internal/pkg: pass impure job count

This is cleaner than checking cpu count during cure, it is impossible to avoid impurity in both situations but this is configurable.

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

cmd/mbf/main.go

@@ -72,6 +72,7 @@ func main() {
 	var (
 		flagQuiet bool
 		flagCures int
+		flagJobs  int
 		flagBase  string
 		flagIdle  bool
 
@@ -99,7 +100,7 @@ func main() {
 		if flagHostAbstract {
 			flags |= pkg.CHostAbstract
 		}
-		cache, err = pkg.Open(ctx, msg, flags, flagCures, base)
+		cache, err = pkg.Open(ctx, msg, flags, flagCures, flagJobs, base)
 
 		return
 	}).Flag(
@@ -110,6 +111,10 @@ func main() {
 		&flagCures,
 		"cures", command.IntFlag(0),
 		"Maximum number of dependencies to cure at any given time",
+	).Flag(
+		&flagJobs,
+		"jobs", command.IntFlag(0),
+		"Preferred number of jobs to run, when applicable",
 	).Flag(
 		&flagBase,
 		"d", command.StringFlag("$MBF_CACHE_DIR"),

internal/pkg/pkg.go

@@ -188,6 +188,10 @@ func (c *common) Unwrap() context.Context { return c.cache.ctx }
 // GetMessage returns [message.Msg] held by the underlying [Cache].
 func (c *common) GetMessage() message.Msg { return c.cache.msg }
 
+// GetJobs returns the preferred number of jobs to run, when applicable. Its
+// value must not affect cure outcome.
+func (c *common) GetJobs() int { return c.cache.jobs }
+
 // GetWorkDir returns a pathname to a directory which [Artifact] is expected to
 // write its output to. This is not the final resting place of the [Artifact]
 // and this pathname should not be directly referred to in the final contents.
@@ -552,6 +556,8 @@ type Cache struct {
 	base *check.Absolute
 	// Immutable cure options set by [Open].
 	flags int
+	// Immutable job count, when applicable.
+	jobs int
 
 	// Artifact to [unique.Handle] of identifier cache.
 	artifact sync.Map
@@ -1818,7 +1824,7 @@ func (c *Cache) Close() {
 // caller-supplied value, however direct calls to [Cache.Cure] is not subject
 // to this limitation.
 //
-// A cures value of 0 or lower is equivalent to the value returned by
+// A cures or jobs value of 0 or lower is equivalent to the value returned by
 // [runtime.NumCPU].
 //
 // A successful call to Open guarantees exclusive access to the on-filesystem
@@ -1828,10 +1834,10 @@ func (c *Cache) Close() {
 func Open(
 	ctx context.Context,
 	msg message.Msg,
-	flags, cures int,
+	flags, cures, jobs int,
 	base *check.Absolute,
 ) (*Cache, error) {
-	return open(ctx, msg, flags, cures, base, true)
+	return open(ctx, msg, flags, cures, jobs, base, true)
 }
 
 // open implements Open but allows omitting the [lockedfile] lock when called
@@ -1839,13 +1845,16 @@ func Open(
 func open(
 	ctx context.Context,
 	msg message.Msg,
-	flags, cures int,
+	flags, cures, jobs int,
 	base *check.Absolute,
 	lock bool,
 ) (*Cache, error) {
 	if cures < 1 {
 		cures = runtime.NumCPU()
 	}
+	if jobs < 1 {
+		jobs = runtime.NumCPU()
+	}
 
 	for _, name := range []string{
 		dirIdentifier,
@@ -1862,6 +1871,7 @@ func open(
 	c := Cache{
 		cures: make(chan struct{}, cures),
 		flags: flags,
+		jobs:  jobs,
 
 		msg:  msg,
 		base: base,

internal/pkg/pkg_test.go

@@ -35,7 +35,7 @@ import (
 func unsafeOpen(
 	ctx context.Context,
 	msg message.Msg,
-	flags, cures int,
+	flags, cures, jobs int,
 	base *check.Absolute,
 	lock bool,
 ) (*pkg.Cache, error)
@@ -230,7 +230,7 @@ func TestIdent(t *testing.T) {
 	var cache *pkg.Cache
 	if a, err := check.NewAbs(t.TempDir()); err != nil {
 		t.Fatal(err)
-	} else if cache, err = pkg.Open(t.Context(), msg, 0, 0, a); err != nil {
+	} else if cache, err = pkg.Open(t.Context(), msg, 0, 0, 0, a); err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(cache.Close)
@@ -304,7 +304,7 @@ func checkWithCache(t *testing.T, testCases []cacheTestCase) {
 			}
 
 			var scrubFunc func() error // scrub after hashing
-			if c, err := pkg.Open(t.Context(), msg, flags, 1<<4, base); err != nil {
+			if c, err := pkg.Open(t.Context(), msg, flags, 1<<4, 0, base); err != nil {
 				t.Fatalf("Open: error = %v", err)
 			} else {
 				t.Cleanup(c.Close)
@@ -606,7 +606,7 @@ func TestCache(t *testing.T) {
 			if c0, err := unsafeOpen(
 				t.Context(),
 				message.New(nil),
-				0, 0, base, false,
+				0, 0, 0, base, false,
 			); err != nil {
 				t.Fatalf("open: error = %v", err)
 			} else {
@@ -1263,7 +1263,7 @@ func TestNew(t *testing.T) {
 		if _, err := pkg.Open(
 			t.Context(),
 			message.New(nil),
-			0, 0, check.MustAbs(container.Nonexistent),
+			0, 0, 0, check.MustAbs(container.Nonexistent),
 		); !reflect.DeepEqual(err, wantErr) {
 			t.Errorf("Open: error = %#v, want %#v", err, wantErr)
 		}
@@ -1291,7 +1291,7 @@ func TestNew(t *testing.T) {
 		if _, err := pkg.Open(
 			t.Context(),
 			message.New(nil),
-			0, 0, tempDir.Append("cache"),
+			0, 0, 0, tempDir.Append("cache"),
 		); !reflect.DeepEqual(err, wantErr) {
 			t.Errorf("Open: error = %#v, want %#v", err, wantErr)
 		}

internal/rosa/rosa_test.go

@@ -60,7 +60,7 @@ func getCache(t *testing.T) *pkg.Cache {
 			msg := message.New(log.New(os.Stderr, "rosa: ", 0))
 			msg.SwapVerbose(true)
 
-			if buildTestCache, err = pkg.Open(ctx, msg, 0, 0, a); err != nil {
+			if buildTestCache, err = pkg.Open(ctx, msg, 0, 0, 0, a); err != nil {
 				t.Fatal(err)
 			}
 		}