src/test/java/com/google/devtools/build/skyframe/GraphTester.java - bazel - Git at Google

 // Copyright 2014 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.
 package com.google.devtools.build.skyframe;

 import static com.google.common.truth.Truth.assertThat;

 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Interner;
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.concurrent.BlazeInterners;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.ExtendedEventHandler.Postable;
 import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.skyframe.SkyFunction.Environment;
 import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import javax.annotation.Nullable;

 /**
  * A helper class to create graphs and run skyframe tests over these graphs.
  *
  * <p>There are two types of values, computing values, which may not be set to a constant value,
  * and leaf values, which must be set to a constant value and may not have any dependencies.
  *
  * <p>Note that the value builder looks into the test values created here to determine how to
  * behave. However, skyframe will only re-evaluate the value and call the value builder if any of
  * its dependencies has changed. That means in order to change the set of dependencies of a value,
  * you need to also change one of its previous dependencies to force re-evaluation. Changing a
  * computing value does not mark it as modified.
  */
 public class GraphTester {

   public static final SkyFunctionName NODE_TYPE = SkyFunctionName.FOR_TESTING;
   private final Map<SkyFunctionName, SkyFunction> functionMap = new HashMap<>();

   private final Map<SkyKey, TestFunction> values = new HashMap<>();
   private final Set<SkyKey> modifiedValues = new LinkedHashSet<>();

   public GraphTester() {
     functionMap.put(NODE_TYPE, new DelegatingFunction());
     functionMap.put(FOR_TESTING_NONHERMETIC, new DelegatingFunction());
   }

   public TestFunction getOrCreate(String name) {
     return getOrCreate(skyKey(name));
   }

   public TestFunction getOrCreate(SkyKey key) {
     return getOrCreate(key, false);
   }

   public TestFunction getOrCreate(SkyKey key, boolean markAsModified) {
     TestFunction result = values.get(key);
     if (result == null) {
       result = new TestFunction();
       values.put(key, result);
     } else if (markAsModified) {
       modifiedValues.add(key);
     }
     return result;
   }

   public TestFunction set(String key, SkyValue value) {
     return set(skyKey(key), value);
   }

   public TestFunction set(SkyKey key, SkyValue value) {
     return getOrCreate(key, true).setConstantValue(value);
   }

   public ImmutableSet<SkyKey> getModifiedValues() {
     return ImmutableSet.copyOf(modifiedValues);
   }

   public void clearModifiedValues() {
     modifiedValues.clear();
   }

   public SkyFunction getFunction() {
     return new SkyFunction() {
       @Override
       public SkyValue compute(SkyKey key, Environment env)
           throws SkyFunctionException, InterruptedException {
         TestFunction builder = values.get(key);
         Preconditions.checkState(builder != null, "No TestFunction for " + key);
         if (builder.builder != null) {
           return builder.builder.compute(key, env);
         }
         if (builder.warning != null) {
           env.getListener().handle(Event.warn(builder.warning));
         }
         if (builder.progress != null) {
           env.getListener().handle(Event.progress(builder.progress));
         }
         if (builder.postable != null) {
           env.getListener().post(builder.postable);
         }
         Map<SkyKey, SkyValue> deps = new LinkedHashMap<>();
         boolean oneMissing = false;
         for (Pair<SkyKey, SkyValue> dep : builder.deps) {
           SkyValue value;
           if (dep.second == null) {
             value = env.getValue(dep.first);
           } else {
             try {
               value = env.getValueOrThrow(dep.first, SomeErrorException.class);
             } catch (SomeErrorException e) {
               value = dep.second;
             }
           }
           if (value == null) {
             oneMissing = true;
           } else {
             deps.put(dep.first, value);
           }
           Preconditions.checkState(
               oneMissing == env.valuesMissing(), "%s %s %s", dep, value, env.valuesMissing());
         }
         if (env.valuesMissing()) {
           return null;
         }

         if (builder.hasTransientError) {
           throw new GenericFunctionException(new SomeErrorException(key.toString()),
               Transience.TRANSIENT);
         }
         if (builder.hasError) {
           throw new GenericFunctionException(new SomeErrorException(key.toString()),
               Transience.PERSISTENT);
         }

         if (builder.value != null) {
           return builder.value;
         }

         if (Thread.currentThread().isInterrupted()) {
           throw new InterruptedException(key.toString());
         }

         return builder.computer.compute(deps, env);
       }

       @Nullable
       @Override
       public String extractTag(SkyKey skyKey) {
         return values.get(skyKey).tag;
       }
     };
   }

   public static SkyKey skyKey(String key) {
     return Key.create(key);
   }

   public static NonHermeticKey nonHermeticKey(String key) {
     return NonHermeticKey.create(key);
   }

