Provide the current visitor location as a path string

dispatchrun · Jul 9, 2024 · 2de08bd · 2de08bd
1 parent b24f1d4
commit 2de08bd
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Showing 2 changed files with 168 additions and 27 deletions.
diff --git a/internal/reflectext/visitor.go b/internal/reflectext/visitor.go
@@ -3,6 +3,8 @@ package reflectext
 import (
 	"fmt"
 	"reflect"
+	"slices"
+	"strings"
 )
 
 // Visitor visits values in a reflect.Value graph.
@@ -136,6 +138,7 @@ func (flags VisitorFlags) Has(flag VisitorFlags) bool {
 // VisitorContext is Visitor context.
 type VisitorContext struct {
 	parent *VisitorContext
+	path   []pathSegment
 	impl   Visitor
 	flags  VisitorFlags
 }
@@ -153,7 +156,7 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 
 	// Special case for reflect.Value.
 	if ctx.flags.Has(VisitReflectValues) && v.Type() == ReflectValueType {
-		ctx.Visit(v.Interface().(reflect.Value))
+		ctx.WithReflectValue(v).Visit(v.Interface().(reflect.Value))
 		return
 	}
 
@@ -185,7 +188,7 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 
 	case reflect.Pointer:
 		if visitor.VisitPointer(ctx, v) && !v.IsNil() {
-			ctx.Visit(v.Elem())
+			ctx.WithPointer(v).Visit(v.Elem())
 		}
 
 	case reflect.UnsafePointer:
@@ -194,7 +197,7 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 	case reflect.Array:
 		if visitor.VisitArray(ctx, v) {
 			for i := 0; i < v.Len(); i++ {
-				ctx.Visit(v.Index(i))
+				ctx.WithArrayIndex(v, i).Visit(v.Index(i))
 			}
 		}
 
@@ -204,16 +207,18 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 				v = MakeSlice(v.Type(), v.UnsafePointer(), v.Cap(), v.Cap())
 			}
 			for i := 0; i < v.Len(); i++ {
-				ctx.Visit(v.Index(i))
+				ctx.WithSliceIndex(v, i).Visit(v.Index(i))
 			}
 		}
 
 	case reflect.Map:
 		if visitor.VisitMap(ctx, v) && !v.IsNil() {
 			iter := v.MapRange()
 			for iter.Next() {
-				ctx.Visit(iter.Key())
-				ctx.Visit(iter.Value())
+				key := iter.Key()
+				val := iter.Value()
+				ctx.WithMapKey(v, key).Visit(key)
+				ctx.WithMapValue(v, key).Visit(val)
 			}
 		}
 
@@ -223,16 +228,16 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 
 	case reflect.Struct:
 		if visitor.VisitStruct(ctx, v) {
+			t := v.Type()
 			if ctx.flags.Has(VisitUnexportedFields) {
 				unrestricted := StructValueOf(v)
 				for i := 0; i < unrestricted.NumField(); i++ {
-					ctx.Visit(unrestricted.Field(i))
+					ctx.WithStructField(v, t.Field(i)).Visit(unrestricted.Field(i))
 				}
 			} else {
-				t := v.Type()
 				for i := 0; i < v.NumField(); i++ {
 					if ft := t.Field(i); ft.IsExported() {
-						ctx.Visit(v.Field(i))
+						ctx.WithStructField(v, t.Field(i)).Visit(v.Field(i))
 					}
 				}
 			}
@@ -241,20 +246,34 @@ func (ctx VisitorContext) Visit(v reflect.Value) {
 	case reflect.Func:
 		if visitor.VisitFunc(ctx, v) && !v.IsNil() && ctx.flags.Has(VisitClosures) {
 			if closure, ok := FuncValueOf(v).Closure(); ok {
-				ctx.Visit(closure)
+				ctx.WithClosure(v).Visit(closure)
 			}
 		}
 
 	case reflect.Interface:
 		if visitor.VisitInterface(ctx, v) && !v.IsNil() {
-			ctx.Visit(v.Elem())
+			ctx.WithInterface(v).Visit(v.Elem())
 		}
 
 	default:
 		panic("unreachable")
 	}
 }
 
+// Path returns a string that represents the location in the
+// reflect.Value graph.
+func (ctx VisitorContext) Path() string {
+	var b strings.Builder
+	for _, s := range ctx.path {
+		b.WriteString(s.String())
+	}
+	parent := "$"
+	if ctx.parent != nil {
+		parent = ctx.parent.Path()
+	}
+	return parent + b.String()
+}
+
 // Fork creates a new Visitor context, linked to the current
 // context and its location.
 func (ctx VisitorContext) Fork(impl Visitor) VisitorContext {
@@ -265,6 +284,125 @@ func (ctx VisitorContext) Fork(impl Visitor) VisitorContext {
 	}
 }
 
