxes() bool { return global.GetInstanceDeliver
 // SetInstanceDeliverToSharedInboxes safely sets the value for global configuration 'InstanceDeliverToSharedInboxes' field
 func SetInstanceDeliverToSharedInboxes(v bool) { global.SetInstanceDeliverToSharedInboxes(v) }
 
+// GetInstanceInjectMastodonVersion safely fetches the Configuration value for state's 'InstanceInjectMastodonVersion' field
+func (st *ConfigState) GetInstanceInjectMastodonVersion() (v bool) {
+	st.mutex.RLock()
+	v = st.config.InstanceInjectMastodonVersion
+	st.mutex.RUnlock()
+	return
+}
+
+// SetInstanceInjectMastodonVersion safely sets the Configuration value for state's 'InstanceInjectMastodonVersion' field
+func (st *ConfigState) SetInstanceInjectMastodonVersion(v bool) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.InstanceInjectMastodonVersion = v
+	st.reloadToViper()
+}
+
+// InstanceInjectMastodonVersionFlag returns the flag name for the 'InstanceInjectMastodonVersion' field
+func InstanceInjectMastodonVersionFlag() string { return "instance-inject-mastodon-version" }
+
+// GetInstanceInjectMastodonVersion safely fetches the value for global configuration 'InstanceInjectMastodonVersion' field
+func GetInstanceInjectMastodonVersion() bool { return global.GetInstanceInjectMastodonVersion() }
+
+// SetInstanceInjectMastodonVersion safely sets the value for global configuration 'InstanceInjectMastodonVersion' field
+func SetInstanceInjectMastodonVersion(v bool) { global.SetInstanceInjectMastodonVersion(v) }
+
 // GetAccountsRegistrationOpen safely fetches the Configuration value for state's 'AccountsRegistrationOpen' field
 func (st *ConfigState) GetAccountsRegistrationOpen() (v bool) {
 	st.mutex.RLock()
diff --git a/internal/typeutils/internaltofrontend.go b/internal/typeutils/internaltofrontend.go
index d6da9493f..17b8047e9 100644
--- a/internal/typeutils/internaltofrontend.go
+++ b/internal/typeutils/internaltofrontend.go
@@ -45,6 +45,7 @@ const (
 	instanceAccountsMaxFeaturedTags             = 10
 	instanceAccountsMaxProfileFields            = 6 // FIXME: https://github.com/superseriousbusiness/gotosocial/issues/1876
 	instanceSourceURL                           = "https://github.com/superseriousbusiness/gotosocial"
+	instanceMastodonVersion                     = "3.5.3"
 )
 
 var instanceStatusesSupportedMimeTypes = []string{
@@ -52,6 +53,10 @@ var instanceStatusesSupportedMimeTypes = []string{
 	string(apimodel.StatusContentTypeMarkdown),
 }
 
+func toMastodonVersion(in string) string {
+	return instanceMastodonVersion + "+" + strings.ReplaceAll(in, " ", "-")
+}
+
 func (c *converter) AccountToAPIAccountSensitive(ctx context.Context, a *gtsmodel.Account) (*apimodel.Account, error) {
 	// we can build this sensitive account easily by first getting the public account....
 	apiAccount, err := c.AccountToAPIAccountPublic(ctx, a)
@@ -740,6 +745,10 @@ func (c *converter) InstanceToAPIV1Instance(ctx context.Context, i *gtsmodel.Ins
 		MaxTootChars:     uint(config.GetStatusesMaxChars()),
 	}
 
+	if config.GetInstanceInjectMastodonVersion() {
+		instance.Version = toMastodonVersion(instance.Version)
+	}
+
 	// configuration
 	instance.Configuration.Statuses.MaxCharacters = config.GetStatusesMaxChars()
 	instance.Configuration.Statuses.MaxMediaAttachments = config.GetStatusesMediaMaxFiles()
@@ -839,6 +848,10 @@ func (c *converter) InstanceToAPIV2Instance(ctx context.Context, i *gtsmodel.Ins
 		Rules:         []interface{}{},            // todo: not implemented
 	}
 
+	if config.GetInstanceInjectMastodonVersion() {
+		instance.Version = toMastodonVersion(instance.Version)
+	}
+
 	// thumbnail
 	thumbnail := apimodel.InstanceV2Thumbnail{}