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// 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.lib.rules.config;
import static com.google.devtools.build.lib.analysis.config.CoreOptionConverters.BUILD_SETTING_CONVERTERS;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.devtools.build.lib.actions.ActionConflictException;
import com.google.devtools.build.lib.analysis.AliasProvider;
import com.google.devtools.build.lib.analysis.BuildSettingProvider;
import com.google.devtools.build.lib.analysis.ConfiguredTarget;
import com.google.devtools.build.lib.analysis.FileProvider;
import com.google.devtools.build.lib.analysis.FilesToRunProvider;
import com.google.devtools.build.lib.analysis.LicensesProviderImpl;
import com.google.devtools.build.lib.analysis.RequiredConfigFragmentsProvider;
import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
import com.google.devtools.build.lib.analysis.RuleContext;
import com.google.devtools.build.lib.analysis.RuleErrorConsumer;
import com.google.devtools.build.lib.analysis.RunfilesProvider;
import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
import com.google.devtools.build.lib.analysis.config.BuildConfigurationValue;
import com.google.devtools.build.lib.analysis.config.BuildOptionDetails;
import com.google.devtools.build.lib.analysis.config.ConfigMatchingProvider;
import com.google.devtools.build.lib.analysis.config.FragmentOptions;
import com.google.devtools.build.lib.analysis.platform.ConstraintCollection;
import com.google.devtools.build.lib.analysis.platform.ConstraintValueInfo;
import com.google.devtools.build.lib.analysis.platform.PlatformProviderUtils;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.cmdline.PackageIdentifier;
import com.google.devtools.build.lib.cmdline.RepositoryName;
import com.google.devtools.build.lib.packages.AttributeMap;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
import com.google.devtools.build.lib.packages.Types;
import com.google.devtools.build.lib.rules.config.ConfigRuleClasses.ConfigSettingRule;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.common.options.OptionsParser;
import com.google.devtools.common.options.OptionsParsingException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import javax.annotation.Nullable;
/**
* Implementation for the config_setting rule.
*
* <p>This is a "pseudo-rule" in that its purpose isn't to generate output artifacts from input
* artifacts. Rather, it provides configuration context to rules that depend on it.
*/
public final class ConfigSetting implements RuleConfiguredTargetFactory {
@Override
@Nullable
public ConfiguredTarget create(RuleContext ruleContext)
throws InterruptedException, ActionConflictException {
AttributeMap attributes = NonconfigurableAttributeMapper.of(ruleContext.getRule());
Optional<String> likelyLabelInvalidSetting =
attributes.get(ConfigSettingRule.SETTINGS_ATTRIBUTE, Types.STRING_DICT).keySet().stream()
.filter(s -> s.startsWith("@") || s.startsWith("//") || s.startsWith(":"))
.findFirst();
if (likelyLabelInvalidSetting.isPresent()) {
ruleContext.attributeError(
ConfigSettingRule.SETTINGS_ATTRIBUTE,
String.format(
"'%s' is not a valid setting name, but appears to be a label. Did you mean to place"
+ " it in %s instead?",
likelyLabelInvalidSetting.get(), ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE));
return null;
}
// Get the built-in Blaze flag settings that match this rule.
ImmutableMultimap<String, String> nativeFlagSettings =
ImmutableMultimap.<String, String>builder()
.putAll(
attributes.get(ConfigSettingRule.SETTINGS_ATTRIBUTE, Types.STRING_DICT).entrySet())
.putAll(
attributes
.get(ConfigSettingRule.DEFINE_SETTINGS_ATTRIBUTE, Types.STRING_DICT)
.entrySet()
.stream()
.map(in -> Maps.immutableEntry("define", in.getKey() + "=" + in.getValue()))
.collect(ImmutableList.toImmutableList()))
.build();
// Get the user-defined flag settings that match this rule.
Map<Label, String> userDefinedFlagSettings =
attributes.get(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE, BuildType.LABEL_KEYED_STRING_DICT);
// Get the platform constraint settings that match this rule.
