controllers/krate/publish: Always upsert the default_value

The value is determined by comparing the existing `default_value` to the
published version. This could potentially result in upserting an
outdated version. A subsequent background job is necessary to ensure
correctness and eventual consistency.

Author: eth3lbert

src/controllers/krate/publish.rs

@@ -23,6 +23,7 @@ use tokio::runtime::Handle;
 use url::Url;
 
 use crate::models::{
+    default_versions::{find_default_version, Version as DefaultVersion},
     insert_version_owner_action, Category, Crate, DependencyKind, Keyword, NewCrate, NewVersion,
     Rights, VersionAction,
 };
@@ -64,7 +65,7 @@ pub async fn publish(app: AppState, req: BytesRequest) -> AppResult<Json<GoodCra
 
     Crate::validate_crate_name("crate", &metadata.name).map_err(bad_request)?;
 
-    let version = match semver::Version::parse(&metadata.vers) {
+    let semver = match semver::Version::parse(&metadata.vers) {
         Ok(parsed) => parsed,
         Err(_) => {
             return Err(bad_request(format_args!(
@@ -75,7 +76,7 @@ pub async fn publish(app: AppState, req: BytesRequest) -> AppResult<Json<GoodCra
     };
 
     // Convert the version back to a string to deal with any inconsistencies
-    let version_string = version.to_string();
+    let version_string = semver.to_string();
 
     let request_log = req.request_log();
     request_log.add("crate_name", &*metadata.name);
@@ -385,16 +386,41 @@ pub async fn publish(app: AppState, req: BytesRequest) -> AppResult<Json<GoodCra
             // Link this new version to all dependencies
             add_dependencies(conn, &deps, version.id)?;
 
-            // Insert the default version if it doesn't already exist. Compared
-            // to only using a background job, this prevents us from getting
-            // into a situation where a crate exists in the `crates` table but
-            // doesn't have a default version in the `default_versions` table.
-            let inserted_default_versions = diesel::insert_into(default_versions::table)
+            let existing_default_version = default_versions::table
+                .inner_join(versions::table)
+                .filter(default_versions::crate_id.eq(krate.id))
+                .select(DefaultVersion::as_select())
+                .first(conn)
+                .optional()?;
+
+            let published_default_version = DefaultVersion {
+                id: version.id,
+                num: semver,
+                yanked: false,
+            };
+
+            // Upsert the `default_value` determined by the existing `default_value` and the
+            // published version. Note that this could potentially write an outdated version
+            // (although this should not happen regularly), as we might be comparing to an
+            // outdated value.
+            //
+            // Compared to only using a background job, this prevents us from getting into a
+            // situation where a crate exists in the `crates` table but doesn't have a default
+            // version in the `default_versions` table.
+            let default_version = if let Some(default_version) = existing_default_version {
+                find_default_version(&[default_version, published_default_version]).cloned()
+                    .expect("at least published version should be chosen")
+            } else {
+                published_default_version
+            };
+            diesel::insert_into(default_versions::table)
                 .values((
                     default_versions::crate_id.eq(krate.id),
-                    default_versions::version_id.eq(version.id),
+                    default_versions::version_id.eq(default_version.id),
                 ))
-                .on_conflict_do_nothing()
+                .on_conflict(default_versions::crate_id)
+                .do_update()
+                .set(default_versions::version_id.eq(default_version.id))
                 .execute(conn)?;
 
             // Update all keywords for this crate
@@ -446,11 +472,9 @@ pub async fn publish(app: AppState, req: BytesRequest) -> AppResult<Json<GoodCra
 
             SendPublishNotificationsJob::new(version.id).enqueue(conn)?;
 
-            // If this is a new version for an existing crate it is sufficient
-            // to update the default version asynchronously in a background job.
-            if inserted_default_versions == 0 {
-                UpdateDefaultVersion::new(krate.id).enqueue(conn)?;
-            }
+            // Update the default version asynchronously in a background job
+            // to ensure correctness and eventual consistency.
+            UpdateDefaultVersion::new(krate.id).enqueue(conn)?;
 
             // Experiment: check new crates for potential typosquatting.
             if existing_crate.is_none() {