resolved file: include the hash of the output tree

When reporting about the repository rules that were called, also report
a hash of the tree the rule generated. This allows, at least after the fact,
to verify that a repository rule actually produced the correct code.

Note that equality of the output hash is not a guarantee for reproducible
builds, as certain properties of the output tree, in particular owner,
are ignored. Still it is a good check to detect wrong use of a repository
rule.

Change-Id: Ic56509f8e0d0b4be9ce3335ade280f983fe77e6d
PiperOrigin-RevId: 205631855

2 files changed, 19 insertions, 12 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryResolvedEvent.java b/src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryResolvedEvent.java
index 2087f3cd00..47801f3cfb 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryResolvedEvent.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryResolvedEvent.java
@@ -21,6 +21,8 @@ import com.google.devtools.build.lib.packages.Info;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.Runtime;
+import com.google.devtools.build.lib.vfs.Path;
+import java.io.IOException;
 import java.util.Map;
 
 /**
@@ -31,6 +33,7 @@ public class RepositoryResolvedEvent implements ProgressLike {
   public static final String ORIGINAL_ATTRIBUTES = "original_attributes";
   public static final String RULE_CLASS = "rule_class";
   public static final String ATTRIBUTES = "attributes";
+  public static final String OUTPUT_TREE_HASH = "output_tree_hash";
   public static final String REPOSITORIES = "repositories";
 
   /**
@@ -47,7 +50,7 @@ public class RepositoryResolvedEvent implements ProgressLike {
    */
   private final Object resolvedInformation;
 
-  public RepositoryResolvedEvent(Rule rule, Info attrs, Object result) {
+  public RepositoryResolvedEvent(Rule rule, Info attrs, Path outputDirectory, Object result) {
     ImmutableMap.Builder<String, Object> builder = ImmutableMap.builder();
 
     String originalClass =
@@ -69,25 +72,27 @@ public class RepositoryResolvedEvent implements ProgressLike {
     ImmutableMap<String, Object> origAttr = origAttrBuilder.build();
     builder.put(ORIGINAL_ATTRIBUTES, origAttr);
 
+    ImmutableMap.Builder<String, Object> repositoryBuilder =
+        ImmutableMap.<String, Object>builder().put(RULE_CLASS, originalClass);
+
+    try {
+      repositoryBuilder.put(OUTPUT_TREE_HASH, outputDirectory.getDirectoryDigest());
+    } catch (IOException e) {
+      // Digest not available, but we still have to report that a repository rule
+      // was invoked. So we can do nothing, but ignore the event.
+    }
+
     if (result == Runtime.NONE) {
       // Rule claims to be already reproducible, so wants to be called as is.
       builder.put(
           REPOSITORIES,
-          ImmutableList.<Object>of(
-              ImmutableMap.<String, Object>builder()
-                  .put(RULE_CLASS, originalClass)
-                  .put(ATTRIBUTES, origAttr)
-                  .build()));
+          ImmutableList.<Object>of(repositoryBuilder.put(ATTRIBUTES, origAttr).build()));
     } else if (result instanceof Map) {
       // Rule claims that the returned (probably changed) arguments are a reproducible
       // version of itself.
       builder.put(
           REPOSITORIES,
-          ImmutableList.<Object>of(
-              ImmutableMap.<String, Object>builder()
-                  .put(RULE_CLASS, originalClass)
-                  .put(ATTRIBUTES, result)
-                  .build()));
+          ImmutableList.<Object>of(repositoryBuilder.put(ATTRIBUTES, result).build()));
     } else {
       // TODO(aehlig): handle strings specially to allow encodings of the former
       // values to be accepted as well.
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryFunction.java b/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryFunction.java
index 4c3611ba8d..a4131bdbc2 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryFunction.java
@@ -106,7 +106,9 @@ public class SkylarkRepositoryFunction extends RepositoryFunction {
             .handle(Event.info("Repository rule '" + rule.getName() + "' returned: " + retValue));
       }
       env.getListener()
-          .post(new RepositoryResolvedEvent(rule, skylarkRepositoryContext.getAttr(), retValue));
+          .post(
+              new RepositoryResolvedEvent(
+                  rule, skylarkRepositoryContext.getAttr(), outputDirectory, retValue));
     } catch (EvalException e) {
       if (e.getCause() instanceof RepositoryMissingDependencyException) {
         // A dependency is missing, cleanup and returns null