List<Label> constraintValueSettings =
attributes.get(ConfigSettingRule.CONSTRAINT_VALUES_ATTRIBUTE, BuildType.LABEL_LIST);
// Check that this config_setting contains at least one of {values, define_values,
// constraint_values}
if (!valuesAreSet(
nativeFlagSettings, userDefinedFlagSettings, constraintValueSettings, ruleContext)) {
return null;
}
BuildOptionDetails optionDetails = ruleContext.getConfiguration().getBuildOptionDetails();
boolean nativeFlagsMatch =
matchesConfig(nativeFlagSettings.entries(), optionDetails, ruleContext);
UserDefinedFlagMatch userDefinedFlags =
UserDefinedFlagMatch.fromAttributeValueAndPrerequisites(
userDefinedFlagSettings, optionDetails, ruleContext);
boolean constraintValuesMatch = constraintValuesMatch(ruleContext);
if (ruleContext.hasErrors()) {
return null;
}
ConfigMatchingProvider configMatcher =
ConfigMatchingProvider.create(
ruleContext.getLabel(),
nativeFlagSettings,
userDefinedFlags.getSpecifiedFlagValues(),
ImmutableSet.copyOf(constraintValueSettings),
ConfigMatchingProvider.MatchResult.merge(
userDefinedFlags.result(), nativeFlagsMatch && constraintValuesMatch));
return new RuleConfiguredTargetBuilder(ruleContext)
.addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
.addProvider(FileProvider.class, FileProvider.EMPTY)
.addProvider(FilesToRunProvider.class, FilesToRunProvider.EMPTY)
.addNativeDeclaredProvider(LicensesProviderImpl.EMPTY)
.addProvider(ConfigMatchingProvider.class, configMatcher)
.build();
}
@Override
public void addRuleImplSpecificRequiredConfigFragments(
RequiredConfigFragmentsProvider.Builder requiredFragments,
AttributeMap attributes,
BuildConfigurationValue configuration) {
// values
attributes
.get(ConfigSettingRule.SETTINGS_ATTRIBUTE, Types.STRING_DICT)
.forEach(
(optionName, value) -> {
if (optionName.equals("define")) {
int equalsIndex = value.indexOf('=');
requiredFragments.addDefine(
equalsIndex > 0 ? value.substring(0, equalsIndex) : value);
} else {
Class<? extends FragmentOptions> optionsClass =
configuration.getBuildOptionDetails().getOptionClass(optionName);
if (optionsClass != null) {
requiredFragments.addOptionsClass(optionsClass);
}
}
});
// define_values
requiredFragments.addDefines(
attributes.get(ConfigSettingRule.DEFINE_SETTINGS_ATTRIBUTE, Types.STRING_DICT).keySet());
// flag_values
requiredFragments.addStarlarkOptions(
attributes
.get(ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE, BuildType.LABEL_KEYED_STRING_DICT)
.keySet());
}
/**
* Returns true if all <code>constraint_values</code> settings are valid and match this
* configuration, false otherwise.
*
* <p>May generate rule errors on bad settings (e.g. wrong target types).
*/
private static boolean constraintValuesMatch(RuleContext ruleContext) {
List<ConstraintValueInfo> constraintValues = new ArrayList<>();
for (TransitiveInfoCollection dep :
ruleContext.getPrerequisites(ConfigSettingRule.CONSTRAINT_VALUES_ATTRIBUTE)) {
if (!PlatformProviderUtils.hasConstraintValue(dep)) {
ruleContext.attributeError(
ConfigSettingRule.CONSTRAINT_VALUES_ATTRIBUTE,
dep.getLabel() + " is not a constraint_value");
} else {
constraintValues.add(PlatformProviderUtils.constraintValue(dep));
}
}
if (ruleContext.hasErrors()) {
return false;
}
// The set of constraint_values in a config_setting should never contain multiple
// constraint_values that map to the same constraint_setting. This method checks if there are
// duplicates and records an error if so.
try {
ConstraintCollection.validateConstraints(constraintValues);
} catch (ConstraintCollection.DuplicateConstraintException e) {
ruleContext.ruleError(
ConstraintCollection.DuplicateConstraintException.formatError(e.duplicateConstraints()));
return false;
}
return ruleContext
.getToolchainContext()
.targetPlatform()
.constraints()
.containsAll(constraintValues);
}
/**
* Returns whether the given label falls under the {@code //tools} package (including subpackages)
* of the tools repository.
*/
@VisibleForTesting
static boolean isUnderToolsPackage(Label label, RepositoryName toolsRepository) {
PackageIdentifier packageId = label.getPackageIdentifier();
if (!packageId.getRepository().equals(toolsRepository)) {
return false;
}
try {
return packageId.getPackageFragment().subFragment(0, 1).equals(PathFragment.create("tools"));
} catch (IndexOutOfBoundsException e) {
// Top-level package (//).
return false;
}
}
/**
* User error when value settings can't be properly parsed.
*/
private static final String PARSE_ERROR_MESSAGE = "error while parsing configuration settings: ";
/**
* Check to make sure this config_setting contains and sets least one of {values, define_values,
* flag_value or constraint_values}.
