Refactor Skylark Environment-s

Make Environment-s freezable: Introduce a class Mutability
as a revokable capability to mutate objects in an Environment.
For now, only Environment-s carry this capability.
Make sure that every Mutability is revoked in the same function that create...

This reinstates a change that previously rolled-back because it broke the
serializability of SkylarkLookupValue. Bad news: serializing it succeeds for the
wrong reason, because a SkylarkEnvironment was stored as a result (now an
Environment.Extension) that was Serializable but inherited its bindings from an Environment (now an Environment.BaseExtension) which wasn't Serializable.
Apparently, Java doesn't try to serialize the bindings then (or at least doesn't
error out when it fails), because these bindings map variable names to pretty
arbitrary objects, and a lot of those we find in practice aren't Serializable.
Thus the current code passes the same tests as the previous code, but obviously
the serialization is just as ineffective as it used to be.

--
MOS_MIGRATED_REVID=102776694

1 files changed, 19 insertions, 11 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/WorkspaceFileFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/WorkspaceFileFunction.java
index 30f0c6a027..ce45ca2155 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/WorkspaceFileFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/WorkspaceFileFunction.java
@@ -20,6 +20,7 @@ import com.google.devtools.build.lib.packages.PackageFactory;
 import com.google.devtools.build.lib.packages.RuleClassProvider;
 import com.google.devtools.build.lib.packages.WorkspaceFactory;
 import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.Mutability;
 import com.google.devtools.build.lib.syntax.ParserInputSource;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -62,18 +63,25 @@ public class WorkspaceFileFunction implements SkyFunction {
     Path repoWorkspace = workspaceRoot.getRoot().getRelative(workspaceRoot.getRelativePath());
     Builder builder = new Builder(repoWorkspace,
         packageFactory.getRuleClassProvider().getRunfilesPrefix());
-    WorkspaceFactory parser = new WorkspaceFactory(
-        builder, packageFactory.getRuleClassProvider(), installDir.getPathString());
-    parser.parse(ParserInputSource.create(
-        ruleClassProvider.getDefaultWorkspaceFile(), new PathFragment("DEFAULT.WORKSPACE")));
-    if (!workspaceFileValue.exists()) {
-      return new PackageValue(builder.build());
-    }
+    try (Mutability mutability = Mutability.create("workspace %s", repoWorkspace)) {
+      WorkspaceFactory parser =
+          new WorkspaceFactory(
+              builder,
+              packageFactory.getRuleClassProvider(),
+              mutability,
+              installDir.getPathString());
+      parser.parse(
+          ParserInputSource.create(
+              ruleClassProvider.getDefaultWorkspaceFile(), new PathFragment("DEFAULT.WORKSPACE")));
+      if (!workspaceFileValue.exists()) {
+        return new PackageValue(builder.build());
+      }
 
-    try {
-      parser.parse(ParserInputSource.create(repoWorkspace));
-    } catch (IOException e) {
-      throw new WorkspaceFileFunctionException(e, Transience.TRANSIENT);
+      try {
+        parser.parse(ParserInputSource.create(repoWorkspace));
+      } catch (IOException e) {
+        throw new WorkspaceFileFunctionException(e, Transience.TRANSIENT);
+      }
     }
 
     return new PackageValue(builder.build());