Migrate SkylarkNativeModule methods to use @SkylarkCallable instead of @SkylarkSignature

Most notably, this involves introduction of a new function abstraction, BuiltinMethod, which can wrap a {objc, SkylarkCallable} pair into a BaseFunction for later calling. (This is required due to the current layer of indirection on the end "native" module)

RELNOTES: None.
PiperOrigin-RevId: 191642467

1 files changed, 15 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
index 7a807f5e20..597508f04d 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
@@ -318,6 +318,21 @@ public final class FuncallExpression extends Expression {
   }
 
   /**
+   * Returns a {@link BuiltinCallable} representing a {@link SkylarkCallable}-annotated instance
+   * method of a given object with the given method name.
+   */
+  public static BuiltinCallable getBuiltinCallable(Object obj, String methodName) {
+    Class<?> objClass = obj.getClass();
+    List<MethodDescriptor> methodDescriptors = getMethods(objClass, methodName);
+    if (methodDescriptors.size() != 1) {
+      throw new IllegalStateException(String.format(
+          "Expected exactly 1 method named '%s' in %s, but found %s",
+          methodName, objClass, methodDescriptors.size()));
+    }
+    return new BuiltinCallable(methodName, obj, methodDescriptors.get(0));
+  }
+
+  /**
    * Invokes the given structField=true method and returns the result.
    *
    * @param methodDescriptor the descriptor of the method to invoke