remove entries from versioned content map again

crates/next-api/src/versioned_content_map.rs

@@ -1,6 +1,7 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 
 use anyhow::{bail, Result};
+use indexmap::IndexSet;
 use next_core::emit_assets;
 use serde::{Deserialize, Serialize};
 use turbo_tasks::{
@@ -31,11 +32,12 @@ struct MapEntry {
 #[turbo_tasks::value(transparent)]
 struct OptionMapEntry(Option<MapEntry>);
 
-type PathToOutputOperation = HashMap<Vc<FileSystemPath>, Vc<OutputAssets>>;
+type PathToOutputOperation = HashMap<Vc<FileSystemPath>, IndexSet<Vc<OutputAssets>>>;
 type OutputOperationToComputeEntry = HashMap<Vc<OutputAssets>, Vc<OptionMapEntry>>;
 
 #[turbo_tasks::value]
 pub struct VersionedContentMap {
+    // TODO: turn into a bi-directional multimap, OutputAssets -> IndexSet<FileSystemPath>
     map_path_to_op: State<PathToOutputOperation>,
     map_op_to_compute_entry: State<OutputOperationToComputeEntry>,
 }
@@ -95,22 +97,41 @@ impl VersionedContentMap {
         client_output_path: Vc<FileSystemPath>,
     ) -> Result<Vc<OptionMapEntry>> {
         let assets = *assets_operation.await?;
-        let entries: Vec<_> = assets
-            .await?
-            .iter()
+        let assets_result = assets.await;
+
+        let entries = if let Ok(assets_ref) = assets_result {
+            assets_ref.iter()
             .map(|&asset| async move { Ok((asset.ident().path().resolve().await?, asset, assets)) })
             .try_join()
-            .await?;
+            .await?
+        } else {
+            vec![]
+        };
 
         self.await?.map_path_to_op.update_conditionally(|map| {
             let mut changed = false;
-            for &(k, _, v) in entries.iter() {
-                if map.insert(k, v) != Some(v) {
-                    changed = true;
-                }
+
+            // get current map's keys, subtract keys that don't exist in operation
+            let mut stale_assets = map.keys().copied().collect::<HashSet<_>>();
+
+            for (k, _, v) in entries.iter() {
+                let res = map.entry(*k).or_default().insert(*v);
+                stale_assets.remove(k);
+                changed = changed || res;
+            }
+
+            // Make more efficient with reverse map
+            for k in &stale_assets {
+                let res = map
+                    .get_mut(k)
+                    // guaranteed
+                    .unwrap()
+                    .remove(&assets);
+                changed = changed || res
             }
             changed
         });
+
         // Make sure all written client assets are up-to-date
         let side_effects = emit_assets(assets, node_root, client_relative_path, client_output_path);
         let map_entry = Vc::cell(Some(MapEntry {
@@ -193,7 +214,7 @@ impl VersionedContentMap {
     async fn raw_get(&self, path: Vc<FileSystemPath>) -> Result<Vc<OptionMapEntry>> {
         let assets = {
             let map = self.map_path_to_op.get();
-            map.get(&path).copied()
+            map.get(&path).and_then(|m| m.iter().last().copied())
         };
         let Some(assets) = assets else {
             return Ok(Vc::cell(None));