// Copyright 2017 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.lib.analysis;
import static com.google.common.truth.Truth.assertThat;
import com.google.devtools.build.lib.analysis.util.BuildViewTestBase;
import com.google.devtools.build.lib.skyframe.BuildConfigurationValue;
import com.google.devtools.build.lib.skyframe.SkyframeBuildView;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
/**
* Tests for {@link OutputFileConfiguredTarget}.
*/
@RunWith(JUnit4.class)
public class OutputFileConfiguredTargetTest extends BuildViewTestBase {
@Test
public void generatingRuleIsCorrect() throws Exception {
scratch.file("foo/BUILD",
"genrule(",
" name='generating_rule', ",
" cmd = 'echo hi > $@',",
" srcs = [],",
" outs = ['generated.source'])");
update("//foo:generating_rule");
OutputFileConfiguredTarget generatedSource = (OutputFileConfiguredTarget)
getConfiguredTarget("//foo:generated.source", getHostConfiguration());
assertThat(generatedSource.getGeneratingRule())
.isSameAs(getConfiguredTarget("//foo:generating_rule", getHostConfiguration()));
}
/**
* This regression-tests the fix for a bug in which Bazel could crash with a NullPointerException
* when two builds were invoked with different configurations because an output file ended up
* unexpectedly having a null generating rule.
*
* <p>The reasons for this are subtle and complex. In short, the bug only happens when
* --experimental_dynamic_configs=off and BuildConfiguration.equals provides value equality.
*
* <p>In that scenario, when we call {@code bazel build //foo:gen1 --copt a=b}, Bazel creates a
* host configuration H1 for this build that attaches to {@code
* //foo:host_generated_file_producer} (which is the generator of {@code host_src1.cc}).
*
* <p>When we then call {@code bazel build //foo:gen2 --copt a=c}, the options have changed so
* Bazel clears all configurations and configured targets. This includes the host configuration,
* even though - importantly - none of its options have changed. So Bazel uses a new host config
* H2 that's value-equal to H1 (but not reference-equal) and assigns it to {@code host_src2.cc}.
*
* <p>Here's the problem: during configured target analysis, Bazel creates the configured target
* <host_src2.cc, H2>, then requests from Skyframe the dependency with SkyKey
* <host_generated_file_producer, H2>. But Skyframe uses an interner to reference-collapse
* equivalent keys (SkyKey.SKY_KEY_INTERNER}). And that doesn't get cleared between builds. So
* the actual SkyKey used is <host_generated_file_producer, H1>, which produces a ConfiguredTarget
* with config=H1. This breaks {@link TargetContext#findDirectPrerequisite}, which output files
* use to find their generating rules. That method looks for
* {@code label.equals("host_generated_file_producer")} and {@code config == H2}, which finds
* no match so returns a null reference.
*
* <p>When configs only use reference equality, the problem goes away because the interner can no
* longer safely merge H1 and H2. An alternative fix might be to change
* {@link TargetContext#findDirectPrerequisite} to check {@code config.equals(H2)} instead of
* {@code config == H2}. But this isn't really safe because static configs embed references to
* other configs in their transition table. So returning H1 when you expect H2 creates the
* possibility of "leaking out" to the wrong configuration during a transition, even if H1 and H2
* have the same exact build options.
*
* <p>All of these problems go away with dynamic configurations. This is for two reasons: 1)
* dynamic configs don't embed transition tables, so "leaking out" is no longer possible. And
* 2) a dynamic config is evaluated through Skyframe keyed on its BuildOptions, so semantic
* equality implies reference equality anyway, 2 may change in the future, but if/when it does
* this test should reliably fail so appropriate measures can be taken.
