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, 25 insertions, 15 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java
index 2b339046e0..fe44617e02 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ASTFileLookupFunction.java
@@ -20,6 +20,9 @@ import com.google.devtools.build.lib.packages.CachingPackageLocator;
 import com.google.devtools.build.lib.packages.RuleClassProvider;
 import com.google.devtools.build.lib.pkgcache.PathPackageLocator;
 import com.google.devtools.build.lib.syntax.BuildFileAST;
+import com.google.devtools.build.lib.syntax.Mutability;
+import com.google.devtools.build.lib.syntax.Runtime;
+import com.google.devtools.build.lib.syntax.ValidationEnvironment;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.RootedPath;
@@ -113,26 +116,33 @@ public class ASTFileLookupFunction implements SkyFunction {
     if (lookupResult == null) {
       return null;
     }
-
-    BuildFileAST ast = null;
     if (!lookupResult.lookupSuccessful()) {
       return ASTFileLookupValue.noFile();
-    } else {
-      Path path = lookupResult.rootedPath().asPath();
-      // Skylark files end with bzl.
-      boolean parseAsSkylark = astFilePathFragment.getPathString().endsWith(".bzl");
-      try {
-        ast = parseAsSkylark
-            ? BuildFileAST.parseSkylarkFile(path, env.getListener(),
-                packageManager, ruleClassProvider.getSkylarkValidationEnvironment().clone())
-            : BuildFileAST.parseBuildFile(path, env.getListener(),
-                packageManager, false);
-      } catch (IOException e) {
+    }
+    BuildFileAST ast = null;
+    Path path = lookupResult.rootedPath().asPath();
+    // Skylark files end with bzl.
+    boolean parseAsSkylark = astFilePathFragment.getPathString().endsWith(".bzl");
+    try {
+      if (parseAsSkylark) {
+        try (Mutability mutability = Mutability.create("validate")) {
+            ast = BuildFileAST.parseSkylarkFile(path, env.getListener(),
+                packageManager, new ValidationEnvironment(
+                    ruleClassProvider.createSkylarkRuleClassEnvironment(
+                        mutability,
+                        env.getListener(),
+                        // the two below don't matter for extracting the ValidationEnvironment:
+                        /*astFileContentHashCode=*/null,
+                        /*importMap=*/null)
+                    .setupDynamic(Runtime.PKG_NAME, Runtime.NONE)));
+        }
+      } else {
+        ast = BuildFileAST.parseBuildFile(path, env.getListener(), packageManager, false);
+      }
+    } catch (IOException e) {
         throw new ASTLookupFunctionException(new ErrorReadingSkylarkExtensionException(
             e.getMessage()), Transience.TRANSIENT);
-      }
     }
-
     return ASTFileLookupValue.withFile(ast);
   }