internal/pkg: flush cached errors on abort

This avoids disabling the artifact until cache is reopened. The same has to be implemented for Cancel in a future change.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg.go

@@ -219,7 +219,7 @@ func (c *common) Open(a Artifact) (r io.ReadCloser, err error) {
 	}
 
 	var pathname *check.Absolute
-	if pathname, _, err = c.cache.Cure(a); err != nil {
+	if pathname, _, err = c.cache.cure(a, true); err != nil {
 		return
 	}
 
@@ -601,6 +601,8 @@ type Cache struct {
 	identPending map[unique.Handle[ID]]*pendingCure
 	// Synchronises access to ident and corresponding filesystem entries.
 	identMu sync.RWMutex
+	// Synchronises entry into Abort and Cure.
+	abortMu sync.RWMutex
 
 	// Synchronises entry into exclusive artifacts for the cure method.
 	exclMu sync.Mutex
@@ -1036,6 +1038,9 @@ func (c *Cache) Scrub(checks int) error {
 // loadOrStoreIdent attempts to load a cached [Artifact] by its identifier or
 // wait for a pending [Artifact] to cure. If neither is possible, the current
 // identifier is stored in identPending and a non-nil channel is returned.
+//
+// Since identErr is treated as grow-only, loadOrStoreIdent must not be entered
+// without holding a read lock on abortMu.
 func (c *Cache) loadOrStoreIdent(id unique.Handle[ID]) (
 	ctx context.Context,
 	done chan<- struct{},
@@ -1069,6 +1074,7 @@ func (c *Cache) loadOrStoreIdent(id unique.Handle[ID]) (
 	d := make(chan struct{})
 	pending = &pendingCure{done: d}
 	ctx, pending.cancel = context.WithCancel(c.toplevel.Load().ctx)
+	c.wg.Add(1)
 	c.identPending[id] = pending
 	c.identMu.Unlock()
 	done = d
@@ -1091,6 +1097,7 @@ func (c *Cache) finaliseIdent(
 	}
 	delete(c.identPending, id)
 	c.identMu.Unlock()
+	c.wg.Done()
 
 	close(done)
 }
@@ -1310,6 +1317,9 @@ func (c *Cache) Cure(a Artifact) (
 	checksum unique.Handle[Checksum],
 	err error,
 ) {
+	c.abortMu.RLock()
+	defer c.abortMu.RUnlock()
+
 	if err = c.toplevel.Load().ctx.Err(); err != nil {
 		return
 	}
@@ -1504,7 +1514,8 @@ func (r *RContext) NewMeasuredReader(
 	return r.cache.newMeasuredReader(rc, checksum)
 }
 
-// cure implements Cure without checking the full dependency graph.
+// cure implements Cure without acquiring a read lock on abortMu. cure must not
+// be entered during Abort.
 func (c *Cache) cure(a Artifact, curesExempt bool) (
 	pathname *check.Absolute,
 	checksum unique.Handle[Checksum],
@@ -1871,8 +1882,8 @@ func (c *Cache) OpenStatus(a Artifact) (r io.ReadSeekCloser, err error) {
 	return
 }
 
-// Abort cancels all pending cures but does not close the store. Abort does not
-// wait for cures to complete.
+// Abort cancels all pending cures and waits for them to clean up, but does not
+// close the cache.
 func (c *Cache) Abort() {
 	c.closeMu.Lock()
 	defer c.closeMu.Unlock()
@@ -1881,7 +1892,16 @@ func (c *Cache) Abort() {
 		return
 	}
 
-	c.toplevel.Swap(newToplevel(c.parent)).cancel()
+	c.toplevel.Load().cancel()
+	c.abortMu.Lock()
+	defer c.abortMu.Unlock()
+
+	// holding abortMu, identPending stays empty
+	c.wg.Wait()
+	c.identMu.Lock()
+	c.toplevel.Store(newToplevel(c.parent))
+	clear(c.identErr)
+	c.identMu.Unlock()
 }
 
 // Close cancels all pending cures and waits for them to clean up.