fn: add objects.fields

cmd/chai/doc/functions.go

@@ -3,9 +3,10 @@ package doc
 type functionDocs map[string]string
 
 var packageDocs = map[string]functionDocs{
-	"strings": stringsDocs,
-	"math":    mathDocs,
 	"":        builtinDocs,
+	"math":    mathDocs,
+	"strings": stringsDocs,
+	"objects": objectsDocs,
 }
 
 var builtinDocs = functionDocs{
@@ -39,3 +40,7 @@ var stringsDocs = functionDocs{
 	"ltrim": "The ltrim function returns arg1 with leading characters removed. space by default or arg2",
 	"rtrim": "The rtrim function returns arg1 with trailing characters removed. space by default or arg2",
 }
+
+var objectsDocs = functionDocs{
+	"fields": "The fields function returns the top-level fields of arg1 if arg1 evals to object, otherwise it returns null. It returns an array of TEXT.",
+}

internal/expr/functions/definition.go

@@ -29,6 +29,7 @@ func DefaultPackages() Packages {
 		"":        BuiltinDefinitions(),
 		"math":    MathFunctions(),
 		"strings": StringsDefinitions(),
+		"objects": ObjectsDefinitions(),
 	}
 }
 

internal/expr/functions/object.go

@@ -0,0 +1,73 @@
+package functions
+
+import (
+	"fmt"
+
+	"github.com/chaisql/chai/internal/environment"
+	"github.com/chaisql/chai/internal/expr"
+	"github.com/chaisql/chai/internal/object"
+	"github.com/chaisql/chai/internal/types"
+)
+
+var objectsFunctions = Definitions{
+	"fields": &definition{
+		name:  "fields",
+		arity: 1,
+		constructorFn: func(args ...expr.Expr) (expr.Function, error) {
+			return &ObjectFields{Expr: args[0]}, nil
+		},
+	},
+}
+
+func ObjectsDefinitions() Definitions {
+	return objectsFunctions
+}
+
+// ObjectFields implements the objects.fields function
+// which returns the list of top-level fields of an object.
+// If the argument is not an object, it returns null.
+type ObjectFields struct {
+	Expr expr.Expr
+}
+
+func (s *ObjectFields) Eval(env *environment.Environment) (types.Value, error) {
+	val, err := s.Expr.Eval(env)
+	if err != nil {
+		return nil, err
+	}
+
+	if val.Type() != types.ObjectValue {
+		return types.NewNullValue(), nil
+	}
+
+	obj := types.As[types.Object](val)
+	var fields []string
+	err = obj.Iterate(func(k string, _ types.Value) error {
+		fields = append(fields, k)
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return types.NewArrayValue(object.NewArrayFromSlice(fields)), nil
+}
+
+func (s *ObjectFields) IsEqual(other expr.Expr) bool {
+	if other == nil {
+		return false
+	}
+
+	o, ok := other.(*ObjectFields)
+	if !ok {
+		return false
+	}
+
+	return expr.Equal(s.Expr, o.Expr)
+}
+
+func (s *ObjectFields) Params() []expr.Expr { return []expr.Expr{s.Expr} }
+
+func (s *ObjectFields) String() string {
+	return fmt.Sprintf("objects.fields(%v)", s.Expr)
+}

internal/sqltests/SELECT/objects/fields.sql

@@ -0,0 +1,78 @@
+-- setup:
+CREATE TABLE test(
+    a TEXT,
+    b INT,
+    c BOOL,
+    d DOUBLE,
+    e ARRAY,
+    f OBJECT
+);
+
+INSERT INTO test (a, b, c, d, e, f) VALUES (
+    "FOO",
+    42,
+    true,
+    42.42,
+    ["A", "b", "C", "d", "E"],
+    {
+        a: "HELLO",
+        b: "WorlD"
+    }
+);
+
+-- test: TEXT value
+SELECT objects.fields(a) FROM test;
+/* result:
+{
+    "objects.fields(a)": NULL
+}
+*/
+
+-- test: INT value
+SELECT objects.fields(b) FROM test;
+/* result:
+{
+    "objects.fields(b)": NULL
+}
+*/
+
+
+-- test: BOOL value
+SELECT objects.fields(c) FROM test;
+/* result:
+{
+    "objects.fields(c)": NULL
+}
+*/
+
+-- test: DOUBLE value
+SELECT objects.fields(d) FROM test;
+/* result:
+{
+    "objects.fields(d)": NULL
+}
+*/
+
+-- test: ARRAY value
+SELECT objects.fields(e) FROM test;
+/* result:
+{
+    "objects.fields(e)": NULL
+}
+*/
+
+-- test: OBJECT value
+SELECT objects.fields(f) FROM test;
+/* result:
+{
+    "objects.fields(f)": ["a", "b"]
+}
+*/
+
+-- test: wildcard
+SELECT objects.fields(*) FROM test;
+/* result:
+{
+    "objects.fields(*)": ["a", "b", "c", "d", "e", "f"]
+}
+*/

internal/sqltests/expr/objects.sql

@@ -0,0 +1,35 @@
+-- test: objects.fields
+> objects.fields({})
+[]
+
+> objects.fields({a: 1})
+['a']
+
+> objects.fields({a: 1, b: {c: 2}})
+['a', 'b']
+
+
+> objects.fields(NULL)
+NULL
+
+> objects.fields(true)
+NULL
+
+> objects.fields(false)
+NULL
+
+> objects.fields(1)
+NULL
+
+> objects.fields(1.0)
+NULL
+
+> objects.fields('hello')
+NULL
+
+> objects.fields('\xAA')
+NULL
+
+> objects.fields([])
+NULL
+