   /** A value in the testing graph that is constructed in the tester. */
   public static class TestFunction {
     // TODO(bazel-team): We could use a multiset here to simulate multi-pass dependency discovery.
     private final Set<Pair<SkyKey, SkyValue>> deps = new LinkedHashSet<>();
     private SkyValue value;
     private ValueComputer computer;
     private SkyFunction builder = null;

     private boolean hasTransientError;
     private boolean hasError;

     private String warning;
     private String progress;
     private Postable postable;

     private String tag;

     public TestFunction addDependency(String name) {
       return addDependency(skyKey(name));
     }

     public TestFunction addDependency(SkyKey key) {
       deps.add(Pair.<SkyKey, SkyValue>of(key, null));
       return this;
     }

     public TestFunction removeDependency(String name) {
       return removeDependency(skyKey(name));
     }

     public TestFunction removeDependency(SkyKey key) {
       deps.remove(Pair.<SkyKey, SkyValue>of(key, null));
       return this;
     }

     public TestFunction addErrorDependency(String name, SkyValue altValue) {
       return addErrorDependency(skyKey(name), altValue);
     }

     public TestFunction addErrorDependency(SkyKey key, SkyValue altValue) {
       deps.add(Pair.of(key, altValue));
       return this;
     }

     public TestFunction setConstantValue(SkyValue value) {
       Preconditions.checkState(this.computer == null);
       this.value = value;
       return this;
     }

     public TestFunction unsetConstantValue() {
       this.value = null;
       return this;
     }

     public TestFunction setComputedValue(ValueComputer computer) {
       Preconditions.checkState(this.value == null);
       this.computer = computer;
       return this;
     }

     public TestFunction unsetComputedValue() {
       this.computer = null;
       return this;
     }

     public TestFunction setBuilder(SkyFunction builder) {
       Preconditions.checkState(this.value == null);
       Preconditions.checkState(this.computer == null);
       Preconditions.checkState(deps.isEmpty());
       Preconditions.checkState(!hasTransientError);
       Preconditions.checkState(!hasError);
       Preconditions.checkState(warning == null);
       Preconditions.checkState(progress == null);
       this.builder = builder;
       return this;
     }

     public TestFunction setBuilderUnconditionally(SkyFunction builder) {
       this.builder = builder;
       return this;
     }

     public TestFunction setHasTransientError(boolean hasError) {
       this.hasTransientError = hasError;
       return this;
     }

     public TestFunction setHasError(boolean hasError) {
       // TODO(bazel-team): switch to an enum for hasError.
       this.hasError = hasError;
       return this;
     }

     public TestFunction setWarning(String warning) {
       this.warning = warning;
       return this;
     }

     public TestFunction setProgress(String info) {
       this.progress = info;
       return this;
     }

     public TestFunction setTag(String tag) {
       this.tag = tag;
       return this;
     }

     public TestFunction setPostable(Postable postable) {
       this.postable = postable;
       return this;
     }
   }

   public static ImmutableList<SkyKey> toSkyKeys(String... names) {
     ImmutableList.Builder<SkyKey> result = ImmutableList.builder();
     for (String element : names) {
       result.add(Key.create(element));
     }
     return result.build();
   }

   public static SkyKey toSkyKey(String name) {
     return toSkyKeys(name).get(0);
   }

   private class DelegatingFunction implements SkyFunction {
     @Override
     public SkyValue compute(SkyKey skyKey, Environment env) throws SkyFunctionException,
         InterruptedException {
       return getFunction().compute(skyKey, env);
     }

     @Nullable
     @Override
     public String extractTag(SkyKey skyKey) {
       return getFunction().extractTag(skyKey);
     }
   }

   public ImmutableMap<SkyFunctionName, ? extends SkyFunction> getSkyFunctionMap() {
     return ImmutableMap.copyOf(functionMap);
   }

   public void putSkyFunction(SkyFunctionName functionName, SkyFunction function) {
     functionMap.put(functionName, function);
   }

