internal/pkg: collection helper-artifact

This was moved from internal/rosa because it is considered generally useful.

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

internal/pkg/pkg.go

@@ -366,7 +366,7 @@ type TrivialArtifact interface {
 }
 
 // KnownIdent is optionally implemented by [Artifact] and is used instead of
-// [Kind.Ident] when it is available.
+// [Cache.Ident] when it is available.
 //
 // This is very subtle to use correctly. The implementation must ensure that
 // this value is globally unique, otherwise [Cache] can enter an inconsistent
@@ -439,6 +439,11 @@ const (
 	KindCustomOffset = 1 << 31
 )
 
+const (
+	// kindCollection is the kind of [Collect]. It never cures successfully.
+	kindCollection Kind = KindCustomOffset - 1 - iota
+)
+
 const (
 	// fileLock is the file name appended to Cache.base for guaranteeing
 	// exclusive access to the cache directory.
@@ -1890,3 +1895,33 @@ func open(
 
 	return &c, nil
 }
+
+// Collected is returned by [Collect.Cure] to indicate a successful collection.
+type Collected struct{}
+
+// Error returns a constant string to satisfy error, but should never be seen
+// by the user.
+func (Collected) Error() string { return "artifacts successfully collected" }
+
+// IsCollected returns whether the underlying error contains that of the result
+// of curing a [Collect] helper.
+func IsCollected(err error) bool { return errors.As(err, new(Collected)) }
+
+// Collect implements [pkg.FloodArtifact] to concurrently cure multiple
+// [pkg.Artifact]. It returns [Collected].
+type Collect []Artifact
+
+// Cure returns [Collected].
+func (*Collect) Cure(*FContext) error { return Collected{} }
+
+// Kind returns the hardcoded [pkg.Kind] value.
+func (*Collect) Kind() Kind { return kindCollection }
+
+// Params is a noop: dependencies are already represented in the header.
+func (*Collect) Params(*IContext) {}
+
+// Dependencies returns [Collect] as is.
+func (c *Collect) Dependencies() []Artifact { return *c }
+
+// IsExclusive returns false: Cure is a noop.
+func (*Collect) IsExclusive() bool { return false }

internal/rosa/rosa.go

@@ -20,9 +20,6 @@ const (
 
 	// kindBusyboxBin is the kind of [pkg.Artifact] of busyboxBin.
 	kindBusyboxBin
-
-	// kindCollection is the kind of [Collect]. It never cures successfully.
-	kindCollection
 )
 
 // mustDecode is like [pkg.MustDecode], but replaces the zero value and prints
@@ -591,29 +588,3 @@ cd '/usr/src/` + name + `/'
 		})...,
 	)
 }
-
-// Collected is returned by [Collect.Cure] to indicate a successful collection.
-type Collected struct{}
-
-// Error returns a constant string to satisfy error, but should never be seen
-// by the user.
-func (Collected) Error() string { return "artifacts successfully collected" }
-
-// Collect implements [pkg.FloodArtifact] to concurrently cure multiple
-// [pkg.Artifact]. It returns [Collected].
-type Collect []pkg.Artifact
-
-// Cure returns [Collected].
-func (*Collect) Cure(*pkg.FContext) error { return Collected{} }
-
-// Kind returns the hardcoded [pkg.Kind] value.
-func (*Collect) Kind() pkg.Kind { return kindCollection }
-
-// Params does not write anything, dependencies are already represented in the header.
-func (*Collect) Params(*pkg.IContext) {}
-
-// Dependencies returns [Collect] as is.
-func (c *Collect) Dependencies() []pkg.Artifact { return *c }
-
-// IsExclusive returns false: Cure is a noop.
-func (*Collect) IsExclusive() bool { return false }