feat: add list amender tests + other fixes/cleanup

datamodel/amender.go

@@ -20,17 +20,17 @@ type containerAmender interface {
 	Empty() bool
 	Length() int64
 	Clear()
-	Values() (Node, error) // returns a list node with the values
+	Values() (Node, error) // returns a list Node with the values
 
 	NodeAmender
 }
 
 // MapAmender adds a map-like interface to NodeAmender
 type MapAmender interface {
-	Put(key Node, value Node) error
-	Get(key Node) (Node, error)
-	Remove(key Node) (bool, error)
-	Keys() (Node, error) // returns a list node with the keys
+	Put(key string, value Node) error
+	Get(key string) (Node, error)
+	Remove(key string) (bool, error)
+	Keys() (Node, error) // returns a list Node with the keys
 
 	containerAmender
 }
@@ -39,8 +39,17 @@ type MapAmender interface {
 type ListAmender interface {
 	Get(idx int64) (Node, error)
 	Remove(idx int64) error
-	Append(values Node) error            // accepts a list node
-	Insert(idx int64, values Node) error // accepts a list node
+	// Append will add Node(s) to the end of the list. It can accept a list Node with multiple values to append.
+	Append(value Node) error
+	// Insert will add Node(s) at the specified index and shift subsequent elements to the right. It can accept a list
+	// Node with multiple values to insert.
+	// Passing an index equal to the length of the list will add Node(s) to the end of the list like Append.
+	Insert(idx int64, value Node) error
+	// Set will add Node(s) at the specified index and shift subsequent elements to the right. It can accept a list Node
+	// with multiple values to insert.
+	// Passing an index equal to the length of the list will add Node(s) to the end of the list like Append.
+	// Set is different from Insert in that it will start its insertion at the specified index, overwriting it in the
+	// process, while Insert will only add the Node(s).
 	Set(idx int64, value Node) error
 
 	containerAmender

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/multiformats/go-multihash v0.2.3
 	github.com/polydawn/refmt v0.89.0
 	github.com/warpfork/go-testmark v0.12.1
+	golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1
 	gopkg.in/yaml.v2 v2.4.0
 )
 

go.sum

@@ -59,6 +59,8 @@ github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0/go.mod h1:x6AKhvS
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.1.0 h1:MDRAIl0xIo9Io2xV565hzXHw3zVseKrJKodhohM5CjU=
 golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
+golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 h1:MGwJjxBy0HJshjDNfLsYO8xppfqWlA5ZT9OhtUUhTNw=
+golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=

node/basicnode/list.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"reflect"
 
+	"golang.org/x/exp/slices"
+
 	"github.com/ipld/go-ipld-prime/datamodel"
 	"github.com/ipld/go-ipld-prime/node/mixins"
 )
@@ -160,6 +162,10 @@ func (nb *plainList__Builder) Reset() {
 // -- NodeAmender -->
 
 func (nb *plainList__Builder) Transform(path datamodel.Path, transform datamodel.AmendFn) (datamodel.Node, error) {
+	return nb.transform(path, transform, true)
+}
+
+func (nb *plainList__Builder) transform(path datamodel.Path, transform datamodel.AmendFn, replace bool) (datamodel.Node, error) {
 	// Can only transform the root of the node or an immediate child.
 	if path.Len() > 1 {
 		panic("misuse")
@@ -217,20 +223,20 @@ func (nb *plainList__Builder) Transform(path datamodel.Path, transform datamodel
 	if newChildVal, err := transform(prevChildVal); err != nil {
 		return nil, err
 	} else if newChildVal == nil {
-		newX := make([]datamodel.NodeAmender, nb.w.Length()-1)
-		copy(newX, nb.w.x[:childIdx])
-		copy(newX[:childIdx], nb.w.x[childIdx+1:])
-		nb.w.x = newX
-	} else if err = nb.storeChildAmender(childIdx, newChildVal); err != nil {
+		// Ref: https://pkg.go.dev/golang.org/x/exp/slices#Delete
+		idx := int(childIdx)
+		nb.w.x[idx] = nil
+		nb.w.x = slices.Delete(nb.w.x, idx, idx+1)
+	} else if err = nb.storeChildAmender(childIdx, newChildVal, replace); err != nil {
 		return nil, err
 	}
 	return prevChildVal, nil
 }
 
