private static class ActivationWalker extends MavenTransformer {

        private final Deque<ActivationFrame> stk;

        ActivationWalker(Deque<ActivationFrame> stk, UnaryOperator<String> transformer) {
            super(transformer);
            this.stk = stk;
        }

        private ActivationFrame nextFrame(String property) {
            return new ActivationFrame(property, Optional.empty());
        }

 * limitations under the License.
 */

package org.gradle.api.internal.provider

import com.google.common.collect.ImmutableCollection
import org.gradle.api.Task
import org.gradle.api.Transformer
import org.gradle.api.provider.Property
import org.gradle.api.provider.Provider
import org.gradle.internal.Describables
import org.gradle.util.internal.TextUtil
import org.spockframework.lang.Wildcard

 * limitations under the License.
 */

package org.gradle.api.internal.provider

import com.google.common.collect.ImmutableMap
import org.gradle.api.Task
import org.gradle.api.Transformer
import org.gradle.api.provider.MapProperty
import org.gradle.api.provider.Property
import org.gradle.api.provider.Provider
import org.gradle.internal.Describables
import org.gradle.internal.state.ManagedFactory

			return obj, nil
		}), nil); err != nil {
		t.Fatalf("GuaranteedUpdate failed: %v", err)
	}

	// Now trigger watch error by injecting failing transformer.
	revertTransformer := store.UpdatePrefixTransformer(
		func(previousTransformer *PrefixTransformer) value.Transformer {
			return &failingTransformer{}
		})
	defer revertTransformer()

* one takes a `{javaApi}/java/io/FilterReader.html[FilterReader]` and is designed to work with Ant filters, such as `ReplaceTokens`
* one takes a closure or link:{javadocPath}/org/gradle/api/Transformer.html[Transformer] that defines the transformation for each line of the source file

Note that both variants assume the source files are text-based.

          // setFuture, so a user couldn't break the chain by doing this themselves.  It is also
          // potentially common if someone writes a recursive Futures.transformAsync transformer.
          future = setFuture.owner;
          if (future.value == setFuture) {
            Object valueToSet = getFutureValue(setFuture.future);
            if (ATOMIC_HELPER.casValue(future, setFuture, valueToSet)) {

          // setFuture, so a user couldn't break the chain by doing this themselves.  It is also
          // potentially common if someone writes a recursive Futures.transformAsync transformer.
          future = setFuture.owner;
          if (future.value == setFuture) {
            Object valueToSet = getFutureValue(setFuture.future);
            if (ATOMIC_HELPER.casValue(future, setFuture, valueToSet)) {