   /**
    * Simple value class that stores strings.
    */
   public static class StringValue implements SkyValue {
     protected final String value;

     public StringValue(String value) {
       this.value = value;
     }

     public String getValue() {
       return value;
     }

     @Override
     public boolean equals(Object o) {
       if (!(o instanceof StringValue)) {
         return false;
       }
       return value.equals(((StringValue) o).value);
     }

     @Override
     public int hashCode() {
       return value.hashCode();
     }

     @Override
     public String toString() {
       return "StringValue: " + getValue();
     }

     public static StringValue of(String string) {
       return new StringValue(string);
     }

     public static StringValue from(SkyValue skyValue) {
       assertThat(skyValue).isInstanceOf(StringValue.class);
       return (StringValue) skyValue;
     }
   }

   /** A StringValue that is also a NotComparableSkyValue. */
   public static class NotComparableStringValue extends StringValue
           implements NotComparableSkyValue {
     public NotComparableStringValue(String value) {
       super(value);
     }

     @Override
     public boolean equals(Object o) {
       throw new UnsupportedOperationException(value + " is incomparable - what are you doing?");
     }

     @Override
     public int hashCode() {
       throw new UnsupportedOperationException(value + " is incomparable - what are you doing?");
     }
   }

   /** An unshareable version of {@link StringValue}. */
   public static final class UnshareableStringValue extends StringValue {
     public UnshareableStringValue(String value) {
       super(value);
     }

     @Override
     public boolean dataIsShareable() {
       return false;
     }
   }

   /**
    * A callback interface to provide the value computation.
    */
   public interface ValueComputer {
     /** This is called when all the declared dependencies exist. It may request new dependencies. */
     SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env)
         throws InterruptedException;
   }

   public static final ValueComputer COPY = new ValueComputer() {
     @Override
     public SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env) {
       return Iterables.getOnlyElement(deps.values());
     }
   };

   public static final ValueComputer CONCATENATE = new ValueComputer() {
     @Override
     public SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env) {
       StringBuilder result = new StringBuilder();
       for (SkyValue value : deps.values()) {
         result.append(((StringValue) value).value);
       }
       return new StringValue(result.toString());
     }
   };

   public static ValueComputer formatter(final SkyKey key, final String format) {
     return new ValueComputer() {
       @Override
       public SkyValue compute(Map<SkyKey, SkyValue> deps, Environment env)
           throws InterruptedException {
         return StringValue.of(String.format(format, StringValue.from(deps.get(key)).getValue()));
       }
     };
   }

   @AutoCodec.VisibleForSerialization
   @AutoCodec
   static class Key extends AbstractSkyKey<String> {
     private static final Interner<Key> interner = BlazeInterners.newWeakInterner();

     private Key(String arg) {
       super(arg);
     }

     @AutoCodec.VisibleForSerialization
     @AutoCodec.Instantiator
     static Key create(String arg) {
       return interner.intern(new Key(arg));
     }

     @Override
     public SkyFunctionName functionName() {
       return SkyFunctionName.FOR_TESTING;
     }
   }

   @AutoCodec.VisibleForSerialization
   @AutoCodec
   static class NonHermeticKey extends AbstractSkyKey<String> {
     private static final Interner<NonHermeticKey> interner = BlazeInterners.newWeakInterner();

     private NonHermeticKey(String arg) {
       super(arg);
     }

     @AutoCodec.VisibleForSerialization
     @AutoCodec.Instantiator
     static NonHermeticKey create(String arg) {
       return interner.intern(new NonHermeticKey(arg));
     }