*/
@Test
public void regressionTestForStaticConfigsWithValueEquality() throws Exception {
scratch.file("foo/BUILD",
"genrule(",
" name = 'host_generated_file_producer',",
" srcs = [],",
" outs = [",
" 'host_src1.cc',",
" 'host_src2.cc',",
" ],",
" cmd = 'echo hi > $(location host_src1.cc); echo hi > $(location host_src2.cc)')",
"",
"cc_binary(",
" name = 'host_generated_file_consumer1',",
" srcs = ['host_src1.cc'])",
"",
"cc_binary(",
" name = 'host_generated_file_consumer2',",
" srcs = ['host_src2.cc'])",
"",
"genrule(",
" name = 'gen1',",
" srcs = [],",
" outs = ['gen1.out'],",
" cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer1'])",
"",
"genrule(",
" name = 'gen2',",
" srcs = [],",
" outs = ['gen2.out'],",
" cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer2'])"
);
useConfiguration("--copt", "a=b");
update("//foo:gen1");
useConfiguration("--copt", "a=c");
update("//foo:gen2");
OutputFileConfiguredTarget hostSrc2 = (OutputFileConfiguredTarget)
getConfiguredTarget("//foo:host_src2.cc", getHostConfiguration());
assertThat(hostSrc2.getGeneratingRule()).isNotNull();
}
/**
* Dynamic configurations maintain a host configuration cache that stores configurations
* instantiated outside of Skyframe. We shouldn't, in general, instantiate configurations
* outside of {@link BuildConfigurationValue}. But in this specific case Bazel performance
* suffers through the Skyframe interface and maintaining a local cache is much faster.
* See {@link SkyframeBuildView} for details.
*
* <p>One consequence of this is that requesting a config that would be a Skyframe cache hit
* can still produce a distinct instance. Meaning you can get cases where {@code
* config1.equals(config2) && config1 != config2}.
*
* <p>This test checks for such a case: perform three consecutive Bazel builds. The first builds
* with default options, producing top-level host config H1 and configured target
* <host_generated_file_producer, H1>. The second builds with {@code --host_copt=a=b},
* producing host config H2 (and clearing the top-level host config cache since the host config
* changed). The third builds back with default options. This once again clears the host config
* cache, since the host config changed again. So that cache creates a new config H3 where
* H3.equals(H1) and instantiates new configured target <host_src3.cc, H3>. It then requests
* dependency <host_generated_file_producer, H3> from Skyframe, but the Skyframe SkyKey interner
* reduces this to the previously seen <host_generated_file_producer, H1> and returns that
* instead.
*
* <p>This produces the expected scenario where the output file's config is value-equal but not
* reference-equal to its generating rule's config.
*/
@Test
public void dynamicConfigsWithHostConfigSwitch() throws Exception {
scratch.file("foo/BUILD",
"genrule(",
" name = 'host_generated_file_producer',",
" srcs = [],",
" outs = [",
" 'host_src1.cc',",
" 'host_src2.cc',",
" 'host_src3.cc',",
" ],",
" cmd = 'echo hi > $(location host_src1.cc); echo hi > $(location host_src2.cc); "
+ "echo hi > $(location host_src3.cc)')",
"",
"cc_binary(name = 'host_generated_file_consumer1', srcs = ['host_src1.cc'])",
"cc_binary(name = 'host_generated_file_consumer2', srcs = ['host_src2.cc'])",
"cc_binary(name = 'host_generated_file_consumer3', srcs = ['host_src3.cc'])",
"",
"genrule(name = 'gen1', srcs = [], outs = ['gen1.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer1'])",
"genrule(name = 'gen2', srcs = [], outs = ['gen2.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer2'])",
"genrule(name = 'gen3', srcs = [], outs = ['gen3.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer3'])");
String dynamicConfigsMode = "--experimental_dynamic_configs=notrim";
useConfiguration(dynamicConfigsMode);
update("//foo:gen1");
useConfiguration(dynamicConfigsMode, "--host_copt", "a=b");
update("//foo:gen2");
useConfiguration(dynamicConfigsMode);
update("//foo:gen3");
OutputFileConfiguredTarget hostSrc3 = (OutputFileConfiguredTarget)
getConfiguredTarget("//foo:host_src3.cc", getHostConfiguration());
TransitiveInfoCollection hostGeneratedFileConsumer3 = hostSrc3.getGeneratingRule();
assertThat(hostSrc3.getConfiguration())
.isEqualTo(hostGeneratedFileConsumer3.getConfiguration());
// TODO(gregce): enable below for Bazel tests, which for some reason realize the same instance
// assertThat(hostSrc3.getConfiguration())
// .isNotSameAs(hostGeneratedFileConsumer3.getConfiguration());
}
}