fix: avoid caching transform result of invalidated module

packages/vite/src/node/server/moduleGraph.ts

@@ -32,6 +32,7 @@ export class ModuleNode {
   ssrTransformResult: TransformResult | null = null
   ssrModule: Record<string, any> | null = null
   lastHMRTimestamp = 0
+  lastInvalidationTimestamp = 0
 
   constructor(url: string) {
     this.url = url
@@ -94,17 +95,26 @@ export class ModuleGraph {
     }
   }
 
-  invalidateModule(mod: ModuleNode, seen: Set<ModuleNode> = new Set()): void {
-    mod.info = undefined
+  invalidateModule(
+    mod: ModuleNode,
+    seen: Set<ModuleNode> = new Set(),
+    timestamp: number = Date.now()
+  ): void {
+    // Save the timestamp for this invalidation, so we can avoid caching the result of possible already started
+    // processing being done for this module
+    mod.lastInvalidationTimestamp = timestamp
+    // Don't invalidate mod.info and mod.meta, as they are part of the processing pipeline
+    // Invalidating the transform result is enough to ensure this module is re-processed next time it is requested
     mod.transformResult = null
     mod.ssrTransformResult = null
     invalidateSSRModule(mod, seen)
   }
 
   invalidateAll(): void {
+    const timestamp = Date.now()
     const seen = new Set<ModuleNode>()
     this.idToModuleMap.forEach((mod) => {
-      this.invalidateModule(mod, seen)
+      this.invalidateModule(mod, seen, timestamp)
     })
   }
 

packages/vite/src/node/server/transformRequest.ts

@@ -81,6 +81,25 @@ async function doTransform(
     return cached
   }
 
+  // This module may get invalidated while we are processing it. For example
+  // when a full page reload is needed after the re-processing of pre-bundled
+  // dependencies when a missing dep is discovered. We save the current time
+  // to compare it to the last invalidation performed to know if we should
+  // cache the result of the transformation or we should discard it as stale.
+  //
+  // A module can be invalidated due to:
+  // 1. A full reload because of pre-bundling newly discovered deps
+  // 2. A full reload after a config change
+  // 3. The file that generated the module changed
+  // 4. Invalidation for a virtual module
+  //
+  // For 1 and 2, a new request for this module will be issued after
+  // the invalidation as part of the browser reloading the page. For 3 and 4
+  // there may not be a new request right away because of HMR handling.
+  // In all cases, the next time this module is requested, it should be
+  // re-processed.
+  const timestamp = Date.now()
+
   // resolve
   const id =
     (await pluginContainer.resolveId(url, undefined, { ssr }))?.id || url
@@ -179,17 +198,20 @@ async function doTransform(
     }
   }
 
-  if (ssr) {
-    return (mod.ssrTransformResult = await ssrTransform(
-      code,
-      map as SourceMap,
-      url
-    ))
-  } else {
-    return (mod.transformResult = {
-      code,
-      map,
-      etag: getEtag(code, { weak: true })
-    } as TransformResult)
+  const result = ssr
+    ? await ssrTransform(code, map as SourceMap, url)
+    : ({
+        code,
+        map,
+        etag: getEtag(code, { weak: true })
+      } as TransformResult)
+
+  // Only cache the result if the module wasn't invalidated while it was
+  // being processed, so it is re-processed next time if it is stale
+  if (timestamp > mod.lastInvalidationTimestamp) {
+    if (ssr) mod.ssrTransformResult = result
+    else mod.transformResult = result
   }
+
+  return result
 }