*/
private static boolean valuesAreSet(
ImmutableMultimap<String, String> nativeFlagSettings,
Map<Label, String> userDefinedFlagSettings,
Iterable<Label> constraintValues,
RuleErrorConsumer errors) {
if (nativeFlagSettings.isEmpty()
&& userDefinedFlagSettings.isEmpty()
&& Iterables.isEmpty(constraintValues)) {
errors.ruleError(
String.format(
"Either %s, %s or %s must be specified and non-empty",
ConfigSettingRule.SETTINGS_ATTRIBUTE,
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
ConfigSettingRule.CONSTRAINT_VALUES_ATTRIBUTE));
return false;
}
return true;
}
/**
* Given a list of [flagName, flagValue] pairs for native Blaze flags, returns true if flagName ==
* flagValue for every item in the list under this configuration, false otherwise.
*/
private static boolean matchesConfig(
Collection<Map.Entry<String, String>> expectedSettings,
BuildOptionDetails options,
RuleContext ruleContext) {
// Rather than returning fast when we find a mismatch, continue looking at the other flags
// to check they're indeed valid flag specifications.
boolean foundMismatch = false;
for (Map.Entry<String, String> setting : expectedSettings) {
String optionName = setting.getKey();
String expectedRawValue = setting.getValue();
Class<? extends FragmentOptions> optionClass = options.getOptionClass(optionName);
if (optionClass == null) {
ruleContext.attributeError(
ConfigSettingRule.SETTINGS_ATTRIBUTE,
String.format(PARSE_ERROR_MESSAGE + "unknown option: '%s'", optionName));
foundMismatch = true;
continue;
}
OptionsParser parser;
try {
parser = OptionsParser.builder().optionsClasses(optionClass).build();
parser.parse("--" + optionName + "=" + expectedRawValue);
} catch (OptionsParsingException ex) {
ruleContext.attributeError(
ConfigSettingRule.SETTINGS_ATTRIBUTE, PARSE_ERROR_MESSAGE + ex.getMessage());
foundMismatch = true;
continue;
}
Object expectedParsedValue = parser.getOptions(optionClass).asMap().get(optionName);
if (!optionMatches(options, optionName, expectedParsedValue)) {
foundMismatch = true;
}
}
return !foundMismatch;
}
/**
* For single-value options, returns true iff the option's value matches the expected value.
*
* <p>For multi-value List options returns true iff any of the option's values matches the
* expected value(s). This means "--ios_multi_cpus=a --ios_multi_cpus=b --ios_multi_cpus=c"
* matches the expected conditions {'ios_multi_cpus': 'a' } and { 'ios_multi_cpus': 'b,c' } but
* not { 'ios_multi_cpus': 'd' }.
*
* <p>For multi-value Map options, returns true iff the last instance with the same key as the
* expected key has the same value. This means "--define foo=1 --define bar=2" matches { 'define':
* 'foo=1' }, but "--define foo=1 --define bar=2 --define foo=3" doesn't match. Note that the
* definition of --define states that the last instance takes precedence. Also note that there's
* no options-parsing support for multiple values in a single clause, e.g. { 'define':
* 'foo=1,bar=2' } expands to { "foo": "1,bar=2" }, not {"foo": 1, "bar": "2"}.
*/
private static boolean optionMatches(
BuildOptionDetails options, String optionName, Object expectedValue) {
Object actualValue = options.getOptionValue(optionName);
if (actualValue == null) {
return expectedValue == null;
// Single-value case:
} else if (!options.allowsMultipleValues(optionName)) {
return actualValue.equals(expectedValue);
}
// Multi-value case:
Preconditions.checkState(actualValue instanceof List);
Preconditions.checkState(expectedValue instanceof List);
List<?> actualList = (List<?>) actualValue;
List<?> expectedList = (List<?>) expectedValue;
if (actualList.isEmpty() || expectedList.isEmpty()) {
return actualList.isEmpty() && expectedList.isEmpty();
}
// Multi-value map:
if (actualList.get(0) instanceof Map.Entry) {
// The config_setting's expected value *must* be a single map entry (see method comments).
