chore: add a custom flag to enable doc extract

Author: alexeagle

BUILD

@@ -1,4 +1,5 @@
 load("@rules_license//rules:license.bzl", "license")
+load("//rules:common_settings.bzl", "bool_flag")
 load("//:bzl_library.bzl", "bzl_library")
 
 package(
@@ -95,3 +96,17 @@ filegroup(
         "//toolchains/unittest:distribution",
     ] + glob(["*.bzl"]),
 )
+
+
+bool_flag(
+    name = "extract_docs",
+    build_setting_default = False,
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "extract_docs_flag",
+    flag_values = {
+        ":extract_docs": "true",
+    },
+)

bzl_library.bzl

@@ -47,8 +47,11 @@ def bzl_library(name, srcs = [], deps = [], **kwargs):
         target_compatible_with = [],
         **kwargs
     )
-    
-    if hasattr(native, "starlark_doc_extract"):
+    enable_doc_extract = select({
+        Label("//:extract_docs_flag"): hasattr(native, "starlark_doc_extract"),
+        "//conditions:default": False,
+    })
+    if enable_doc_extract:
         for i, src in enumerate(srcs):
             native.starlark_doc_extract(
                 name = "{}.doc_extract{}".format(name, i if i > 0 else ""),