"db newer than app" guard

src-tauri/src/db/mod.rs

@@ -1,9 +1,12 @@
+use sqlx::migrate::Migrator;
 use sqlx::sqlite::{SqliteConnectOptions, SqliteJournalMode, SqlitePoolOptions};
 use sqlx::{Pool, Sqlite};
 use std::error::Error;
 use tauri::{AppHandle, Manager};
+use tauri_plugin_dialog::{DialogExt, MessageDialogButtons, MessageDialogKind};
 
 const DATABASE_FILE: &str = "friendolls.sqlite";
+static MIGRATOR: Migrator = sqlx::migrate!("./migrations");
 
 pub struct AppDatabase {
     pool: Pool<Sqlite>,
@@ -35,14 +38,92 @@ pub async fn init(app: &AppHandle) -> Result<(), Box<dyn Error>> {
         .connect_with(options)
         .await?;
 
-    sqlx::migrate!("./migrations").run(&pool).await?;
+    if database_requires_newer_app(&pool).await? {
+        show_outdated_app_dialog(app);
+        return std::future::pending().await;
+    }
+
+    MIGRATOR.run(&pool).await?;
 
     app.manage(AppDatabase::new(pool));
 
     Ok(())
 }
 
+async fn database_requires_newer_app(pool: &Pool<Sqlite>) -> Result<bool, sqlx::Error> {
+    let has_migration_history = sqlx::query_scalar::<_, bool>(
+        "SELECT EXISTS(SELECT 1 FROM sqlite_master WHERE type = 'table' AND name = '_sqlx_migrations')",
+    )
+    .fetch_one(pool)
+    .await?;
+
+    if !has_migration_history {
+        return Ok(false);
+    }
+
+    let latest_applied =
+        sqlx::query_scalar::<_, Option<i64>>("SELECT MAX(version) FROM _sqlx_migrations")
+            .fetch_one(pool)
+            .await?;
+    let latest_supported = MIGRATOR.iter().map(|migration| migration.version).max();
+
+    Ok(latest_applied
+        .zip(latest_supported)
+        .is_some_and(|(applied, supported)| applied > supported))
+}
+
+fn show_outdated_app_dialog(app: &AppHandle) {
+    app.dialog()
+        .message(
+            "Your on-device data was created by a newer version of Friendolls and cannot be opened safely by this version.\n\nDownload and install the latest version of Friendolls, then reopen the app. Your data has not been changed.",
+        )
+        .title("Friendolls is out of date")
+        .kind(MessageDialogKind::Warning)
+        .buttons(MessageDialogButtons::OkCustom("Close Friendolls".into()))
+        .show(move |_| std::process::exit(0));
+}
+
 #[inline]
 pub fn command_error(error: impl std::fmt::Display) -> String {
     error.to_string()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn database_without_migration_history_does_not_require_newer_app() {
+        let pool = SqlitePoolOptions::new()
+            .connect("sqlite::memory:")
+            .await
+            .expect("connect to in-memory database");
+
+        assert!(!database_requires_newer_app(&pool).await.unwrap());
+    }
+
+    #[tokio::test]
+    async fn database_with_newer_migration_requires_newer_app() {
+        let pool = SqlitePoolOptions::new()
+            .connect("sqlite::memory:")
+            .await
+            .expect("connect to in-memory database");
+        sqlx::query("CREATE TABLE _sqlx_migrations (version BIGINT PRIMARY KEY)")
+            .execute(&pool)
+            .await
+            .expect("create migration history");
+        let newer_version = MIGRATOR
+            .iter()
+            .map(|migration| migration.version)
+            .max()
+            .expect("at least one embedded migration")
+            + 1;
+        sqlx::query("INSERT INTO _sqlx_migrations (version) VALUES (?)")
+            .bind(newer_version)
+            .execute(&pool)
+            .await
+            .expect("insert newer migration");
+
+        assert!(database_requires_newer_app(&pool).await.unwrap());
+    }
+}