Terminate pointer-only descriptor traversal

internal/engine/pointer_descriptor_test.go

@@ -0,0 +1,112 @@
+package engine
+
+import (
+	"context"
+	"errors"
+	"os"
+	"os/exec"
+	"reflect"
+	"testing"
+	"time"
+)
+
+type pointerOnlyLoop *pointerOnlyLoop
+
+type pointerOnlyConfig struct {
+	Loop pointerOnlyLoop `yaml:"loop"`
+}
+
+func TestPointerOnlyDescriptorsTerminate(t *testing.T) {
+	if mode := os.Getenv("CONFIGKIT_POINTER_DESCRIPTOR_TEST_MODE"); mode != "" {
+		switch mode {
+		case "decode":
+			_, err := testLoad[pointerOnlyConfig](Bytes("config.yml", []byte("loop: {}\n")))
+			var loadErr *LoadError
+			if !errors.As(err, &loadErr) {
+				t.Fatalf("load error = %v, want a safe decode failure", err)
+			}
+			for _, diagnostic := range loadErr.Diagnostics() {
+				if diagnostic.Code == CodeDecodeType && diagnostic.Path.String() == "/loop" {
+					return
+				}
+			}
+			t.Fatalf("diagnostics = %#v, want decode type at /loop", loadErr.Diagnostics())
+		case "paths":
+			schema, issue := testBuildSchema(reflect.TypeFor[pointerOnlyConfig]())
+			if issue != nil {
+				t.Fatalf("schema issue = %#v", issue)
+			}
+			if _, ok := resolveSchemaPath(schema, Keys("loop", "child")); ok {
+				t.Fatal("descendant below a pointer-only loop was accepted")
+			}
+			if _, ok := schemaSecretRoot(schema, Keys("loop", "child")); ok {
+				t.Fatal("secret path below a pointer-only loop was accepted")
+			}
+			if acceptsMapping(schema.root.fields[schema.root.fieldByName["loop"]].descriptor) {
+				t.Fatal("pointer-only loop was accepted as a mapping")
+			}
+		default:
+			t.Fatalf("unknown test mode %q", mode)
+		}
+		return
+	}
+
+	for _, mode := range []string{"decode", "paths"} {
+		t.Run(mode, func(t *testing.T) {
+			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+			defer cancel()
+			command := exec.CommandContext(ctx, os.Args[0], "-test.run=^TestPointerOnlyDescriptorsTerminate$")
+			command.Env = append(os.Environ(), "CONFIGKIT_POINTER_DESCRIPTOR_TEST_MODE="+mode)
+			output, err := command.CombinedOutput()
+			if ctx.Err() != nil {
+				t.Fatalf("pointer descriptor %s did not terminate: %s", mode, output)
+			}
+			if err != nil {
+				t.Fatalf("pointer descriptor %s failed: %v, %s", mode, err, output)
+			}
+		})
+	}
+}
+
+func TestPointerOnlyNullableFieldAndRecursiveValues(t *testing.T) {
+	for name, source := range map[string]Source{
+		"omitted": NoSource(),
+		"null":    Bytes("config.yml", []byte("loop: null\n")),
+	} {
+		t.Run(name, func(t *testing.T) {
+			result, err := testLoad[pointerOnlyConfig](source)
+			if err != nil || result.Config.Loop != nil {
+				t.Fatalf("result = %#v, error = %v", result, err)
+			}
+		})
+	}
+
+	result, err := testLoad[recursiveConfig](Bytes("config.yml", []byte("name: root\nnext:\n  name: child\n  next:\n    name: leaf\n")))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.Config.Name != "root" || result.Config.Next == nil || result.Config.Next.Name != "child" || result.Config.Next.Next == nil || result.Config.Next.Next.Name != "leaf" {
+		t.Fatalf("recursive value = %#v", result.Config)
+	}
+
+	schema, issue := testBuildSchema(reflect.TypeFor[pointerOnlyConfig]())
+	if issue != nil {
+		t.Fatal(issue.message)
+	}
+	resolved, ok := resolveSchemaPath(schema, Keys("loop"))
+	if !ok || resolved.descriptor.kind != descriptorPointer {
+		t.Fatalf("nullable pointer field resolution = %#v, %v", resolved, ok)
+	}
+
+	called := false
+	nullableResult, err := testLoad[pointerOnlyConfig](NoSource(), Options[pointerOnlyConfig]{Definition: Definition[pointerOnlyConfig]{
+		Resolve: func(config *pointerOnlyConfig, resolution *Resolution) error {
+			called = true
+			Normalize(resolution, Keys("loop"), &config.Loop, nil, "clear nullable field")
+			return nil
+		},
+	}})
+	if err != nil || !called || nullableResult.Config.Loop != nil {
+		t.Fatalf("nullable field operation = %#v, called=%v, error=%v", nullableResult, called, err)
+	}
+}