     @Override
     public SkyFunctionName functionName() {
       return FOR_TESTING_NONHERMETIC;
     }
   }

   private static final SkyFunctionName FOR_TESTING_NONHERMETIC =
       SkyFunctionName.createNonHermetic("FOR_TESTING_NONHERMETIC");
 }
	// Copyright 2014 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.
	package com.google.devtools.build.skyframe;

	import static com.google.common.truth.Truth.assertThat;

	import com.google.common.base.Preconditions;
	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.collect.ImmutableSet;
	import com.google.common.collect.Interner;
	import com.google.common.collect.Iterables;
	import com.google.devtools.build.lib.concurrent.BlazeInterners;
	import com.google.devtools.build.lib.events.Event;
	import com.google.devtools.build.lib.events.ExtendedEventHandler.Postable;
	import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
	import com.google.devtools.build.lib.util.Pair;
	import com.google.devtools.build.skyframe.SkyFunction.Environment;
	import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
	import java.util.HashMap;
	import java.util.LinkedHashMap;
	import java.util.LinkedHashSet;
	import java.util.Map;
	import java.util.Set;
	import javax.annotation.Nullable;

	/**
	* A helper class to create graphs and run skyframe tests over these graphs.
	*
	* <p>There are two types of values, computing values, which may not be set to a constant value,
	* and leaf values, which must be set to a constant value and may not have any dependencies.
	*
	* <p>Note that the value builder looks into the test values created here to determine how to
	* behave. However, skyframe will only re-evaluate the value and call the value builder if any of
	* its dependencies has changed. That means in order to change the set of dependencies of a value,
	* you need to also change one of its previous dependencies to force re-evaluation. Changing a
	* computing value does not mark it as modified.
	*/
	public class GraphTester {

	public static final SkyFunctionName NODE_TYPE = SkyFunctionName.FOR_TESTING;
	private final Map<SkyFunctionName, SkyFunction> functionMap = new HashMap<>();

	private final Map<SkyKey, TestFunction> values = new HashMap<>();
	private final Set<SkyKey> modifiedValues = new LinkedHashSet<>();

	public GraphTester() {
	functionMap.put(NODE_TYPE, new DelegatingFunction());
	functionMap.put(FOR_TESTING_NONHERMETIC, new DelegatingFunction());
	}

	public TestFunction getOrCreate(String name) {
	return getOrCreate(skyKey(name));
	}

	public TestFunction getOrCreate(SkyKey key) {
	return getOrCreate(key, false);
	}

	public TestFunction getOrCreate(SkyKey key, boolean markAsModified) {
	TestFunction result = values.get(key);
	if (result == null) {
	result = new TestFunction();
	values.put(key, result);
	} else if (markAsModified) {
	modifiedValues.add(key);
	}
	return result;
	}

	public TestFunction set(String key, SkyValue value) {
	return set(skyKey(key), value);
	}

	public TestFunction set(SkyKey key, SkyValue value) {
	return getOrCreate(key, true).setConstantValue(value);
	}

	public ImmutableSet<SkyKey> getModifiedValues() {
	return ImmutableSet.copyOf(modifiedValues);
	}

	public void clearModifiedValues() {
	modifiedValues.clear();
	}

	public SkyFunction getFunction() {
	return new SkyFunction() {
	@Override
	public SkyValue compute(SkyKey key, Environment env)
	throws SkyFunctionException, InterruptedException {
	TestFunction builder = values.get(key);
	Preconditions.checkState(builder != null, "No TestFunction for " + key);
	if (builder.builder != null) {
	return builder.builder.compute(key, env);
	}
	if (builder.warning != null) {
	env.getListener().handle(Event.warn(builder.warning));
	}
	if (builder.progress != null) {
	env.getListener().handle(Event.progress(builder.progress));
	}
	if (builder.postable != null) {
	env.getListener().post(builder.postable);
	}
	Map<SkyKey, SkyValue> deps = new LinkedHashMap<>();
	boolean oneMissing = false;
	for (Pair<SkyKey, SkyValue> dep : builder.deps) {
	SkyValue value;
	if (dep.second == null) {
	value = env.getValue(dep.first);
	} else {
	try {
	value = env.getValueOrThrow(dep.first, SomeErrorException.class);
	} catch (SomeErrorException e) {
	value = dep.second;
	}
	}
	if (value == null) {
	oneMissing = true;
	} else {
	deps.put(dep.first, value);
	}
	Preconditions.checkState(
	oneMissing == env.valuesMissing(), "%s %s %s", dep, value, env.valuesMissing());
	}
	if (env.valuesMissing()) {
	return null;
	}

	if (builder.hasTransientError) {
	throw new GenericFunctionException(new SomeErrorException(key.toString()),
	Transience.TRANSIENT);
	}
	if (builder.hasError) {
	throw new GenericFunctionException(new SomeErrorException(key.toString()),
	Transience.PERSISTENT);
	}

	if (builder.value != null) {
	return builder.value;
	}

	if (Thread.currentThread().isInterrupted()) {
	throw new InterruptedException(key.toString());
	}

	return builder.computer.compute(deps, env);
	}

	@Nullable
	@Override
	public String extractTag(SkyKey skyKey) {
	return values.get(skyKey).tag;
	}
	};
	}

	public static SkyKey skyKey(String key) {
	return Key.create(key);
	}

	public static NonHermeticKey nonHermeticKey(String key) {
	return NonHermeticKey.create(key);
	}

