Ability to concatenate strings

The operand is "++". Example:

```
"foo" ++ "_" ++ "bar"
```

The result will be "foo_bar"

generic_k8s_webhook/config_parser/entrypoint.py

@@ -105,6 +105,7 @@ def _parse_v1beta1(self, raw_list_webhook_config: dict) -> list[Webhook]:
                         op_parser.AnyParser,
                         op_parser.EqualParser,
                         op_parser.SumParser,
+                        op_parser.StrConcatParser,
                         op_parser.NotParser,
                         op_parser.ListParser,
                         op_parser.ForEachParser,

generic_k8s_webhook/config_parser/expr_parser.py

@@ -37,6 +37,7 @@
     ?sum: product
         | sum "+" product   -> add
         | sum "-" product   -> sub
+        | sum "++" product  -> strconcat
 
     ?product: atom
         | product "*" atom  -> mul
@@ -97,6 +98,9 @@ def add(self, items):
     def sub(self, items):
         return op.Sub(op.List(items))
 
+    def strconcat(self, items):
+        return op.StrConcat(op.List(items))
+
     def mul(self, items):
         return op.Mul(op.List(items))
 

generic_k8s_webhook/config_parser/operator_parser.py

@@ -167,6 +167,16 @@ def get_operator_cls(cls) -> operators.BinaryOp:
         return operators.Sum
 
 
+class StrConcatParser(BinaryOpParser):
+    @classmethod
+    def get_name(cls) -> str:
+        return "strconcat"
+
+    @classmethod
+    def get_operator_cls(cls) -> operators.BinaryOp:
+        return operators.StrConcat
+
+
 class UnaryOpParser(OperatorParser):
     def parse(self, op_inputs: dict | list, path_op: str) -> operators.UnaryOp:
         arg = self.meta_op_parser.parse(op_inputs, path_op)

generic_k8s_webhook/operators.py

@@ -154,6 +154,20 @@ def _op(self, lhs, rhs):
         return lhs / rhs
 
 
+class StrConcat(BinaryOp):
+    def input_type(self) -> type | None:
+        return list[str]
+
+    def return_type(self) -> type | None:
+        return str
+
+    def _zero_args_result(self) -> str:
+        return ""
+
+    def _op(self, lhs, rhs):
+        return lhs + rhs
+
+
 class Comp(BinaryOp):
     def get_value(self, contexts: list) -> Any:
         list_arg_values = self.args.get_value(contexts)

tests/conditions_test.yaml

@@ -116,6 +116,16 @@ test_suites:
               sum:
                 - const: 2
             expected_result: 2
+  - name: STRCONCAT
+    tests:
+      - schemas: [v1beta1]
+        cases:
+          - condition:
+              strconcat:
+                - const: "foo"
+                - const: "_"
+                - const: "bar"
+            expected_result: foo_bar
   - name: GET_VALUE
     tests:
       - schemas: [v1alpha1]
@@ -274,6 +284,12 @@ test_suites:
                   - maxCPU: 1
                   - maxCPU: 2
             expected_result: true
+          - condition: '"prefix" ++ "-" ++ "suffix"'
+            expected_result: prefix-suffix
+          - condition: '"prefix-" ++ .name'
+            context:
+              - name: my-name
+            expected_result: prefix-my-name
   - name: LIST_FILTER_MAP_EXPR
     tests:
       - schemas: [v1beta1]