add 'db migrate' command option to specify target version

src/cli.rs

@@ -3,7 +3,7 @@
 //! CLI argument structs are defined in this module. Execution logic for each
 //! command goes in a submodule.
 
-use std::path::PathBuf;
+use std::{path::PathBuf, str::FromStr};
 
 use clap::{Parser, Subcommand};
 
@@ -78,6 +78,23 @@ pub(crate) struct MigrateDbArgs {
     #[clap(flatten)]
     config: ConfigArg,
 
+    /// Target server implementation to migrate database to.
+    ///
+    /// If migrating to the current version of grapevine, specify the version
+    /// as 'grapevine'.
+    ///
+    /// If migrating to a released version of conduit, specified the version
+    /// of conduit as `conduit-{version}` (example: `conduit-0.8.0`). If
+    /// migrating to an unreleased conduit build, instead specify the raw
+    /// database version as `conduit-db-{version}` (example: `conduit-db-13`).
+    /// The raw database version can be found by looking at the
+    /// `latest_database_version` variable in `src/database/mod.rs`.
+    ///
+    /// The server implementation used for the current database will be
+    /// detected automatically, and does not need to be specified.
+    #[clap(long)]
+    pub(crate) to: DbMigrationTarget,
+
     /// Path to read database from.
     #[clap(long = "in", short)]
     pub(crate) in_path: PathBuf,
@@ -87,6 +104,78 @@ pub(crate) struct MigrateDbArgs {
     pub(crate) out_path: PathBuf,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum DbMigrationTarget {
+    /// The latest grapevine db version
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!("grapevine".parse(), Ok(DbMigrationTarget::Grapevine))
+    /// ```
+    Grapevine,
+    /// A conduit-compatible db version.
+    ///
+    /// This may either be specified as a released version number or directly
+    /// as a database version. The raw database version must be used when
+    /// migrating to a conduit deployment built from an unreleased commit
+    /// on the `next` branch.
+    Conduit(ConduitDbVersion),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum ConduitDbVersion {
+    /// A conduit release version number
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!(
+    ///     "conduit-0.8.0".parse(),
+    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release("0.8.0")))
+    /// );
+    /// ```
+    Release(String),
+    /// A raw database version
+    ///
+    /// This corresponds directly to a
+    /// [`crate::service::globals::DbVersion::Conduit`] version.
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!(
+    ///     "conduit-db-13".parse(),
+    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(13)))
+    /// );
+    /// ```
+    Db(u64),
+}
+
+#[derive(thiserror::Error, Debug)]
+#[error("invalid db migration target version")]
+pub(crate) struct DbMigrationTargetParseError;
+
+impl FromStr for DbMigrationTarget {
+    type Err = DbMigrationTargetParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s == "grapevine" {
+            Ok(DbMigrationTarget::Grapevine)
+        } else if let Some(version) = s.strip_prefix("conduit-db-") {
+            let version =
+                version.parse().map_err(|_| DbMigrationTargetParseError)?;
+            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(version)))
+        } else if let Some(version) = s.strip_prefix("conduit-") {
+            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release(
+                version.to_owned(),
+            )))
+        } else {
+            Err(DbMigrationTargetParseError)
+        }
+    }
+}
+
 impl Args {
     pub(crate) async fn run(self) -> Result<(), error::Main> {
         match self.command {

src/cli/migrate_db.rs

@@ -1,9 +1,34 @@
-use super::MigrateDbArgs;
+use std::cmp::Ordering;
+
+use tracing::info;
+
+use super::{ConduitDbVersion, DbMigrationTarget, MigrateDbArgs};
 use crate::{
     config, database::KeyValueDatabase, error, observability,
     service::globals::DbVersion, services, utils::copy_dir, Services,
 };
 