	/** A value in the testing graph that is constructed in the tester. */
	public static class TestFunction {
	// TODO(bazel-team): We could use a multiset here to simulate multi-pass dependency discovery.
	private final Set<Pair<SkyKey, SkyValue>> deps = new LinkedHashSet<>();
	private SkyValue value;
	private ValueComputer computer;
	private SkyFunction builder = null;

	private boolean hasTransientError;
	private boolean hasError;

	private String warning;
	private String progress;
	private Postable postable;

	private String tag;

	public TestFunction addDependency(String name) {
	return addDependency(skyKey(name));
	}

	public TestFunction addDependency(SkyKey key) {
	deps.add(Pair.<SkyKey, SkyValue>of(key, null));
	return this;
	}

	public TestFunction removeDependency(String name) {
	return removeDependency(skyKey(name));
	}

	public TestFunction removeDependency(SkyKey key) {
	deps.remove(Pair.<SkyKey, SkyValue>of(key, null));
	return this;
	}

	public TestFunction addErrorDependency(String name, SkyValue altValue) {
	return addErrorDependency(skyKey(name), altValue);
	}

	public TestFunction addErrorDependency(SkyKey key, SkyValue altValue) {
	deps.add(Pair.of(key, altValue));
	return this;
	}

	public TestFunction setConstantValue(SkyValue value) {
	Preconditions.checkState(this.computer == null);
	this.value = value;
	return this;
	}

	public TestFunction unsetConstantValue() {
	this.value = null;
	return this;
	}

	public TestFunction setComputedValue(ValueComputer computer) {
	Preconditions.checkState(this.value == null);
	this.computer = computer;
	return this;
	}

	public TestFunction unsetComputedValue() {
	this.computer = null;
	return this;
	}

	public TestFunction setBuilder(SkyFunction builder) {
	Preconditions.checkState(this.value == null);
	Preconditions.checkState(this.computer == null);
	Preconditions.checkState(deps.isEmpty());
	Preconditions.checkState(!hasTransientError);
	Preconditions.checkState(!hasError);
	Preconditions.checkState(warning == null);
	Preconditions.checkState(progress == null);
	this.builder = builder;
	return this;
	}

	public TestFunction setBuilderUnconditionally(SkyFunction builder) {
	this.builder = builder;
	return this;
	}

	public TestFunction setHasTransientError(boolean hasError) {
	this.hasTransientError = hasError;
	return this;
	}

	public TestFunction setHasError(boolean hasError) {
	// TODO(bazel-team): switch to an enum for hasError.
	this.hasError = hasError;
	return this;
	}

	public TestFunction setWarning(String warning) {
	this.warning = warning;
	return this;
	}

	public TestFunction setProgress(String info) {
	this.progress = info;
	return this;
	}

	public TestFunction setTag(String tag) {
	this.tag = tag;
	return this;
	}

	public TestFunction setPostable(Postable postable) {
	this.postable = postable;
	return this;
	}
	}

	public static ImmutableList<SkyKey> toSkyKeys(String... names) {
	ImmutableList.Builder<SkyKey> result = ImmutableList.builder();
	for (String element : names) {
	result.add(Key.create(element));
	}
	return result.build();
	}

	public static SkyKey toSkyKey(String name) {
	return toSkyKeys(name).get(0);
	}

	private class DelegatingFunction implements SkyFunction {
	@Override
	public SkyValue compute(SkyKey skyKey, Environment env) throws SkyFunctionException,
	InterruptedException {
	return getFunction().compute(skyKey, env);
	}

