Add the concept of a "universal" configuration fragment, which all

configurations contain regardless of whether their rules explicitly
require it.

This is used to ensure all rules have BazelConfiguration. That
fragment supplies the path to the shell, which powers
BuildConfiguration.getShExecutable(), which powers any rule that
generates a SpawnAction.

Since SpawnActions are such a ubiquitous pattern we only want to
accelerate going forward, there's no point not to make this
automatically available to every rule.

--
MOS_MIGRATED_REVID=107786879

1 files changed, 21 insertions, 7 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
index f94d22fcb6..d95e95cb2e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/RuleContext.java
@@ -139,6 +139,7 @@ public final class RuleContext extends TargetContext
   private final Map<String, Attribute> aspectAttributes;
   private final BuildConfiguration hostConfiguration;
   private final ConfigurationFragmentPolicy configurationFragmentPolicy;
+  private final Class<? extends BuildConfiguration.Fragment> universalFragment;
   private final ErrorReporter reporter;
 
   private ActionOwner actionOwner;
@@ -148,11 +149,14 @@ public final class RuleContext extends TargetContext
 
   private RuleContext(Builder builder, ListMultimap<String, ConfiguredTarget> targetMap,
       ListMultimap<String, ConfiguredFilesetEntry> filesetEntryMap,
-      Set<ConfigMatchingProvider> configConditions, Map<String, Attribute> aspectAttributes) {
+      Set<ConfigMatchingProvider> configConditions,
+      Class<? extends BuildConfiguration.Fragment> universalFragment,
+      Map<String, Attribute> aspectAttributes) {
     super(builder.env, builder.rule, builder.configuration, builder.prerequisiteMap.get(null),
         builder.visibility);
     this.rule = builder.rule;
     this.configurationFragmentPolicy = builder.configurationFragmentPolicy;
+    this.universalFragment = universalFragment;
     this.targetMap = targetMap;
     this.filesetEntryMap = filesetEntryMap;
     this.configConditions = configConditions;
@@ -312,13 +316,10 @@ public final class RuleContext extends TargetContext
     return getConfiguration(config).getSkylarkFragmentNames();
   }
 
-  public ConfigurationFragmentPolicy getConfigurationFragment() {
-    return configurationFragmentPolicy;
-  }
-
   public <T extends Fragment> boolean isLegalFragment(
       Class<T> fragment, ConfigurationTransition config) {
-    return configurationFragmentPolicy.isLegalConfigurationFragment(fragment, config);
+    return fragment == universalFragment
+        || configurationFragmentPolicy.isLegalConfigurationFragment(fragment, config);
   }
 
   public <T extends Fragment> boolean isLegalFragment(Class<T> fragment) {
@@ -1227,6 +1228,7 @@ public final class RuleContext extends TargetContext
     private final AnalysisEnvironment env;
     private final Rule rule;
     private final ConfigurationFragmentPolicy configurationFragmentPolicy;
+    private Class<? extends BuildConfiguration.Fragment> universalFragment;
     private final BuildConfiguration configuration;
     private final BuildConfiguration hostConfiguration;
     private final PrerequisiteValidator prerequisiteValidator;
@@ -1255,7 +1257,7 @@ public final class RuleContext extends TargetContext
       ListMultimap<String, ConfiguredTarget> targetMap = createTargetMap();
       ListMultimap<String, ConfiguredFilesetEntry> filesetEntryMap =
           createFilesetEntryMap(rule, configConditions);
-      return new RuleContext(this, targetMap, filesetEntryMap, configConditions,
+      return new RuleContext(this, targetMap, filesetEntryMap, configConditions, universalFragment,
           aspectAttributes != null ? aspectAttributes : ImmutableMap.<String, Attribute>of());
     }
 
@@ -1290,6 +1292,18 @@ public final class RuleContext extends TargetContext
       return this;
     }
 
+    /**
+     * Sets the fragment that can be legally accessed even when not explicitly declared.
+     */
+    Builder setUniversalFragment(Class<? extends BuildConfiguration.Fragment> fragment) {
+      // TODO(bazel-team): Add this directly to ConfigurationFragmentPolicy, so we
+      // don't need separate logic specifically for checking this fragment. The challenge is
+      // that we need RuleClassProvider to figure out what this fragment is, and not every
+      // call state that creates ConfigurationFragmentPolicy has access to that.
+      this.universalFragment = fragment;
+      return this;
+    }
+
     private boolean validateFilesetEntry(FilesetEntry filesetEntry, ConfiguredTarget src) {
       if (src.getProvider(FilesetProvider.class) != null) {
         return true;