1 files changed, 100 insertions, 0 deletions
diff --git a/rules/common_settings.bzl b/rules/common_settings.bzl
new file mode 100644
index 0000000..e80ab09
--- /dev/null
+++ b/rules/common_settings.bzl
@@ -0,0 +1,100 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Common build setting rules
+
+These rules return a BuildSettingInfo with the value of the build setting.
+For label-typed settings, use the native label_flag and label_setting rules.
+
+More documentation on how to use build settings at
+https://docs.bazel.build/versions/master/skylark/config.html#user-defined-build-settings
+"""
+
+BuildSettingInfo = provider(
+    doc = "A singleton provider that contains the raw value of a build setting",
+    fields = {
+        "value": "The value of the build setting in the current configuration. " +
+                 "This value may come from the command line or an upstream transition, " +
+                 "or else it will be the build setting's default.",
+    },
+)
+
+def _impl(ctx):
+    return BuildSettingInfo(value = ctx.build_setting_value)
+
+int_flag = rule(
+    implementation = _impl,
+    build_setting = config.int(flag = True),
+    doc = "An int-typed build setting that can be set on the command line",
+)
+
+int_setting = rule(
+    implementation = _impl,
+    build_setting = config.int(),
+    doc = "An int-typed build setting that cannot be set on the command line",
+)
+
+bool_flag = rule(
+    implementation = _impl,
+    build_setting = config.bool(flag = True),
+    doc = "A bool-typed build setting that can be set on the command line",
+)
+
+bool_setting = rule(
+    implementation = _impl,
+    build_setting = config.bool(),
+    doc = "A bool-typed build setting that cannot be set on the command line",
+)
+
+string_list_flag = rule(
+    implementation = _impl,
+    build_setting = config.string_list(flag = True),
+    doc = "A string list-typed build setting that can be set on the command line",
+)
+
+string_list_setting = rule(
+    implementation = _impl,
+    build_setting = config.string_list(),
+    doc = "A string list-typed build setting that cannot be set on the command line",
+)
+
+def _string_impl(ctx):
+    allowed_values = ctx.attr.values
+    value = ctx.build_setting_value
+    if len(allowed_values) == 0 or value in ctx.attr.values:
+        return BuildSettingInfo(value = value)
+    else:
+        fail("Error setting " + str(ctx.label) + ": invalid value '" + value + "'. Allowed values are " + str(allowed_values))
+
+string_flag = rule(
+    implementation = _string_impl,
+    build_setting = config.string(flag = True),
+    attrs = {
+        "values": attr.string_list(
+            doc = "The list of allowed values for this setting. An error is raised if any other value is given.",
+        ),
+    },
+    doc = "A string-typed build setting that can be set on the command line",
+)
+
+string_setting = rule(
+    implementation = _string_impl,
+    build_setting = config.string(),
+    attrs = {
+        "values": attr.string_list(
+            doc = "The list of allowed values for this setting. An error is raised if any other value is given.",
+        ),
+    },
+    doc = "A string-typed build setting that cannot be set on the command line",
+)