internal/pkg: discontinue DCE resolution on signal

This serves as a stopgap measure to skip long-running DCE resolutions.

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

internal/pkg/pkg.go

@@ -15,6 +15,7 @@ import (
 	"io/fs"
 	"maps"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"runtime"
 	"slices"
@@ -1500,16 +1501,21 @@ 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(ir, me)
+			_e.unwrapM(ctx, ir, me)
 			continue
 		}
 		me[id] = err
@@ -1517,9 +1523,12 @@ func (e *DependencyCureError) unwrapM(
 }
 
 // unwrap recursively expands and deduplicates underlying errors.
-func (e *DependencyCureError) unwrap(ir *IRCache) DependencyCureError {
+func (e *DependencyCureError) unwrap(
+	ctx context.Context,
+	ir *IRCache,
+) DependencyCureError {
 	me := make(map[unique.Handle[ID]]*CureError)
-	e.unwrapM(ir, me)
+	e.unwrapM(ctx, ir, me)
 	type ent struct {
 		id  unique.Handle[ID]
 		err *CureError
@@ -1544,7 +1553,10 @@ func (e *DependencyCureError) unwrap(ir *IRCache) DependencyCureError {
 
 // Unwrap returns a deduplicated slice of underlying errors.
 func (e *DependencyCureError) Unwrap() []error {
-	errs := e.unwrap(NewIR())
+	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
@@ -1554,8 +1566,11 @@ func (e *DependencyCureError) Unwrap() []error {
 
 // 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(ir)
+	errs := e.unwrap(ctx, ir)
 	if len(errs) == 0 {
 		return "invalid dependency cure outcome"
 	}
@@ -1566,6 +1581,9 @@ func (e *DependencyCureError) Error() string {
 			reportName(err.A, ir.Ident(err.A)) + ": " +
 			err.Error())
 	}
+	if ctx.Err() != nil {
+		buf.WriteString("\nerror resolution cancelled")
+	}
 	return buf.String()
 }