Object expectedListValue = Iterables.getOnlyElement(expectedList);
Map.Entry<?, ?> expectedEntry = (Map.Entry<?, ?>) expectedListValue;
for (Object elem : Lists.reverse(actualList)) {
Map.Entry<?, ?> actualEntry = (Map.Entry<?, ?>) elem;
if (actualEntry.getKey().equals(expectedEntry.getKey())) {
// Found a key match!
return actualEntry.getValue().equals(expectedEntry.getValue());
}
}
return false;
}
// Multi-value list:
return actualList.containsAll(expectedList);
}
private static final class UserDefinedFlagMatch {
private final ConfigMatchingProvider.MatchResult result;
private final ImmutableMap<Label, String> specifiedFlagValues;
private static final Joiner QUOTED_COMMA_JOINER = Joiner.on("', '");
private UserDefinedFlagMatch(
ConfigMatchingProvider.MatchResult result,
ImmutableMap<Label, String> specifiedFlagValues) {
this.result = result;
this.specifiedFlagValues = specifiedFlagValues;
}
/** Returns whether the specified flag values matched the actual flag values. */
public ConfigMatchingProvider.MatchResult result() {
return result;
}
/** Gets the specified flag values, with aliases converted to their original targets' labels. */
ImmutableMap<Label, String> getSpecifiedFlagValues() {
return specifiedFlagValues;
}
/** Groups aliases in the list of prerequisites by the target they point to. */
private static ListMultimap<Label, Label> collectAliases(
Iterable<? extends TransitiveInfoCollection> prerequisites) {
ImmutableListMultimap.Builder<Label, Label> targetsToAliases =
new ImmutableListMultimap.Builder<>();
for (TransitiveInfoCollection target : prerequisites) {
targetsToAliases.put(target.getLabel(), AliasProvider.getDependencyLabel(target));
}
return targetsToAliases.build();
}
/**
* The 'flag_values' attribute takes a label->string dictionary of feature flags and
* starlark-defined settings to their values in string form.
*
* @param attributeValue map of user-defined flag labels to their values as set in the
* 'flag_values' attribute
* @param optionDetails information about the configuration to match against
* @param ruleContext this rule's RuleContext
*/
static UserDefinedFlagMatch fromAttributeValueAndPrerequisites(
Map<Label, String> attributeValue,
BuildOptionDetails optionDetails,
RuleContext ruleContext) {
Map<Label, String> specifiedFlagValues = new LinkedHashMap<>();
boolean matches = true;
// Only configuration-dependent errors should be deferred.
ArrayList<String> deferredErrors = new ArrayList<>();
boolean foundDuplicate = false;
// Get the actual targets the 'flag_values' keys reference.
Iterable<? extends TransitiveInfoCollection> prerequisites =
ruleContext.getPrerequisites(ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE);
for (TransitiveInfoCollection target : prerequisites) {
Label actualLabel = target.getLabel();
Label specifiedLabel = AliasProvider.getDependencyLabel(target);
String specifiedValue =
maybeCanonicalizeLabel(attributeValue.get(specifiedLabel), target, ruleContext);
if (specifiedFlagValues.containsKey(actualLabel)) {
foundDuplicate = true;
}
specifiedFlagValues.put(actualLabel, specifiedValue);
if (target.satisfies(ConfigFeatureFlagProvider.REQUIRE_CONFIG_FEATURE_FLAG_PROVIDER)) {
// config_feature_flag
ConfigFeatureFlagProvider provider = ConfigFeatureFlagProvider.fromTarget(target);
if (!provider.isValidValue(specifiedValue)) {
// This is a configuration-independent error on the attributes of config_setting.
// So, is appropriate to error immediately.
ruleContext.attributeError(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
String.format(
"error while parsing user-defined configuration values: "
+ "'%s' is not a valid value for '%s'",
specifiedValue, specifiedLabel));
matches = false;
continue;
}
if (!Strings.isNullOrEmpty(provider.getError())) {
deferredErrors.add(provider.getError());
continue;
} else if (!provider.getFlagValue().equals(specifiedValue)) {
matches = false;
}
} else if (target.satisfies(BuildSettingProvider.REQUIRE_BUILD_SETTING_PROVIDER)) {
// build setting
BuildSettingProvider provider = target.getProvider(BuildSettingProvider.class);
Object configurationValue;
if (optionDetails.getOptionValue(provider.getLabel()) != null) {
configurationValue = optionDetails.getOptionValue(provider.getLabel());
} else {
configurationValue = provider.getDefaultValue();
}
Object convertedSpecifiedValue;
try {
// We don't need to supply a base package or repo mapping for the conversion here,
// because `specifiedValue` is already canonicalized.
convertedSpecifiedValue =
BUILD_SETTING_CONVERTERS
.get(provider.getType())
.convert(specifiedValue, /*conversionContext=*/ null);
} catch (OptionsParsingException e) {
// This is a configuration-independent error on the attributes of config_setting.