-func (nb *plainList__Builder) storeChildAmender(childIdx int64, a datamodel.NodeAmender) error {
+func (nb *plainList__Builder) storeChildAmender(childIdx int64, a datamodel.NodeAmender, replace bool) error {
 	var elems []datamodel.NodeAmender
 	n := a.Build()
-	if (n.Kind() == datamodel.Kind_List) && (n.Length() > 0) {
+	if n.Kind() == datamodel.Kind_List {
 		elems = make([]datamodel.NodeAmender, n.Length())
 		// The following logic uses a transformed list (if there is one) to perform both insertions (needed by JSON
 		// Patch) and replacements (needed by `focus` and `walk`), while also providing the flexibility to insert more
@@ -258,14 +264,36 @@ func (nb *plainList__Builder) storeChildAmender(childIdx int64, a datamodel.Node
 		elems = []datamodel.NodeAmender{Prototype.Any.AmendingBuilder(n)}
 	}
 	if childIdx == nb.w.Length() {
+		// Operations at the end of the list are straightforward - just append, and we're done.
 		nb.w.x = append(nb.w.x, elems...)
-	} else {
-		numElems := int64(len(elems))
-		newX := make([]datamodel.NodeAmender, nb.w.Length()+numElems-1)
-		copy(newX, nb.w.x[:childIdx])
-		copy(newX[childIdx:], elems)
-		copy(newX[childIdx+numElems:], nb.w.x[childIdx+1:])
-		nb.w.x = newX
+		return nil
+	}
+	numElems := len(elems)
+	if numElems > 0 {
+		if nb.w.x == nil {
+			// Allocate storage space
+			nb.w.x = make([]datamodel.NodeAmender, numElems)
+		} else {
+			// Allocate storage space
+			numElemsToAdd := numElems
+			if replace {
+				// We'll be replacing an existing element and need one slot less than the total number of elements being
+				// added.
+				numElemsToAdd--
+			}
+			nb.w.x = slices.Grow(nb.w.x, numElemsToAdd)
+		}
+		copyStartIdx := 0
+		if replace {
+			// Use the first passed element to replace the element currently at the specified index
+			nb.w.x[childIdx] = elems[0]
+			copyStartIdx++
+		}
+		if !replace || (numElems > 1) {
+			// If more elements were specified, insert them after the specified index.
+			// Ref: https://pkg.go.dev/golang.org/x/exp/slices#Insert
+			nb.w.x = slices.Insert(nb.w.x, int(childIdx)+copyStartIdx, elems[copyStartIdx:]...)
+		}
 	}
 	return nil
 }
@@ -284,31 +312,35 @@ func (nb *plainList__Builder) Remove(idx int64) error {
 	return err
 }
 
-func (nb *plainList__Builder) Append(values datamodel.Node) error {
-	// Passing an index equal to the length of the list will append the passed values to the end of the list
-	return nb.Insert(nb.Length(), values)
+func (nb *plainList__Builder) Append(value datamodel.Node) error {
+	return nb.Set(nb.Length(), value)
+}
+
+func (nb *plainList__Builder) Insert(idx int64, value datamodel.Node) error {
+	return nb.addElements(idx, value, false)
+}
+
+func (nb *plainList__Builder) Set(idx int64, value datamodel.Node) error {
+	return nb.addElements(idx, value, true)
 }
 
-func (nb *plainList__Builder) Insert(idx int64, values datamodel.Node) error {
+func (nb *plainList__Builder) addElements(idx int64, value datamodel.Node, replaced bool) error {
 	var ps datamodel.PathSegment
 	if idx == nb.Length() {
 		ps = datamodel.PathSegmentOfString("-") // indicates appending to the end of the list
 	} else {
 		ps = datamodel.PathSegmentOfInt(idx)
 	}
-	_, err := nb.Transform(
+	_, err := nb.transform(
 		datamodel.NewPath([]datamodel.PathSegment{ps}),
 		func(_ datamodel.Node) (datamodel.NodeAmender, error) {
-			return Prototype.Any.AmendingBuilder(values), nil
+			return Prototype.Any.AmendingBuilder(value), nil
 		},
+		replaced,
 	)
 	return err
 }
 
-func (nb *plainList__Builder) Set(idx int64, value datamodel.Node) error {
-	return nb.Insert(idx, value)
-}
-
 func (nb *plainList__Builder) Empty() bool {
 	return nb.Length() == 0
 }