	@Nullable
	@Override
	public String extractTag(SkyKey skyKey) {
	return getFunction().extractTag(skyKey);
	}
	}

	public ImmutableMap<SkyFunctionName, ? extends SkyFunction> getSkyFunctionMap() {
	return ImmutableMap.copyOf(functionMap);
	}

	public void putSkyFunction(SkyFunctionName functionName, SkyFunction function) {
	functionMap.put(functionName, function);
	}

	/**
	* Simple value class that stores strings.
	*/
	public static class StringValue implements SkyValue {
	protected final String value;

	public StringValue(String value) {
	this.value = value;
	}

	public String getValue() {
	return value;
	}

	@Override
	public boolean equals(Object o) {
	if (!(o instanceof StringValue)) {
	return false;
	}
	return value.equals(((StringValue) o).value);
	}

	@Override
	public int hashCode() {
	return value.hashCode();
	}

	@Override
	public String toString() {
	return "StringValue: " + getValue();
	}

	public static StringValue of(String string) {
	return new StringValue(string);
	}

	public static StringValue from(SkyValue skyValue) {
	assertThat(skyValue).isInstanceOf(StringValue.class);
	return (StringValue) skyValue;
	}
	}

	/** A StringValue that is also a NotComparableSkyValue. */
	public static class NotComparableStringValue extends StringValue
	implements NotComparableSkyValue {
	public NotComparableStringValue(String value) {
	super(value);
	}

	@Override
	public boolean equals(Object o) {
	throw new UnsupportedOperationException(value + " is incomparable - what are you doing?");
	}

	@Override
	public int hashCode() {
	throw new UnsupportedOperationException(value + " is incomparable - what are you doing?");
	}
	}

	/** An unshareable version of {@link StringValue}. */
	public static final class UnshareableStringValue extends StringValue {
	public UnshareableStringValue(String value) {
	super(value);
	}

	@Override
	public boolean dataIsShareable() {
	return false;
	}
	}

	/**
	* A callback interface to provide the value computation.
	*/
	public interface ValueComputer {
	/** This is called when all the declared dependencies exist. It may request new dependencies. */
	SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env)
	throws InterruptedException;
	}

	public static final ValueComputer COPY = new ValueComputer() {
	@Override
	public SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env) {
	return Iterables.getOnlyElement(deps.values());
	}
	};

	public static final ValueComputer CONCATENATE = new ValueComputer() {
	@Override
	public SkyValue compute(Map<SkyKey, SkyValue> deps, SkyFunction.Environment env) {
	StringBuilder result = new StringBuilder();
	for (SkyValue value : deps.values()) {
	result.append(((StringValue) value).value);
	}
	return new StringValue(result.toString());
	}
	};

	public static ValueComputer formatter(final SkyKey key, final String format) {
	return new ValueComputer() {
	@Override
	public SkyValue compute(Map<SkyKey, SkyValue> deps, Environment env)
	throws InterruptedException {
	return StringValue.of(String.format(format, StringValue.from(deps.get(key)).getValue()));
	}
	};
	}

	@AutoCodec.VisibleForSerialization
	@AutoCodec
	static class Key extends AbstractSkyKey<String> {
	private static final Interner<Key> interner = BlazeInterners.newWeakInterner();

	private Key(String arg) {
	super(arg);
	}

	@AutoCodec.VisibleForSerialization
	@AutoCodec.Instantiator
	static Key create(String arg) {
	return interner.intern(new Key(arg));
	}

	@Override
	public SkyFunctionName functionName() {
	return SkyFunctionName.FOR_TESTING;
	}
	}

	@AutoCodec.VisibleForSerialization
	@AutoCodec
	static class NonHermeticKey extends AbstractSkyKey<String> {
	private static final Interner<NonHermeticKey> interner = BlazeInterners.newWeakInterner();

	private NonHermeticKey(String arg) {
	super(arg);
	}

	@AutoCodec.VisibleForSerialization
	@AutoCodec.Instantiator
	static NonHermeticKey create(String arg) {
	return interner.intern(new NonHermeticKey(arg));
	}

	@Override
	public SkyFunctionName functionName() {
	return FOR_TESTING_NONHERMETIC;
	}
	}

	private static final SkyFunctionName FOR_TESTING_NONHERMETIC =
	SkyFunctionName.createNonHermetic("FOR_TESTING_NONHERMETIC");
	}