Replace ThreadLocal accumulator with cursor-based lookup in DeclarativeRecipe

PR openrewrite#6810 changed DeclarativeRecipe.accumulator from a plain field to
ThreadLocal to fix concurrent recipe runs overwriting each other's
accumulator. However, ThreadLocal values are lost when execution
resumes on a different thread after yielding.

The accumulator is already stored on the rootCursor by
ScanningRecipe.getAccumulator(), which is per-run and survives thread
switches. This change removes the redundant ThreadLocal storage and
instead resolves the accumulator from the rootCursor at visit time.

The PreconditionBellwether now defers precondition resolution to
visit time (when the rootCursor is available) rather than eagerly
resolving in a field initializer.

Author: pstreef

rewrite-core/src/main/java/org/openrewrite/config/DeclarativeRecipe.java

@@ -26,7 +26,6 @@
 import java.time.Duration;
 import java.util.*;
 import java.util.function.Function;
-import java.util.function.Supplier;
 
 import static java.util.Collections.emptyList;
 import static org.openrewrite.Validated.invalid;
@@ -161,16 +160,12 @@ private void initializeDeclarativeRecipe(DeclarativeRecipe declarativeRecipe, St
         }
     }
 
-    @JsonIgnore
-    private transient ThreadLocal<Accumulator> accumulator = new ThreadLocal<>();
-
     @Override
     public Accumulator getInitialValue(ExecutionContext ctx) {
         Accumulator acc = new Accumulator();
         for (Recipe precondition : preconditions) {
             registerNestedScanningRecipes(precondition, acc, ctx);
         }
-        accumulator.set(acc);
         return acc;
     }
 
@@ -212,6 +207,11 @@ public static class Accumulator {
         Map<Recipe, Object> recipeToAccumulator = new HashMap<>();
     }
 
+    @FunctionalInterface
+    interface PreconditionResolver {
+        TreeVisitor<?, ExecutionContext> resolve(Cursor rootCursor, ExecutionContext ctx);
+    }
+
     @Value
     @EqualsAndHashCode(callSuper = false)
     @RequiredArgsConstructor
@@ -222,27 +222,35 @@ static class PreconditionBellwether extends Recipe {
         String description = "Evaluates a precondition and makes that result available to the preconditions of other recipes. " +
                    "\"bellwether\", noun - One that serves as a leader or as a leading indicator of future trends.";
 
-        Supplier<TreeVisitor<?, ExecutionContext>> precondition;
+        PreconditionResolver precondition;
 
         @NonFinal
         transient boolean preconditionApplicable;
 
         @Override
         public TreeVisitor<?, ExecutionContext> getVisitor() {
             return new TreeVisitor<Tree, ExecutionContext>() {
-                final TreeVisitor<?, ExecutionContext> p = precondition.get();
+                @Nullable
+                TreeVisitor<?, ExecutionContext> p;
 
                 @Override
                 public boolean isAcceptable(SourceFile sourceFile, ExecutionContext ctx) {
-                    return p.isAcceptable(sourceFile, ctx);
+                    return resolve(ctx).isAcceptable(sourceFile, ctx);
                 }
 
                 @Override
                 public @Nullable Tree visit(@Nullable Tree tree, ExecutionContext ctx) {
-                    Tree t = p.visit(tree, ctx);
+                    Tree t = resolve(ctx).visit(tree, ctx);
                     preconditionApplicable = t != tree;
                     return tree;
                 }
+
+                private TreeVisitor<?, ExecutionContext> resolve(ExecutionContext ctx) {
+                    if (p == null) {
+                        p = precondition.resolve(getCursor(), ctx);
+                    }
+                    return p;
+                }
             };
         }
     }
@@ -495,36 +503,37 @@ public final List<Recipe> getRecipeList() {
             return recipeList;
         }
 
-        List<Supplier<TreeVisitor<?, ExecutionContext>>> andPreconditions = new ArrayList<>();
-        for (Recipe precondition : preconditions) {
-            andPreconditions.add(() -> orVisitors(precondition));
-        }
+        List<Recipe> preconditionsCopy = new ArrayList<>(preconditions);
         //noinspection unchecked
-        PreconditionBellwether bellwether = new PreconditionBellwether(Preconditions.and(andPreconditions.toArray(new Supplier[]{})));
+        PreconditionBellwether bellwether = new PreconditionBellwether((rootCursor, ctx) -> {
+            TreeVisitor<?, ExecutionContext>[] visitors = new TreeVisitor[preconditionsCopy.size()];
+            for (int i = 0; i < preconditionsCopy.size(); i++) {
+                visitors[i] = orVisitors(preconditionsCopy.get(i), rootCursor, ctx);
+            }
+            return Preconditions.and(visitors);
+        });
         List<Recipe> recipeListWithBellwether = new ArrayList<>(recipeList.size() + 1);
         recipeListWithBellwether.add(bellwether);
         recipeListWithBellwether.addAll(decorateWithPreconditionBellwether(bellwether, recipeList));
         return recipeListWithBellwether;
     }
 
-    private TreeVisitor<?, ExecutionContext> orVisitors(Recipe recipe) {
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    private TreeVisitor<?, ExecutionContext> orVisitors(Recipe recipe, Cursor rootCursor, ExecutionContext ctx) {
         List<TreeVisitor<?, ExecutionContext>> conditions = new ArrayList<>();
         if (recipe instanceof ScanningRecipe) {
-            //noinspection rawtypes
             ScanningRecipe scanning = (ScanningRecipe) recipe;
-            //noinspection unchecked
-            Accumulator acc = accumulator.get();
+            Accumulator acc = getAccumulator(rootCursor, ctx);
             conditions.add(scanning.getVisitor(acc != null ? acc.recipeToAccumulator.get(scanning) : null));
         } else {
             conditions.add(recipe.getVisitor());
         }
         for (Recipe r : recipe.getRecipeList()) {
-            conditions.add(orVisitors(r));
+            conditions.add(orVisitors(r, rootCursor, ctx));
         }
         if (conditions.size() == 1) {
             return conditions.get(0);
         }
-        //noinspection unchecked
         return Preconditions.or(conditions.toArray(new TreeVisitor[0]));
     }
 
@@ -607,16 +616,9 @@ private static class LazyLoadedRecipe extends Recipe {
         String description = "Recipe that is loaded lazily.";
     }
 
-    @Override
-    public void onComplete(ExecutionContext ctx) {
-        accumulator.remove();
-    }
-
     @Override
     public DeclarativeRecipe clone() {
-        DeclarativeRecipe cloned = (DeclarativeRecipe) super.clone();
-        cloned.accumulator = new ThreadLocal<>();
-        return cloned;
+        return (DeclarativeRecipe) super.clone();
     }
 
     @Override