// So, is appropriate to error immediately.
ruleContext.attributeError(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
String.format(
"error while parsing user-defined configuration values: "
+ "'%s' cannot be converted to %s type %s",
specifiedValue, specifiedLabel, provider.getType()));
matches = false;
continue;
}
if (configurationValue instanceof List) {
// If the build_setting is a list it's either an allow-multiple string-typed build
// setting or a string_list-typed build setting. We use the same semantics as for
// multi-value native flags: if *any* entry in the list matches the config_setting's
// expected entry, it's a match. In other words,
// config_setting(flag_values {"//foo": "bar"} matches //foo=["bar", "baz"].
// If this is an allow-multiple build setting, the converter will have converted the
// config settings value to a singular object, if it's a string_list build setting the
// converter will have converted it to a list.
Iterable<?> specifiedValueAsIterable =
provider.allowsMultiple()
? ImmutableList.of(convertedSpecifiedValue)
: (Iterable<?>) convertedSpecifiedValue;
if (Iterables.size(specifiedValueAsIterable) != 1) {
// This is a configuration-independent error on the attributes of config_setting.
// So, is appropriate to error immediately.
ruleContext.attributeError(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
String.format(
"\"%s\" not a valid value for flag %s. Only single, exact values are"
+ " allowed. If you want to match multiple values, consider Skylib's "
+ "selects.config_setting_group",
specifiedValue, specifiedLabel));
matches = false;
} else if (!((List<?>) configurationValue)
.contains(Iterables.getOnlyElement(specifiedValueAsIterable))) {
matches = false;
}
} else if (!configurationValue.equals(convertedSpecifiedValue)) {
matches = false;
}
} else {
// This should be configuration-independent error on the attributes of config_setting.
// So, is appropriate to error immediately.
// 'Should' b/c the underlying flag rule COULD change providers based on configuration;
// however, this is HIGHLY irregular.
ruleContext.attributeError(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
String.format(
"error while parsing user-defined configuration values: "
+ "%s keys must be build settings or feature flags and %s is not",
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE, specifiedLabel));
matches = false;
}
}
// attributeValue is the source of the prerequisites in prerequisites, so the final map built
// from iterating over prerequisites should always be the same size, barring duplicates.
assert foundDuplicate || attributeValue.size() == specifiedFlagValues.size();
if (foundDuplicate) {
ListMultimap<Label, Label> aliases = collectAliases(prerequisites);
for (Label actualLabel : aliases.keySet()) {
List<Label> aliasList = aliases.get(actualLabel);
if (aliasList.size() > 1) {
// This is a configuration-independent error on the attributes of config_setting.
// So, is appropriate to error immediately.
ruleContext.attributeError(
ConfigSettingRule.FLAG_SETTINGS_ATTRIBUTE,
String.format(
"flag '%s' referenced multiple times as ['%s']",
actualLabel, QUOTED_COMMA_JOINER.join(aliasList)));
}
}
matches = false;
}
if (!deferredErrors.isEmpty()) {
return new UserDefinedFlagMatch(
ConfigMatchingProvider.MatchResult.InError.create(Joiner.on(", ").join(deferredErrors)),
ImmutableMap.copyOf(specifiedFlagValues));
}
return new UserDefinedFlagMatch(
ConfigMatchingProvider.MatchResult.create(matches),
ImmutableMap.copyOf(specifiedFlagValues));
}
}
/**
* Given a 'flag_values = {"//ref:to:flagTarget": "expectedValue"}' pair, if expectedValue is a
* relative label (e.g. ":sometarget") and flagTarget's value(s) are label-typed, returns an
* absolute form of the label under the config_setting's package. Else returns the original value
* unchanged.
*
* <p>This lets config_setting use relative labels to match against the actual values, which are
* already represented in absolute form.
*
* <p>The value is returned as a string because it's subsequently fed through the flag's type
* converter (which maps a string to the final type). Invalid labels are treated no differently
* (they don't trigger special errors here) because the type converter will also handle that.
*
* @param expectedValue the raw value the config_setting expects
* @param flagTarget the target of the flag whose value is being checked
* @param ruleContext this rule's RuleContext
*/
private static String maybeCanonicalizeLabel(
String expectedValue, TransitiveInfoCollection flagTarget, RuleContext ruleContext) {
if (!flagTarget.satisfies(BuildSettingProvider.REQUIRE_BUILD_SETTING_PROVIDER)) {
return expectedValue;
}
if (!BuildType.isLabelType(flagTarget.getProvider(BuildSettingProvider.class).getType())) {
return expectedValue;
}
try {
return Label.parseWithPackageContext(expectedValue, ruleContext.getPackageContext())
.getUnambiguousCanonicalForm();
} catch (LabelSyntaxException e) {
// Swallow this: the subsequent type conversion already checks for this.
return expectedValue;
}
}
}