Revamp JavaToolchain:

- Rely on existing infrastructure to verify that attributes only contain a single artifact and that mandatory attributes are specified
- Add single artifact modifiers to attributes that need them
- Remove "final" modifiers from method variables (we don't use them in Blaze)
- Replace deprecated #add() with #addProvider()

Since this relies on existing infrastructure, I thought adding tests is redundant. I did test it manually, though, to be extra safe by testing what happens if these attributes contain an empty filegroup or a filegroup with multiple artifacts in it.

RELNOTES: None.
PiperOrigin-RevId: 158975017

1 files changed, 6 insertions, 0 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 02fb3e537b..e17ea79cec 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
@@ -1761,6 +1761,12 @@ public final class RuleContext extends TargetContext
         if (attribute == null) {
           continue;
         }
+
+        if (attribute.isSingleArtifact() && entry.getValue().size() > 1) {
+          attributeError(attribute.getName(), "must contain a single dependency");
+          continue;
+        }
+
         if (attribute.isSilentRuleClassFilter()) {
           Predicate<RuleClass> filter = attribute.getAllowedRuleClassesPredicate();
           for (ConfiguredTarget configuredTarget : entry.getValue()) {