+impl DbMigrationTarget {
+    fn to_db_version(&self) -> Result<DbVersion, error::MigrateDbCommand> {
+        use error::MigrateDbCommand as Error;
+
+        let latest_grapevine_version = DbVersion::Grapevine(0);
+
+        match self {
+            DbMigrationTarget::Grapevine => Ok(latest_grapevine_version),
+            DbMigrationTarget::Conduit(ConduitDbVersion::Db(version)) => {
+                Ok(DbVersion::Conduit(*version))
+            }
+            DbMigrationTarget::Conduit(ConduitDbVersion::Release(version)) => {
+                match &**version {
+                    "0.8.0" => Ok(DbVersion::Conduit(13)),
+                    _ => Err(Error::TargetVersionUnsupported),
+                }
+            }
+        }
+    }
+}
+
 pub(crate) async fn run(
     args: MigrateDbArgs,
 ) -> Result<(), error::MigrateDbCommand> {
@@ -32,24 +57,53 @@ pub(crate) async fn run(
 
     services().globals.err_if_server_name_changed()?;
 
-    // Migrate from a grapevine-compatible db to a conduit-0.8.0-compatible db
+    let get_current =
+        || services().globals.database_version().map_err(Error::MigrateDb);
+    let current = get_current()?;
+    let target = args.to.to_db_version()?;
+    let latest = DbVersion::Grapevine(0);
 
-    let version =
-        services().globals.database_version().map_err(Error::MigrateDb)?;
-    if version < DbVersion::Grapevine(0) {
-        return Err(Error::DbVersionTooOld(version));
-    } else if version != DbVersion::Grapevine(0) {
-        return Err(Error::DbVersionUnsupported(version));
-    };
+    info!("Migrating from {current:?} to {target:?}");
 
-    // Undo Conduit(13) -> Grapevine(0)
-    //
-    // This is a no-op that only changes the db version namespace. Setting the
-    // version to Conduit(_) will restore the original state.
-    services()
-        .globals
-        .bump_database_version(DbVersion::Conduit(13))
-        .map_err(Error::MigrateDb)?;
+    if target == current {
+        // No-op
+    } else if target == latest {
+        // Migrate to latest grapevine
+        if !current.partial_cmp(&latest).is_some_and(Ordering::is_le) {
+            return Err(Error::DbVersionUnsupported(current));
+        }
+        db.apply_migrations().await.map_err(Error::MigrateDb)?;
+    } else if target == DbVersion::Conduit(13) {
+        // Migrate to latest grapevine so we have a consistent starting point
+        if !current.partial_cmp(&latest).is_some_and(Ordering::is_le) {
+            return Err(Error::DbVersionUnsupported(current));
+        }
+        db.apply_migrations().await.map_err(Error::MigrateDb)?;
+        assert_eq!(
+            get_current()?,
+            latest,
+            "should have migrated to latest version"
+        );
+
+        // Undo Conduit(13) -> Grapevine(0)
+        //
+        // This is a no-op that only changes the db version namespace. Setting
+        // the version to Conduit(_) will restore the original state.
+        services()
+            .globals
+            .bump_database_version(DbVersion::Conduit(13))
+            .map_err(Error::MigrateDb)?;
+    } else {
+        return Err(Error::TargetVersionUnsupported);
+    }
+
+    assert_eq!(
+        get_current()?,
+        target,
+        "should have migrated to target version"
+    );
+
+    info!("Migration successful");
 
     Ok(())
 }

src/error.rs

@@ -118,15 +118,11 @@ pub(crate) enum MigrateDbCommand {
     #[error("failed to migrate database")]
     MigrateDb(#[source] crate::utils::error::Error),
 
-    #[error(
-        "initial database version is too old for migration: {_0:?}. Try \
-         loading the database with the latest conduit release and then \
-         attempting migration again."
-    )]
-    DbVersionTooOld(DbVersion),
-
     #[error("initial database version is not supported for migration: {_0:?}")]
     DbVersionUnsupported(DbVersion),
+
+    #[error("target database version is not supported for migration")]
+    TargetVersionUnsupported,
 }
 
 /// Errors copying a directory recursively.