topdown: Add urlquery.decode_object builtin

This builtin is the reverse of the encode_object builtin and
makes it easier to use the URI query parameters in policies

Fixes open-policy-agent#2647

Signed-off-by: Frederic <frederic.vanreet@icloud.com>

ast/builtins.go

@@ -135,6 +135,7 @@ var DefaultBuiltins = [...]*Builtin{
 	URLQueryDecode,
 	URLQueryEncode,
 	URLQueryEncodeObject,
+	URLQueryDecodeObject,
 	YAMLMarshal,
 	YAMLUnmarshal,
 
@@ -1283,6 +1284,17 @@ var URLQueryEncodeObject = &Builtin{
 	),
 }
 
+// URLQueryDecodeObject decodes the given URL query string into an object.
+var URLQueryDecodeObject = &Builtin{
+	Name: "urlquery.decode_object",
+	Decl: types.NewFunction(
+		types.Args(types.S),
+		types.NewObject(nil, types.NewDynamicProperty(
+			types.S,
+			types.NewArray(nil, types.S))),
+	),
+}
+
 // YAMLMarshal serializes the input term.
 var YAMLMarshal = &Builtin{
 	Name: "yaml.marshal",

capabilities.json

@@ -3043,6 +3043,31 @@
         "type": "function"
       }
     },
+    {
+      "name": "urlquery.decode_object",
+      "decl": {
+        "args": [
+          {
+            "type": "string"
+          }
+        ],
+        "result": {
+          "dynamic": {
+            "key": {
+              "type": "string"
+            },
+            "value": {
+              "dynamic": {
+                "type": "string"
+              },
+              "type": "array"
+            }
+          },
+          "type": "object"
+        },
+        "type": "function"
+      }
+    },
     {
       "name": "urlquery.encode",
       "decl": {

docs/content/policy-reference.md

@@ -447,6 +447,7 @@ The following table shows examples of how ``glob.match`` works:
 | <span class="opa-keep-it-together">``output := urlquery.encode(string)``</span> | ``output`` is ``string`` serialized to a URL query parameter encoded string |
 | <span class="opa-keep-it-together">``output := urlquery.encode_object(object)``</span> | ``output`` is ``object`` serialized to a URL query parameter encoded string |
 | <span class="opa-keep-it-together">``output := urlquery.decode(string)``</span> | ``output`` is ``string`` deserialized from a URL query parameter encoded string |
+| <span class="opa-keep-it-together">``output := urlquery.decode_object(string)``</span> | ``output`` is ``object`` deserialized from a URL query parameter string |
 | <span class="opa-keep-it-together">``output := json.marshal(x)``</span> | ``output`` is ``x`` serialized to a JSON string |
 | <span class="opa-keep-it-together">``output := json.unmarshal(string)``</span> | ``output`` is ``string`` deserialized to a term from a JSON encoded string |
 | <span class="opa-keep-it-together">``output := yaml.marshal(x)``</span> | ``output`` is ``x`` serialized to a YAML string |

test/cases/testdata/urlbuiltins/test-urlbuiltins-1076.yaml

@@ -0,0 +1,34 @@
+cases:
+- modules:
+  - |
+    package decode_object
+
+    p = x {
+      x = urlquery.decode_object("a=value_a1&b=value_b&a=value_a2")
+    }
+  note: urlbuiltins/decode_object multiple
+  query: data.decode_object.p = x
+  want_result:
+  - x: {"a": ["value_a1", "value_a2"], "b": ["value_b"]}
+- modules:
+  - |
+    package decode_object
+
+    p = x {
+      x = urlquery.decode_object("a=value_a1&b")
+    }
+  note: urlbuiltins/decode_object empty parameter
+  query: data.decode_object.p = x
+  want_result:
+  - x: {"a": ["value_a1"], "b": [""]}
+- modules:
+  - |
+    package decode_object
+
+    p = x {
+      x = urlquery.decode_object("")
+    }
+  note: urlbuiltins/decode_object empty string
+  query: data.decode_object.p = x
+  want_result:
+  - x: {}

topdown/encoding.go

@@ -158,6 +158,29 @@ func builtinURLQueryEncodeObject(a ast.Value) (ast.Value, error) {
 	return ast.String(query.Encode()), nil
 }
 
+func builtinURLQueryDecodeObject(bctx BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
+	query, err := builtins.StringOperand(operands[0].Value, 1)
+	if err != nil {
+		return err
+	}
+
+	queryParams, err := url.ParseQuery(string(query))
+	if err != nil {
+		return err
+	}
+
+	queryObject := ast.NewObject()
+	for k, v := range queryParams {
+		paramsArray := make([]*ast.Term, len(v))
+		for i, param := range v {
+			paramsArray[i] = ast.StringTerm(param)
+		}
+		queryObject.Insert(ast.StringTerm(k), ast.ArrayTerm(paramsArray...))
+	}
+
+	return iter(ast.NewTerm(queryObject))
+}
+
 func builtinYAMLMarshal(a ast.Value) (ast.Value, error) {
 
 	asJSON, err := ast.JSON(a)
@@ -212,6 +235,7 @@ func init() {
 	RegisterFunctionalBuiltin1(ast.URLQueryDecode.Name, builtinURLQueryDecode)
 	RegisterFunctionalBuiltin1(ast.URLQueryEncode.Name, builtinURLQueryEncode)
 	RegisterFunctionalBuiltin1(ast.URLQueryEncodeObject.Name, builtinURLQueryEncodeObject)
+	RegisterBuiltinFunc(ast.URLQueryDecodeObject.Name, builtinURLQueryDecodeObject)
 	RegisterFunctionalBuiltin1(ast.YAMLMarshal.Name, builtinYAMLMarshal)
 	RegisterFunctionalBuiltin1(ast.YAMLUnmarshal.Name, builtinYAMLUnmarshal)
 }