Add support for x_warning_level

Author: Bencodes

src/main/starlark/core/options/opts.kotlinc.bzl

@@ -16,6 +16,23 @@ load("@com_github_jetbrains_kotlin//:capabilities.bzl", _KOTLIN_OPTS = "KOTLIN_O
 load("//src/main/starlark/core/options:convert.bzl", "convert")
 load("//src/main/starlark/core/options:derive.bzl", "derive")
 
+_ALLOWED_SUPPRESS_LEVELS = [
+    "error",
+    "warning",
+    "disabled",
+]
+
+def _map_warning_level(values):
+    if not values:
+        return None
+
+    args = []
+    for k, v in values.items():
+        if v not in _ALLOWED_SUPPRESS_LEVELS:
+            fail("Error: Suppress key '{}' has an invalid value of '{}'".format(k, v))
+        args.append("-Xwarning-level={}:{}".format(k, v))
+    return args
+
 def _map_optin_class_to_flag(values):
     return ["-opt-in=%s" % v for v in values]
 
@@ -425,6 +442,15 @@ default: 'first-only-warn' in language version 2.2+, 'first-only' in version 2.1
             derive.info: derive.repeated_values_for("-Xsuppress-warning="),
         },
     ),
+    "x_warning_level": struct(
+        args = dict(
+            default = {},
+            doc = "Define APIs to opt-in to.",
+        ),
+        type = attr.string_dict,
+        value_to_flag = None,
+        map_value_to_flag = _map_warning_level,
+    ),
     "x_type_enhancement_improvements_strict_mode": struct(
         args = dict(
             default = False,