From ac6e1bf79804f0871412a79dd6a898023a57b348 Mon Sep 17 00:00:00 2001
From: unkin-agent <unkin-agent@unkin.net>
Date: Sun, 18 Oct 2026 21:16:04 +1100
Subject: [PATCH] Key goproxy merge cache on owners and cache module misses

---
 internal/virtual/goproxy_merger.go      | 34 ++++++++++++----
 internal/virtual/goproxy_merger_test.go | 54 +++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/internal/virtual/goproxy_merger.go b/internal/virtual/goproxy_merger.go
index edb83b9..f502631 100644
--- a/internal/virtual/goproxy_merger.go
+++ b/internal/virtual/goproxy_merger.go
@@ -4,7 +4,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"maps"
 	"net/http"
+	"slices"
 	"strings"
 
 	"golang.org/x/mod/module"
@@ -25,14 +27,25 @@ type GoMember struct {
 }
 
 // GoDoc is a goproxy virtual's merged @v/list for one module. Owners maps each
-// version to the first member listing it.
+// version to the first member listing it; missing caches that no member has it.
 type GoDoc struct {
-	Body   []byte
-	Owners map[string]string
-	Latest string
+	Body    []byte
+	Owners  map[string]string
+	Latest  string
+	missing bool
+}
+
+func (d *GoDoc) index() []byte {
+	if d.missing {
+		return nil
+	}
+	b := append(slices.Clone(d.Body), 0)
+	for _, v := range slices.Sorted(maps.Keys(d.Owners)) {
+		b = append(b, v+"="+d.Owners[v]+"\n"...)
+	}
+	return b
 }
 
-func (d *GoDoc) index() []byte            { return d.Body }
 func (d *GoDoc) files() map[string][]byte { return nil }
 
 // MergeGoList unions member @v/list documents, sorted by semver; the first
@@ -163,7 +176,11 @@ func (e *Engine) goList(ctx context.Context, virt models.Virtual, escMod string)
 		if err != nil {
 			return nil, err
 		}
-		return MergeGoList(members)
+		d, err := MergeGoList(members)
+		if errors.Is(err, ErrNotFound) {
+			return &GoDoc{missing: true}, nil
+		}
+		return d, err
 	})
 	if err != nil {
 		return nil, err
@@ -171,7 +188,10 @@ func (e *Engine) goList(ctx context.Context, virt models.Virtual, escMod string)
 	if inserted {
 		e.evictOldest(prefix, maxGoModules)
 	}
-	return repo.(*GoDoc), nil
+	if d := repo.(*GoDoc); !d.missing {
+		return d, nil
+	}
+	return nil, ErrNotFound
 }
 
 // goProbe returns the first member, in member order, that serves path.
diff --git a/internal/virtual/goproxy_merger_test.go b/internal/virtual/goproxy_merger_test.go
index 2796aff..0d99d19 100644
--- a/internal/virtual/goproxy_merger_test.go
+++ b/internal/virtual/goproxy_merger_test.go
@@ -7,6 +7,8 @@ import (
 	"testing"
 	"time"
 
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
@@ -117,6 +119,31 @@ func TestGoProxyRedirectsToFirstOwner(t *testing.T) {
 	if n := asked["internal example.unkin.net/!hello/@v/list"]; n != 1 {
 		t.Fatalf("merged list must be cached, internal asked %d times", n)
 	}
+	if n := asked["goproxy missing.example/mod/@v/list"]; n != 1 {
+		t.Fatalf("a module no member has must be cached, goproxy asked %d times", n)
+	}
+}
+
+func TestGoProxyFollowsOwnerChange(t *testing.T) {
+	docs := map[string]string{"internal example.com/mod/@v/list": "v0.1.0\n"}
+	e, _ := goEngine(docs, "")
+	e.mergeTTL = 0
+	zip := func() string {
+		t.Helper()
+		_, loc, err := e.GoProxy(context.Background(), goVirt(), "example.com/mod/@v/v0.1.0.zip", "")
+		if err != nil {
+			t.Fatal(err)
+		}
+		return loc
+	}
+	if loc := zip(); loc != "/api/v1/local/internal/example.com/mod/@v/v0.1.0.zip" {
+		t.Fatalf("before move: %q", loc)
+	}
+	delete(docs, "internal example.com/mod/@v/list")
+	docs["goproxy example.com/mod/@v/list"] = "v0.1.0\n"
+	if loc := zip(); loc != "/api/v1/remote/goproxy/example.com/mod/@v/v0.1.0.zip" {
+		t.Fatalf("same list, new owner: redirect still %q", loc)
+	}
 }
 
 func TestGoProxyFailsClosed(t *testing.T) {
@@ -127,3 +154,30 @@ func TestGoProxyFailsClosed(t *testing.T) {
 		}
 	}
 }
+
+func TestGoProxyLocalMemberNotFound(t *testing.T) {
+	ctx := context.Background()
+	dsn, terminate, err := testsupport.StartPostgres(ctx)
+	if err != nil {
+		t.Skip("Docker unavailable")
+	}
+	defer terminate()
+	db, err := database.New(dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	local := models.Remote{Name: "internal", PackageType: models.PackageGoProxy, RepoType: models.RepoTypeLocal}
+	if err := db.CreateRemote(ctx, &local); err != nil {
+		t.Fatal(err)
+	}
+
+	e := NewEngine(db, nil)
+	if _, err := e.fetchMemberPath(ctx, local, "example.com/mod/@latest"); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("local 404 must be ErrNotFound, got %v", err)
+	}
+	virt := models.Virtual{Name: "go", PackageType: models.PackageGoProxy, Members: []string{"internal"}}
+	if _, _, err := e.GoProxy(ctx, virt, "example.com/mod/@latest", ""); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("module only absent from a local member must be not-found, got %v", err)
+	}
+}