internal/pkg: cache flags

This is cleaner for extending the API.

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

internal/pkg/pkg.go

@@ -13,7 +13,6 @@ import (
 	"hash"
 	"io"
 	"io/fs"
-	"iter"
 	"maps"
 	"os"
 	"path/filepath"
@@ -331,23 +330,6 @@ type FloodArtifact interface {
 	Artifact
 }
 
-// Flood returns an iterator over the dependency tree of an [Artifact].
-func Flood(a Artifact) iter.Seq[Artifact] {
-	return func(yield func(Artifact) bool) {
-		for _, d := range a.Dependencies() {
-			if !yield(d) {
-				return
-			}
-
-			for d0 := range Flood(d) {
-				if !yield(d0) {
-					return
-				}
-			}
-		}
-	}
-}
-
 // TrivialArtifact refers to an [Artifact] that cures without requiring that
 // any other [Artifact] is cured before it. Its dependency tree is ignored after
 // computing its identifier.
@@ -506,6 +488,23 @@ type pendingArtifactDep struct {
 	*sync.WaitGroup
 }
 
+const (
+	// CValidateKnown causes [KnownChecksum] outcomes to be validated to match
+	// its intended checksum.
+	//
+	// A correct implementation of [KnownChecksum] does not successfully cure
+	// with output not matching its intended checksum. When an implementation
+	// fails to perform this validation correctly, the on-disk format enters
+	// an inconsistent state (correctable by [Cache.Scrub]).
+	//
+	// This flag causes [Cache.Cure] to always compute the checksum, and reject
+	// a cure if it does not match the intended checksum.
+	//
+	// This behaviour significantly reduces performance and is not recommended
+	// outside of testing a custom [Artifact] implementation.
+	CValidateKnown = 1 << iota
+)
+
 // Cache is a support layer that implementations of [Artifact] can use to store
 // cured [Artifact] data in a content addressed fashion.
 type Cache struct {
@@ -525,12 +524,8 @@ type Cache struct {
 
 	// Directory where all [Cache] related files are placed.
 	base *check.Absolute
-
-	// Whether to validate [FileArtifact.Cure] for a [KnownChecksum] file. This
-	// significantly reduces performance.
-	strict bool
-	// Maximum size of a dependency graph.
-	threshold uintptr
+	// Immutable cure options set by [Open].
+	flags int
 
 	// Artifact to [unique.Handle] of identifier cache.
 	artifact sync.Map
@@ -563,22 +558,6 @@ type Cache struct {
 	inExec atomic.Bool
 }
 
-// IsStrict returns whether the [Cache] strictly verifies checksums.
-func (c *Cache) IsStrict() bool { return c.strict }
-
-// SetStrict sets whether the [Cache] strictly verifies checksums, even when
-// the implementation promises to validate them internally. This significantly
-// reduces performance and is not recommended outside of testing.
-//
-// This method is not safe for concurrent use with any other method.
-func (c *Cache) SetStrict(strict bool) { c.strict = strict }
-
-// SetThreshold imposes a maximum size on the dependency graph, checked on every
-// call to Cure. The zero value disables this check entirely.
-//
-// This method is not safe for concurrent use with any other method.
-func (c *Cache) SetThreshold(threshold uintptr) { c.threshold = threshold }
-
 // extIdent is a [Kind] concatenated with [ID].
 type extIdent [wordSize + len(ID{})]byte
 
@@ -1229,14 +1208,6 @@ func (e InvalidArtifactError) Error() string {
 	return "artifact " + Encode(e) + " cannot be cured"
 }
 
-// DependencyError refers to an artifact with a dependency tree larger than the
-// threshold specified by a previous call to [Cache.SetThreshold].
-type DependencyError struct{ A Artifact }
-
-func (e DependencyError) Error() string {
-	return "artifact has too many dependencies"
-}
-
 // Cure cures the [Artifact] and returns its pathname and [Checksum]. Direct
 // calls to Cure are not subject to the cures limit.
 func (c *Cache) Cure(a Artifact) (
@@ -1252,18 +1223,6 @@ func (c *Cache) Cure(a Artifact) (
 	default:
 	}
 
-	if c.threshold > 0 {
-		var n uintptr
-		for range Flood(a) {
-			if n == c.threshold {
-				err = DependencyError{a}
-				return
-			}
-			n++
-		}
-		c.msg.Verbosef("visited %d artifacts", n)
-	}
-
 	return c.cure(a, true)
 }
 
@@ -1586,7 +1545,7 @@ func (c *Cache) cure(a Artifact, curesExempt bool) (
 		}
 		r, err = f.Cure(&RContext{common{c}})
 		if err == nil {
-			if checksumPathname == nil || c.IsStrict() {
+			if checksumPathname == nil || c.flags&CValidateKnown != 0 {
 				h := sha512.New384()
 				hbw := c.getWriter(h)
 				_, err = io.Copy(w, io.TeeReader(r, hbw))
@@ -1603,7 +1562,7 @@ func (c *Cache) cure(a Artifact, curesExempt bool) (
 					if checksumPathname == nil {
 						checksum = unique.Make(Checksum(buf[:]))
 						checksums = Encode(Checksum(buf[:]))
-					} else if c.IsStrict() {
+					} else if c.flags&CValidateKnown != 0 {
 						if got := Checksum(buf[:]); got != checksum.Value() {
 							err = &ChecksumMismatchError{
 								Got:  got,
@@ -1841,10 +1800,10 @@ func (c *Cache) Close() {
 func Open(
 	ctx context.Context,
 	msg message.Msg,
-	cures int,
+	flags, cures int,
 	base *check.Absolute,
 ) (*Cache, error) {
-	return open(ctx, msg, cures, base, true)
+	return open(ctx, msg, flags, cures, base, true)
 }
 
 // open implements Open but allows omitting the [lockedfile] lock when called
@@ -1852,7 +1811,7 @@ func Open(
 func open(
 	ctx context.Context,
 	msg message.Msg,
-	cures int,
+	flags, cures int,
 	base *check.Absolute,
 	lock bool,
 ) (*Cache, error) {
@@ -1874,6 +1833,7 @@ func open(
 
 	c := Cache{
 		cures: make(chan struct{}, cures),
+		flags: flags,
 
 		msg:  msg,
 		base: base,