+func (ctx VisitorContext) withPathSegment(s pathSegment) VisitorContext {
+	c := ctx // shallow copy
+	c.path = append(slices.Clip(c.path), s)
+	return c
+}
+
+func (ctx VisitorContext) WithArrayIndex(a reflect.Value, i int) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: indexType,
+		val: a,
+		idx: i,
+	})
+}
+
+func (ctx VisitorContext) WithSliceIndex(s reflect.Value, i int) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: indexType,
+		val: s,
+		idx: i,
+	})
+}
+
+func (ctx VisitorContext) WithStructField(s reflect.Value, f reflect.StructField) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ:   structType,
+		val:   s,
+		field: f,
+	})
+}
+
+func (ctx VisitorContext) WithMapKey(m, k reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ:  mapKeyType,
+		val:  m,
+		elem: k,
+	})
+}
+
+func (ctx VisitorContext) WithMapValue(m, k reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ:  mapValType,
+		val:  m,
+		elem: k,
+	})
+}
+
+func (ctx VisitorContext) WithClosure(f reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: closureType,
+		val: f,
+	})
+}
+
+func (ctx VisitorContext) WithInterface(i reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: interfaceType,
+		val: i,
+	})
+}
+
+func (ctx VisitorContext) WithPointer(p reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: pointerType,
+		val: p,
+	})
+}
+
+func (ctx VisitorContext) WithReflectValue(v reflect.Value) VisitorContext {
+	return ctx.withPathSegment(pathSegment{
+		typ: reflectType,
+		val: v,
+	})
+}
+
+type pathSegment struct {
+	typ  segmentType
+	val  reflect.Value
+	elem reflect.Value
+
+	field reflect.StructField
+	idx   int
+}
+
+type segmentType int
+
+const (
+	indexType segmentType = iota
+	structType
+	mapKeyType
+	mapValType
+	closureType
+	interfaceType
+	pointerType
+	reflectType
+)
+
+func (s pathSegment) String() string {
+	switch s.typ {
+	case indexType:
+		return fmt.Sprintf("[%d]", s.idx)
+	case structType:
+		return "." + s.field.Name
+	case mapKeyType:
+		return fmt.Sprintf(".$key(%v)", s.elem)
+	case mapValType:
+		return fmt.Sprintf("[%v]", s.elem)
+	case closureType:
+		return ".$closure"
+	case interfaceType:
+		return fmt.Sprintf(".(%T)", s.val.Interface())
+	case pointerType:
+		return ""
+	case reflectType:
+		return ".$reflect"
+	default:
+		panic("unreachable")
+	}
+}
+
 // DefaultVisitor is a Visitor that visits all values in a
 // reflect.Value graph.
 type DefaultVisitor struct{}

diff --git a/types/reflect.go b/types/reflect.go
@@ -46,7 +46,7 @@ func (s *Serializer) Visit(ctx reflectext.VisitorContext, v reflect.Value) bool
 	case reflectext.ReflectValueType:
 		rv := v.Interface().(reflect.Value)
 		s.appendReflectType(rv.Type())
-		ctx.Visit(rv)
+		ctx.WithReflectValue(v).Visit(rv)
 		return false
 	}
 
@@ -85,7 +85,7 @@ func (d *Deserializer) Visit(ctx reflectext.VisitorContext, v reflect.Value) boo
 			rt = reflect.ArrayOf(length, rt)
 		}
 		rv := reflect.New(rt).Elem()
-		ctx.Visit(rv)
+		ctx.WithReflectValue(v).Visit(rv)
 		v.Set(reflect.ValueOf(rv))
 		return false
 	}
@@ -297,8 +297,10 @@ func (s *Serializer) VisitMap(ctx reflectext.VisitorContext, v reflect.Value) bo
 
 	iter := v.MapRange()
 	for iter.Next() {
-		mapVisitor.Visit(iter.Key())
-		mapVisitor.Visit(iter.Value())
+		key := iter.Key()
+		val := iter.Value()
+		mapVisitor.WithMapKey(v, key).Visit(key)
+		mapVisitor.WithMapValue(v, val).Visit(val)
 	}
 
 	region.Data = regionSerializer.buffer
@@ -342,15 +344,16 @@ func (d *Deserializer) VisitMap(ctx reflectext.VisitorContext, v reflect.Value)
 
 	mapVisitor := ctx.Fork(regionDeserializer)
 
-	nv := reflect.MakeMapWithSize(t, n)
-	v.Set(nv)
+	v.Set(reflect.MakeMapWithSize(t, n))
 	d.store(sID(id), v.Addr().UnsafePointer())
 	for i := 0; i < n; i++ {
-		kv := reflect.New(keyType).Elem()
-		mapVisitor.Visit(kv)
-		vv := reflect.New(valType).Elem()
-		mapVisitor.Visit(vv)
-		v.SetMapIndex(kv, vv)
+		key := reflect.New(keyType).Elem()
+		mapVisitor.WithMapKey(v, key).Visit(key)
+
+		val := reflect.New(valType).Elem()
+		mapVisitor.WithMapKey(v, val).Visit(val)
+
+		v.SetMapIndex(key, val)
 	}
 	return false
 }
@@ -511,9 +514,9 @@ func (s *Serializer) serializeRegion(ctx reflectext.VisitorContext, et reflect.T
 	regionSerializer := s.fork()
 	regionVisitor := ctx.Fork(regionSerializer)
 	if r.len >= 0 { // array
-		data := reflectext.MakeSlice(reflect.SliceOf(r.typ), r.addr, r.len, r.len)
-		for i := 0; i < data.Len(); i++ {
-			regionVisitor.Visit(data.Index(i))
+		v := reflectext.MakeSlice(reflect.SliceOf(r.typ), r.addr, r.len, r.len)
+		for i := 0; i < v.Len(); i++ {
+			regionVisitor.WithArrayIndex(v, i).Visit(v.Index(i))
 		}
 	} else {
 		v := reflect.NewAt(r.typ, r.addr).Elem()
@@ -566,9 +569,9 @@ func (d *Deserializer) deserializeRegion(ctx reflectext.VisitorContext, t reflec
 			} else {
 				regionDeserializer := d.fork(region.Data)
 				regionVisitor := ctx.Fork(regionDeserializer)
-				data := reflectext.MakeSlice(reflect.SliceOf(regionType), p, length, length)
+				v := reflectext.MakeSlice(reflect.SliceOf(regionType), p, length, length)
 				for i := 0; i < length; i++ {
-					regionVisitor.Visit(data.Index(i))
+					regionVisitor.WithArrayIndex(v, i).Visit(v.Index(i))
 				}
 			}
 		} else {