feat(stdlib): switch testing.diff to use experimental.diff as its base (

#5000)

This causes the `_diff` function to use the diff implementation in
`experimental` as the base diff implementation when the feature flag is
set.

This will cause diff to use a longest common subsequence algorithm to
compute the diff.

This is behind a feature flag in case it has some unknown complication.

execute/executetest/dependencies.go

@@ -37,6 +37,7 @@ var testFlags = map[string]interface{}{
 	"narrowTransformationLimit": true,
 	"optimizeStateTracking":     true,
 	"optimizeSetTransformation": true,
+	"experimentalTestingDiff":   true,
 }
 
 type TestFlagger map[string]interface{}

internal/feature/flags.yml

@@ -93,3 +93,9 @@
   key: vectorizedConst
   default: false
   contact: Owen Nelson
+
+- name: Experimental Testing Diff
+  description: Switches testing.diff to use experimental.diff
+  key: experimentalTestingDiff
+  default: false
+  contact: Jonathan Sternberg

stdlib/experimental/diff.go

@@ -93,7 +93,7 @@ func createDiffTransformation(id execute.DatasetID, mode execute.AccumulationMod
 	}
 
 	wantID, gotID := a.Parents()[0], a.Parents()[1]
-	return newDiffTransformation(id, pspec, wantID, gotID, a.Allocator())
+	return NewDiffTransformation(id, pspec, wantID, gotID, a.Allocator())
 }
 
 type diffTransformation struct {
@@ -107,7 +107,7 @@ type diffTransformation struct {
 	wantID, gotID execute.DatasetID
 }
 
-func newDiffTransformation(id execute.DatasetID, spec *DiffProcedureSpec, wantID, gotID execute.DatasetID, mem memory.Allocator) (execute.Transformation, execute.Dataset, error) {
+func NewDiffTransformation(id execute.DatasetID, spec *DiffProcedureSpec, wantID, gotID execute.DatasetID, mem memory.Allocator) (execute.Transformation, execute.Dataset, error) {
 	tr := &diffTransformation{
 		d:   execute.NewTransportDataset(id, mem),
 		mem: mem,

stdlib/testing/diff.go

@@ -11,9 +11,11 @@ import (
 	"github.com/influxdata/flux/codes"
 	"github.com/influxdata/flux/execute"
 	"github.com/influxdata/flux/internal/errors"
+	"github.com/influxdata/flux/internal/feature"
 	"github.com/influxdata/flux/memory"
 	"github.com/influxdata/flux/plan"
 	"github.com/influxdata/flux/runtime"
+	"github.com/influxdata/flux/stdlib/experimental"
 )
 
 const DiffKind = "diff"
@@ -296,14 +298,20 @@ func createDiffTransformation(id execute.DatasetID, mode execute.AccumulationMod
 		return nil, nil, errors.New(codes.Internal, "diff should have exactly 2 parents")
 	}
 
+	wantID, gotID := a.Parents()[0], a.Parents()[1]
+	if feature.ExperimentalTestingDiff().Enabled(a.Context()) {
+		spec := &experimental.DiffProcedureSpec{}
+		return experimental.NewDiffTransformation(id, spec, wantID, gotID, a.Allocator())
+	}
+
 	cache := execute.NewTableBuilderCache(a.Allocator())
 	dataset := execute.NewDataset(id, mode, cache)
 	pspec, ok := spec.(*DiffProcedureSpec)
 	if !ok {
 		return nil, nil, errors.Newf(codes.Internal, "invalid spec type %T", pspec)
 	}
 
-	transform := NewDiffTransformation(dataset, cache, pspec, a.Parents()[0], a.Parents()[1], a.Allocator())
+	transform := NewDiffTransformation(dataset, cache, pspec, wantID, gotID, a.Allocator())
 
 	return transform, dataset, nil
 }