From 098cd2a6d3edc1725d4ce47d491e049ae729aef5 Mon Sep 17 00:00:00 2001
From: Ronald Tse <ronald.tse@ribose.com>
Date: Thu, 1 Oct 2026 06:12:32 +0800
Subject: [PATCH] =?UTF-8?q?fix:=20normalize=20capture-free=20blocks=20to?=
 =?UTF-8?q?=20empty=20arrays=20=E2=80=94=20the=20gate=20hits=20289/289?=
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The grammar consumes comments as whitespace, so a comment-only or
empty parallel/sequence body matches zero rule lines and .as folds
the capture-free block to a raw slice. The artifact's empty capture
is an array; the Normalizer now folds raw block values the same way.

Differential tree gate: 289/289 corpus maps byte-identical through
the .parg artifact (un-mar included via the bare-\\U accommodation).
---
 lib/interscript/isc/normalizer.rb         | 16 +++++++++++++++-
 spec/interscript/isc/node_adapter_spec.rb | 21 +++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/lib/interscript/isc/normalizer.rb b/lib/interscript/isc/normalizer.rb
index 8fe2dc71..a79bef04 100644
--- a/lib/interscript/isc/normalizer.rb
+++ b/lib/interscript/isc/normalizer.rb
@@ -64,7 +64,7 @@ def normalize_block(block)
         elsif block.key?(:tests)
           {tests: merge_tests(Array(block[:tests]))}
         elsif block.key?(:stage)
-          {stage_name: scalar(block[:stage_name]), stage: block[:stage]}
+          {stage_name: scalar(block[:stage_name]), stage: normalize_stage_items(block[:stage])}
         elsif block.key?(:target)
           {target: scalar(block[:target]), alias: scalar(block[:alias])}.compact
         else
@@ -72,6 +72,20 @@ def normalize_block(block)
         end
       end
 
+      # A capture-free block (empty or comment-only body — comments are
+      # consumed as whitespace) folds to a raw slice under .as; the .parg
+      # artifact's empty capture is an array. Match it.
+      def normalize_stage_items(items)
+        Array(items).map do |item|
+          if item.is_a?(Hash)
+            %i[parallel sequence].each do |k|
+              item = {k => []} if item.key?(k) && !item[k].is_a?(Array)
+            end
+          end
+          item
+        end
+      end
+
       # {field_name: {identifier: "authority"}, field_value: {string: [...]}}
       # becomes {authority: "BGN-PCGN"}.
       def normalize_meta_field(field)
diff --git a/spec/interscript/isc/node_adapter_spec.rb b/spec/interscript/isc/node_adapter_spec.rb
index bbc16731..c5886a60 100644
--- a/spec/interscript/isc/node_adapter_spec.rb
+++ b/spec/interscript/isc/node_adapter_spec.rb
@@ -421,3 +421,24 @@ def parse_and_adapt(src)
     expect(interp.call("чч")).to eq("ч")
   end
 end
+
+RSpec.describe "comment-only blocks" do
+  it "normalize to an empty block, matching the artifact tree" do
+    src = <<~ISC
+      system "t:a-b:C-D:1" {
+        metadata { name "T" }
+        stage main {
+          parallel {
+            # This is a comment
+          }
+        }
+      }
+    ISC
+    tree = Interscript::Isc::Parser.parse(src)
+    stage = tree[:system][:body].find { |b| b.is_a?(Hash) && b[:stage] }[:stage]
+    # The grammar consumes comments as whitespace; a capture-free block
+    # folds to a raw slice that must normalize to an empty array like
+    # the .parg artifact's empty capture.
+    expect(stage).to eq([{parallel: []}])
+  end
+end