feat: implement std.isNull

builtins.go

@@ -2533,6 +2533,11 @@ func builtInObjectRemoveKey(i *interpreter, objv value, keyv value) (value, erro
 	), nil
 }
 
+func builtinIsNull(i *interpreter, v value) (value, error) {
+    _, isNull := v.(*valueNull)
+    return makeValueBoolean(isNull), nil
+}
+
 // Utils for builtins - TODO(sbarzowski) move to a separate file in another commit
 
 type builtin interface {
@@ -2890,6 +2895,7 @@ var funcBuiltins = buildBuiltinMap([]builtin{
 	&unaryBuiltin{name: "sum", function: builtinSum, params: ast.Identifiers{"arr"}},
 	&unaryBuiltin{name: "avg", function: builtinAvg, params: ast.Identifiers{"arr"}},
 	&binaryBuiltin{name: "contains", function: builtinContains, params: ast.Identifiers{"arr", "elem"}},
+	&unaryBuiltin{name: "isNull", function: builtinIsNull, params: ast.Identifiers{"x"}},
 
 	// internal
 	&unaryBuiltin{name: "$objectFlatMerge", function: builtinUglyObjectFlatMerge, params: ast.Identifiers{"x"}},

linter/internal/types/stdlib.go

@@ -51,6 +51,7 @@ func prepareStdlib(g *typeGraph) {
 		"isOdd":      g.newSimpleFuncType(boolType, "x"),
 		"isInteger":  g.newSimpleFuncType(boolType, "x"),
 		"isDecimal":  g.newSimpleFuncType(boolType, "x"),
+		"isNull":     g.newSimpleFuncType(boolType, "x"),
 
 		// Mathematical utilities
 		"abs":      g.newSimpleFuncType(numberType, "n"),

testdata/builtinIsNull.golden

@@ -0,0 +1 @@
+true

testdata/builtinIsNull.jsonnet

@@ -0,0 +1 @@
+std.isNull(null)

testdata/builtinIsNull2.golden

@@ -0,0 +1 @@
+false

testdata/builtinIsNull2.jsonnet

@@ -0,0 +1 @@
+std.isNull("foo")