internal/pkg: in-flight error resolution

The DCE is a slow and overcomplicated solution to a simple problem. This change replaces the DCE by resolving errors in-flight.

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

internal/pkg/pkg.go

@@ -18,7 +18,6 @@ import (
 	"maps"
 	"math"
 	"os"
-	"os/signal"
 	"path/filepath"
 	"runtime"
 	"slices"
@@ -654,10 +653,10 @@ type pendingArtifactDep struct {
 	// if curing succeeds.
 	resP *cureRes
 
-	// Address of result error slice populated during [Cache.Cure], dereferenced
+	// Address of result error map populated during [Cache.Cure], dereferenced
 	// after acquiring errsMu if curing fails. No additional action is taken,
 	// [Cache] and its caller are responsible for further error handling.
-	errs *DependencyCureError
+	errs InputError
 	// Address of mutex synchronising access to errs.
 	errsMu *sync.Mutex
 
@@ -1721,109 +1720,43 @@ retry:
 	goto retry
 }
 
-// CureError wraps a non-nil error returned attempting to cure an [Artifact].
-type CureError struct {
-	A   Artifact
-	Err error
-}
+// An InputError describes inputs of a [FloodArtifact] which had failed to cure.
+type InputError map[Artifact]error
 
-// Unwrap returns the underlying error.
-func (e *CureError) Unwrap() error { return e.Err }
+// Error returns a user-facing, deterministic text representation of e.
+func (e InputError) Error() string {
+	ir := NewIR()
 
-// Error returns the error message from the underlying Err.
-func (e *CureError) Error() string { return e.Err.Error() }
-
-// A DependencyCureError wraps errors returned while curing dependencies.
-type DependencyCureError []*CureError
-
-// unwrapM recursively expands underlying errors into a caller-supplied map.
-func (e *DependencyCureError) unwrapM(
-	ctx context.Context,
-	ir *IRCache,
-	me map[unique.Handle[ID]]*CureError,
-) {
-	for _, err := range *e {
-		if ctx.Err() != nil {
-			break
-		}
-
-		id := ir.Ident(err.A)
-		if _, ok := me[id]; ok {
-			continue
-		}
-		if _e, ok := err.Err.(*DependencyCureError); ok {
-			_e.unwrapM(ctx, ir, me)
-			continue
-		}
-		me[id] = err
+	type input struct {
+		a  Artifact
+		id unique.Handle[ID]
 	}
-}
-
-// unwrap recursively expands and deduplicates underlying errors.
-func (e *DependencyCureError) unwrap(
-	ctx context.Context,
-	ir *IRCache,
-) DependencyCureError {
-	me := make(map[unique.Handle[ID]]*CureError)
-	e.unwrapM(ctx, ir, me)
-	type ent struct {
-		id  unique.Handle[ID]
-		err *CureError
-	}
-	errs := make([]*ent, 0, len(me))
-	for id, err := range me {
-		errs = append(errs, &ent{id, err})
+	p := make([]input, 0, len(e))
+	for a := range e {
+		p = append(p, input{a, ir.Ident(a)})
 	}
 
 	var identBuf [2]ID
-	slices.SortFunc(errs, func(a, b *ent) int {
+	slices.SortFunc(p, func(a, b input) int {
 		identBuf[0], identBuf[1] = a.id.Value(), b.id.Value()
 		return slices.Compare(identBuf[0][:], identBuf[1][:])
 	})
 
-	_errs := make(DependencyCureError, len(errs))
-	for i, v := range errs {
-		_errs[i] = v.err
-	}
-	return _errs
-}
-
-// Unwrap returns a deduplicated slice of underlying errors.
-func (e *DependencyCureError) Unwrap() []error {
-	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
-	defer cancel()
-
-	errs := e.unwrap(ctx, NewIR())
-	_errs := make([]error, len(errs))
-	for i, err := range errs {
-		_errs[i] = err
-	}
-	return _errs
-}
-
-// Error returns a user-facing multiline error message.
-func (e *DependencyCureError) Error() string {
-	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
-	defer cancel()
-
-	ir := NewIR()
-	errs := e.unwrap(ctx, ir)
-	if len(errs) == 0 {
-		return "invalid dependency cure outcome"
-	}
 	var buf strings.Builder
-	buf.WriteString("errors curing dependencies:")
-	for _, err := range errs {
+	buf.WriteString("errors curing inputs:")
+	for _, i := range p {
 		buf.WriteString("\n\t" +
-			reportName(err.A, ir.Ident(err.A)) + ": " +
-			err.Error())
-	}
-	if ctx.Err() != nil {
-		buf.WriteString("\nerror resolution cancelled")
+			reportName(i.a, i.id) + ": " +
+			e[i.a].Error())
 	}
 	return buf.String()
 }
 
+// Unwrap returns a slice of underlying errors in unspecified order.
+func (e InputError) Unwrap() []error {
+	return slices.AppendSeq(make([]error, 0, len(e)), maps.Values(e))
+}
+
 // enterCure must be called before entering an [Artifact] implementation.
 func (c *Cache) enterCure(a Artifact, curesExempt bool) error {
 	if c.attr.Notify != nil {
@@ -2023,7 +1956,7 @@ func (c *Cache) cureMany(
 	wg.Add(len(inputs))
 	var mask []bool
 	res := make([]cureRes, len(inputs))
-	errs := make(DependencyCureError, 0, len(inputs))
+	errs := make(InputError)
 	var errsMu sync.Mutex
 	if shallow {
 		mask = make([]bool, len(inputs))
@@ -2042,13 +1975,13 @@ func (c *Cache) cureMany(
 				continue
 			}
 		}
-		pending := pendingArtifactDep{d, &res[i], &errs, &errsMu, &wg}
+		pending := pendingArtifactDep{d, &res[i], errs, &errsMu, &wg}
 		go pending.cure(c)
 	}
 	wg.Wait()
 
 	if len(errs) > 0 {
-		return mask, &errs
+		return mask, errs
 	}
 	for i, p := range res {
 		if shallow && mask[i] {
@@ -2651,7 +2584,11 @@ func (pending *pendingArtifactDep) cure(c *Cache) {
 	}
 
 	pending.errsMu.Lock()
-	*pending.errs = append(*pending.errs, &CureError{pending.a, err})
+	if errs, ok := err.(InputError); ok {
+		maps.Copy(pending.errs, errs)
+	} else {
+		pending.errs[pending.a] = err
+	}
 	pending.errsMu.Unlock()
 }