feat: 接入 Instance 版本与扩展可用性观测

internal/database/application/instance_service_test.go

@@ -24,6 +24,8 @@ import (
 	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
 )
 
+const serviceTestPassword = "test-only"
+
 // 延续源项目 Service 测试，用于穷举身份与装配失败；真实行为由 adapter 集成测试验证。
 type sourceStub struct {
 	credentials Credentials
@@ -35,11 +37,14 @@ func (s *sourceStub) Read(context.Context, instance.CredentialReference) (Creden
 }
 
 type databaseStub struct {
-	closes int
-	err    error
+	closes   int
+	err      error
+	metadata DatabaseMetadata
 }
 
-func (d *databaseStub) Version(context.Context) (string, error) { return "17", d.err }
+func (d *databaseStub) InspectMetadata(context.Context) (DatabaseMetadata, error) {
+	return d.metadata, d.err
+}
 func (d *databaseStub) Close() {
 	d.closes++
 }
@@ -53,7 +58,12 @@ func (c *connectorStub) Connect(context.Context, instance.Endpoint, Credentials)
 	if c.err != nil {
 		return nil, c.err
 	}
-	db := &databaseStub{}
+	db := &databaseStub{
+		metadata: DatabaseMetadata{
+			Version:             "17",
+			AvailableExtensions: []string{"plpgsql"},
+		},
+	}
 	c.databases = append(c.databases, db)
 	return db, nil
 }
@@ -98,7 +108,7 @@ func serviceTarget(t *testing.T, uid, host, secret string, generation int64) ins
 }
 
 func TestInstanceConnectionIdentity(t *testing.T) {
-	source := &sourceStub{credentials: Credentials{username: testUsername, password: "test-only"}}
+	source := &sourceStub{credentials: Credentials{username: testUsername, password: serviceTestPassword}}
 	connector := &connectorStub{}
 	service, err := NewInstanceService(source, connector)
 	if err != nil {
@@ -118,9 +128,13 @@ func TestInstanceConnectionIdentity(t *testing.T) {
 		{"same name with new UID", serviceTarget(t, "uid-2", "second", "replacement", 1), 4},
 	}
 	for _, testCase := range cases {
-		if _, err := service.ObserveVersion(ctx, testCase.target); err != nil {
+		observation, err := service.ObserveMetadata(ctx, testCase.target)
+		if err != nil {
 			t.Fatal(err)
 		}
+		if !observation.Target().Matches(testCase.target) {
+			t.Fatalf("%s: observation was bound to a previous target", testCase.name)
+		}
 		if len(connector.databases) != testCase.wantConnections {
 			t.Fatalf("%s: got %d connections, want %d", testCase.name, len(connector.databases), testCase.wantConnections)
 		}
@@ -137,11 +151,64 @@ func TestInstanceConnectionIdentity(t *testing.T) {
 	}
 }
 
+func TestMetadataObservationFreshnessAndFailure(t *testing.T) {
+	source := &sourceStub{credentials: Credentials{username: testUsername, password: serviceTestPassword}}
+	connector := &connectorStub{}
+	service, err := NewInstanceService(source, connector)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer service.Close()
+	ctx := context.Background()
+	target := serviceTarget(t, "metadata-uid", "first", "admin", 1)
+	observed, err := service.ObserveMetadata(ctx, target)
+	if err != nil || observed.Version() != "17" || !observed.Target().Matches(target) {
+		t.Fatalf("metadata observation: %v", err)
+	}
+	requested := instance.NewExtensionSet([]string{"plpgsql"})
+	if observed.Extensions().Check(requested).Decision != instance.ExtensionsAccepted {
+		t.Fatal("extension list was not observed")
+	}
+
+	// 连接可以复用，但每轮必须重新查询；旧观察还必须与 adapter 的可变 slice 脱离。
+	database := connector.databases[0]
+	database.metadata.AvailableExtensions[0] = "replacement"
+	if observed.Extensions().Check(requested).Decision != instance.ExtensionsAccepted {
+		t.Fatal("adapter mutation changed a completed observation")
+	}
+	refreshed, err := service.ObserveMetadata(ctx, target)
+	if err != nil || refreshed.Extensions().Check(requested).Decision != instance.ExtensionsUnsupported {
+		t.Fatalf("extension list was cached across observations: %v", err)
+	}
+	database.metadata.AvailableExtensions = nil
+	empty, err := service.ObserveMetadata(ctx, target)
+	if err != nil || empty.Extensions().Check(requested).Decision != instance.ExtensionsUnsupported {
+		t.Fatalf("successful empty list was treated as unobserved: %v", err)
+	}
+
+	// 即使 adapter 附带部分数据，错误仍使整个观察失效。
+	database.err = ErrObservation
+	failed, err := service.ObserveMetadata(ctx, target)
+	if !errors.Is(err, ErrObservation) || failed.Version() != "" || failed.Target().Validate() == nil {
+		t.Fatal("failed query returned a bound observation")
+	}
+	if failed.Extensions().Check(requested).Decision != instance.ExtensionSupportUnobserved {
+		t.Fatal("failed query was interpreted as an empty extension list")
+	}
+	if _, err := service.ObserveMetadata(ctx, target); err != nil {
+		t.Fatalf("retry after query failure: %v", err)
+	}
+	connector.databases[1].metadata.Version = ""
+	if _, err := service.ObserveMetadata(ctx, target); !errors.Is(err, ErrObservation) {
+		t.Fatal("missing server version was accepted as complete metadata")
+	}
+}
+
 func TestInstanceAssemblyFailureRecovery(t *testing.T) {
 	ctx := context.Background()
 	target := serviceTarget(t, "uid-1", "first", "admin", 1)
 	source := &sourceStub{
-		credentials: Credentials{username: testUsername, password: "test-only"},
+		credentials: Credentials{username: testUsername, password: serviceTestPassword},
 		err:         errors.New("unsafe source error"),
 	}
 	connector := &connectorStub{err: ErrConnection}