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Add list flatten() #980

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Merged
merged 4 commits into from
Aug 16, 2024
Merged

Add list flatten() #980

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3c794d9
Add list flatten()
fabriziosestito Jul 10, 2024
c9055e2
Flatten defaults to single level, add flattenDeep
fabriziosestito Jul 15, 2024
f12810c
Change signatures from list(T) to list(dyn)
fabriziosestito Jul 18, 2024
717d839
Refactor in flatten with optional level; add versioning
fabriziosestito Aug 12, 2024
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103 changes: 98 additions & 5 deletions ext/lists.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ package ext

import (
"fmt"
"math"

"github.com/google/cel-go/cel"
"github.com/google/cel-go/common/types"
Expand All @@ -35,21 +36,67 @@ import (
//
// [1,2,3,4].slice(1, 3) // return [2, 3]
// [1,2,3,4].slice(2, 4) // return [3 ,4]
func Lists() cel.EnvOption {
return cel.Lib(listsLib{})
//
// # Flatten
//
// Flattens a list recursively.
// If an optional depth is provided, the list is flattened to a the specificied level.
// A negative depth value flattens the list recursively to its deepest level.
//
// <list>.flatten(<list>) -> <list>
// <list>.flatten(<list>, <int>) -> <list>
//
// Examples:
//
// [1,[2,3],[4]].flatten() // return [1, 2, 3, 4]
// [1,[2,[3,4]]].flatten() // return [1, 2, [3, 4]]
// [1,2,[],[],[3,4]].flatten() // return [1, 2, 3, 4]
// [1,[2,[3,[4]]]].flatten(2) // return [1, 2, 3, [4]]
// [1,[2,[3,[4]]]].flatten(-1) // return [1, 2, 3, 4]
func Lists(options ...ListsOption) cel.EnvOption {
l := &listsLib{
version: math.MaxUint32,
}
for _, o := range options {
l = o(l)
}

return cel.Lib(l)
}

type listsLib struct{}
type listsLib struct {
version uint32
}

// LibraryName implements the SingletonLibrary interface method.
func (listsLib) LibraryName() string {
return "cel.lib.ext.lists"
}

// ListsOption is a functional interface for configuring the strings library.
type ListsOption func(*listsLib) *listsLib

// ListsVersion configures the version of the string library.
//
// The version limits which functions are available. Only functions introduced
// below or equal to the given version included in the library. If this option
// is not set, all functions are available.
//
// See the library documentation to determine which version a function was introduced.
// If the documentation does not state which version a function was introduced, it can
// be assumed to be introduced at version 0, when the library was first created.
func ListsVersion(version uint32) ListsOption {
return func(lib *listsLib) *listsLib {
lib.version = version
return lib
}
}

// CompileOptions implements the Library interface method.
func (listsLib) CompileOptions() []cel.EnvOption {
func (lib listsLib) CompileOptions() []cel.EnvOption {
listType := cel.ListType(cel.TypeParamType("T"))
return []cel.EnvOption{
listDyn := cel.ListType(cel.DynType)
opts := []cel.EnvOption{
cel.Function("slice",
cel.MemberOverload("list_slice",
[]*cel.Type{listType, cel.IntType, cel.IntType}, listType,
Expand All @@ -66,6 +113,33 @@ func (listsLib) CompileOptions() []cel.EnvOption {
),
),
}
if lib.version >= 1 {
opts = append(opts,
cel.Function("flatten",
cel.MemberOverload("list_flatten",
[]*cel.Type{listDyn}, listDyn,
cel.UnaryBinding(func(arg ref.Val) ref.Val {
list := arg.(traits.Lister)
flatList := flatten(list, 1)
return types.DefaultTypeAdapter.NativeToValue(flatList)
}),
),
),
cel.Function("flatten",
cel.MemberOverload("list_flatten_int",
[]*cel.Type{listDyn, types.IntType}, listDyn,
cel.BinaryBinding(func(arg1, arg2 ref.Val) ref.Val {
list := arg1.(traits.Lister)
depth := arg2.(types.Int)
flatList := flatten(list, int64(depth))
return types.DefaultTypeAdapter.NativeToValue(flatList)
}),
),
),
)
}

return opts
}

// ProgramOptions implements the Library interface method.
Expand All @@ -92,3 +166,22 @@ func slice(list traits.Lister, start, end types.Int) (ref.Val, error) {
}
return types.DefaultTypeAdapter.NativeToValue(newList), nil
}

func flatten(list traits.Lister, depth int64) []ref.Val {
var newList []ref.Val
iter := list.Iterator()

for iter.HasNext() == types.True {
val := iter.Next()
nestedList, isList := val.(traits.Lister)

if !isList || depth == 0 {
newList = append(newList, val)
continue
} else {
newList = append(newList, flatten(nestedList, depth-1)...)
}
}

return newList
}
6 changes: 6 additions & 0 deletions ext/lists_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,12 @@ func TestLists(t *testing.T) {
{expr: `[1,2,3,4].slice(0, 10)`, err: "cannot slice(0, 10), list is length 4"},
{expr: `[1,2,3,4].slice(-5, 10)`, err: "cannot slice(-5, 10), negative indexes not supported"},
{expr: `[1,2,3,4].slice(-5, -3)`, err: "cannot slice(-5, -3), negative indexes not supported"},
{expr: `[].flatten() == []`},
{expr: `[1,2,3,4].flatten() == [1,2,3,4]`},
{expr: `[1,[2,[3,4]]].flatten() == [1,2,[3,4]]`},
{expr: `[1,2,[],[],[3,4]].flatten() == [1,2,3,4]`},
{expr: `[1,[2,[3,4]]].flatten(2) == [1,2,3,4]`},
{expr: `[1,[2,[3,[4]]]].flatten(-1) == [1,2,3,4]`},
}

env := testListsEnv(t)
Expand Down