collab: Allow starting a trial from Zed Free (#30970)

This PR makes it so a user can initiate a checkout session for a Zed Pro
trial while on the Zed Free plan.

Release Notes:

- N/A

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/collab/src/api/billing.rs

@@ -280,7 +280,7 @@ async fn list_billing_subscriptions(
     }))
 }
 
-#[derive(Debug, Clone, Copy, Deserialize)]
+#[derive(Debug, PartialEq, Clone, Copy, Deserialize)]
 #[serde(rename_all = "snake_case")]
 enum ProductCode {
     ZedPro,
@@ -325,12 +325,17 @@ async fn create_billing_subscription(
         ))?
     };
 
-    if app.db.has_active_billing_subscription(user.id).await? {
+    if let Some(existing_subscription) = app.db.get_active_billing_subscription(user.id).await? {
+        let is_checkout_allowed = body.product == ProductCode::ZedProTrial
+            && existing_subscription.kind == Some(SubscriptionKind::ZedFree);
+
+        if !is_checkout_allowed {
             return Err(Error::http(
                 StatusCode::CONFLICT,
                 "user already has an active subscription".into(),
             ));
         }
+    }
 
     let existing_billing_customer = app.db.get_billing_customer_by_user_id(user.id).await?;
     if let Some(existing_billing_customer) = &existing_billing_customer {
@@ -1135,6 +1140,29 @@ async fn sync_subscription(
                 },
             )
             .await?;
+    } else {
+        if let Some(existing_subscription) = app
+            .db
+            .get_active_billing_subscription(billing_customer.user_id)
+            .await?
+        {
+            if existing_subscription.kind == Some(SubscriptionKind::ZedFree)
+                && subscription_kind == Some(SubscriptionKind::ZedProTrial)
+            {
+                let stripe_subscription_id = existing_subscription
+                    .stripe_subscription_id
+                    .parse::<stripe::SubscriptionId>()
+                    .context("failed to parse Stripe subscription ID from database")?;
+
+                Subscription::cancel(
+                    &stripe_client,
+                    &stripe_subscription_id,
+                    stripe::CancelSubscription {
+                        invoice_now: None,
+                        ..Default::default()
+                    },
+                )
+                .await?;
             } else {
                 // If the user already has an active billing subscription, ignore the
                 // event and return an `Ok` to signal that it was processed
@@ -1150,11 +1178,7 @@ async fn sync_subscription(
                 //   5. User ends up with no subscriptions
                 //
                 // In theory this situation shouldn't arise as we try to process the events in the order they occur.
-        if app
-            .db
-            .has_active_billing_subscription(billing_customer.user_id)
-            .await?
-        {
+
                 log::info!(
                     "user {user_id} already has an active subscription, skipping creation of subscription {subscription_id}",
                     user_id = billing_customer.user_id,
@@ -1162,6 +1186,7 @@ async fn sync_subscription(
                 );
                 return Ok(billing_customer);
             }
+        }
 
         app.db
             .create_billing_subscription(&CreateBillingSubscriptionParams {

crates/collab/src/db/queries/billing_subscriptions.rs

@@ -236,7 +236,9 @@ impl Database {
                 .filter(
                     billing_customer::Column::UserId.eq(user_id).and(
                         billing_subscription::Column::StripeSubscriptionStatus
-                            .eq(StripeSubscriptionStatus::Active),
+                            .eq(StripeSubscriptionStatus::Active)
+                            .or(billing_subscription::Column::StripeSubscriptionStatus
+                                .eq(StripeSubscriptionStatus::Trialing)),
                     ),
                 )
                 .count(&*tx)