Allow starlark rules to be build settings.
For skylark rules that are declared build settings, we auto-add a nonconfigurable build_setting_default attribute which must be set on a per target basis. We also add access to the build setting value via the rule context object. All of this functionality is hidden behind the --experimental_build_setting_api flag which by default is flipped off.
This includes:
- Add a build_setting parameter to starlark rule construction.
- If a starlark rule sets the build_setting parameter, auto-add a mandatory 'build_setting_default' attribute of the same type.
- Allow the value of a build setting skylark rules to be accessed via ctx.build_setting_value.
- Get rid of BuildSettingDescriptor since we don't need both it and BuildSetting.
- Add the --experimental_build_setting_api flag to SkylarkSemantics flags.
Work towards issue #5577
PiperOrigin-RevId: 219537101
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkRuleContextApi.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkRuleContextApi.java
index 979a447..20e04fa 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkRuleContextApi.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkRuleContextApi.java
@@ -34,6 +34,7 @@
import com.google.devtools.build.lib.syntax.SkylarkList;
import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
+import com.google.devtools.build.lib.syntax.SkylarkSemantics.FlagIdentifier;
import java.util.Map;
import javax.annotation.Nullable;
@@ -229,6 +230,17 @@
public BuildConfigurationApi getHostConfiguration() throws EvalException;
@SkylarkCallable(
+ name = "build_setting_value",
+ structField = true,
+ enableOnlyWithFlag = FlagIdentifier.EXPERIMENTAL_BUILD_SETTING_API,
+ doc =
+ "<b>Experimental. This field is experimental and subject to change at any time. Do not "
+ + "depend on it.</b> <p>Returns the value of the build setting that is represented "
+ + "by the current target. It is an error to access this field for rules that do not "
+ + "set the <code>build_setting</code> attribute in their rule definition.")
+ public Object getBuildSettingValue() throws EvalException;
+
+ @SkylarkCallable(
name = "coverage_instrumented",
doc =
"Returns whether code coverage instrumentation should be generated when performing "
