[GR-19220] Add Module#const_added

PullRequest: truffleruby/3924

Author: andrykonchin

CHANGELOG.md

@@ -36,6 +36,7 @@ Compatibility:
 * Add `timeout` argument to `Thread::SizedQueue#push` (#3039, @itarato).
 * Add `rb_syserr_new` function (@rwstauner).
 * Add `Enumerator#product` (#3039, @itarato).
+* Add `Module#const_added` (#3039,  @itarato).
 
 Performance:
 

spec/ruby/core/module/const_added_spec.rb

@@ -121,5 +121,40 @@ class SubClass
 
       ScratchPad.recorded.should == [line + 2, line + 4, line + 7, line + 11]
     end
+
+    it "is called when the constant is already assigned a value" do
+      ScratchPad.record []
+
+      mod = Module.new do
+        def self.const_added(name)
+          ScratchPad.record const_get(name)
+        end
+      end
+
+      mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+        TEST = 123
+      RUBY
+
+      ScratchPad.recorded.should == 123
+    end
+
+    it "records re-definition of existing constants" do
+      ScratchPad.record []
+
+      mod = Module.new do
+        def self.const_added(name)
+          ScratchPad << const_get(name)
+        end
+      end
+
+      -> {
+        mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+          TEST = 123
+          TEST = 456
+        RUBY
+      }.should complain(/warning: already initialized constant .+::TEST/)
+
+      ScratchPad.recorded.should == [123, 456]
+    end
   end
 end

spec/truffleruby.next-specs

@@ -33,6 +33,7 @@ spec/ruby/core/sizedqueue/append_spec.rb
 spec/ruby/core/sizedqueue/enq_spec.rb
 spec/ruby/core/sizedqueue/push_spec.rb
 
+spec/ruby/core/module/const_added_spec.rb
 spec/ruby/core/module/refinements_spec.rb
 spec/ruby/core/module/undefined_instance_methods_spec.rb
 spec/ruby/core/refinement/refined_class_spec.rb

src/main/java/org/truffleruby/RubyContext.java

@@ -159,6 +159,11 @@ public final class RubyContext {
     public long nativeArgv = 0L;
     public long nativeArgvLength = -1L;
 
+    // Whether or not a custom Module.const_added callback was defined.
+    // Optimization to avoid calling a default (empty) callback if there
+    // are no user-defined callbacks.
+    private volatile boolean constAddedDefined = false;
+
     private final AssumedValue<Boolean> warningCategoryDeprecated;
     private final AssumedValue<Boolean> warningCategoryExperimental;
 
@@ -444,7 +449,7 @@ private TruffleNFIPlatform createNativePlatform() {
 
     @TruffleBoundary
     public static Object send(Node currentNode, Object receiver, String methodName, Object... arguments) {
-        if (currentNode.isAdoptable()) {
+        if (currentNode != null && currentNode.isAdoptable()) {
             final EncapsulatingNodeReference callNodeRef = EncapsulatingNodeReference.getCurrent();
             final Node prev = callNodeRef.set(currentNode);
             try {
@@ -779,4 +784,12 @@ public void initializeMainScriptName(String mainScriptName) {
     public ImmutableRubyString getMainScriptName() {
         return this.mainScriptName;
     }
+
+    public boolean isConstAddedEverDefined() {
+        return constAddedDefined;
+    }
+
+    public void constAddedIsDefined() {
+        constAddedDefined = true;
+    }
 }

src/main/java/org/truffleruby/core/module/ModuleFields.java

@@ -457,6 +457,7 @@ public void setAutoloadConstant(RubyContext context, Node currentNode, String na
         context.getFeatureLoader().addAutoload(autoloadConstant);
     }
 
+    @TruffleBoundary
     private RubyConstant setConstantInternal(RubyContext context, Node currentNode, String name, Object value,
             boolean autoload) {
         checkFrozen(context, currentNode);
@@ -494,6 +495,11 @@ private RubyConstant setConstantInternal(RubyContext context, Node currentNode,
             invalidateConstantIncludedBy(name);
         }
 
+        if (context.isConstAddedEverDefined()) {
+            final RubySymbol nameSymbol = context.getLanguageSlow().getSymbol(name);
+            RubyContext.send(currentNode, rubyModule, "const_added", nameSymbol);
+        }
+
         return autoload ? newConstant : previous;
     }
 
@@ -571,6 +577,11 @@ public void addMethod(RubyContext context, Node currentNode, InternalMethod meth
                 }
             }
         }
+
+        // track if ever a custom Module.const_add callback is defined and ignore a default one
+        if (context.getCoreLibrary().isLoaded() && method.getName().equals("const_added")) {
+            RubyLanguage.getCurrentContext().constAddedIsDefined();
+        }
     }
 
     @TruffleBoundary

src/main/ruby/truffleruby/core/module.rb

@@ -61,6 +61,9 @@ def include?(mod)
     ancestors.any? { |m| Primitive.equal?(mod, m) }
   end
 
+  private def const_added(name)
+  end
+
   private def method_added(name)
   end