From 4498dc13d44e213aa70dbe615a4770fbf039ce6d Mon Sep 17 00:00:00 2001
From: Seyon Sivarajah <seyon.sivarajah@quantinuum.com>
Date: Wed, 25 Jun 2025 13:41:48 +0100
Subject: [PATCH] feat: use `core.` prefix for metadata keys

---
 guppylang/engine.py            | 12 ++++++++++--
 tests/test_version_metadata.py | 19 ++++++++++++++++---
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/guppylang/engine.py b/guppylang/engine.py
index 639b9c5e4..53bfa176a 100644
--- a/guppylang/engine.py
+++ b/guppylang/engine.py
@@ -1,4 +1,5 @@
 from collections import defaultdict
+from enum import Enum
 from types import FrameType
 
 import hugr.build.function as hf
@@ -58,6 +59,13 @@
 BUILTIN_DEFS = {defn.name: defn for defn in BUILTIN_DEFS_LIST}
 
 
+class CoreMetadataKeys(Enum):
+    """Core HUGR metadata keys used by Guppy."""
+
+    USED_EXTENSIONS = "core.used_extensions"
+    GENERATOR = "core.generator"
+
+
 class DefinitionStore:
     """Storage class holding references to all Guppy definitions created in the current
     interpreter session.
@@ -242,14 +250,14 @@ def compile(self, id: DefId) -> ModulePointer:
             hugr.std.int.INT_TYPES_EXTENSION,
             hugr.std.logic.EXTENSION,
         ]
-        graph.hugr.module_root.metadata["__used_extensions"] = [
+        graph.hugr.module_root.metadata[CoreMetadataKeys.USED_EXTENSIONS.value] = [
             {
                 "name": ext.name,
                 "version": str(ext.version),
             }
             for ext in all_used_extensions
         ]
-        graph.hugr.module_root.metadata["__generator"] = {
+        graph.hugr.module_root.metadata[CoreMetadataKeys.GENERATOR.value] = {
             "name": "guppylang",
             "version": guppylang.__version__,
         }
diff --git a/tests/test_version_metadata.py b/tests/test_version_metadata.py
index 2afabb970..5a4d7bc69 100644
--- a/tests/test_version_metadata.py
+++ b/tests/test_version_metadata.py
@@ -1,4 +1,8 @@
-from guppylang import guppy, __version__
+from sympy import use
+
+from guppylang import __version__, guppy
+from guppylang.engine import CoreMetadataKeys
+
 
 def test_metadata():
     @guppy
@@ -6,5 +10,14 @@ def foo() -> None:
         pass
 
     hugr = foo.compile().module
-    assert hugr.module_root.metadata["__generator"]["name"] == "guppylang"
-    assert hugr.module_root.metadata["__generator"]["version"] == __version__
+    meta = hugr.module_root.metadata
+    gen_key = CoreMetadataKeys.GENERATOR.value
+    assert meta[gen_key]["name"] == "guppylang"
+    assert meta[gen_key]["version"] == __version__
+
+    used_key = CoreMetadataKeys.USED_EXTENSIONS.value
+    used = meta[used_key]
+    assert len(used) > 0
+    assert all("name" in ext and "version" in ext for ext in used)
+    assert all(isinstance(ext["name"], str) for ext in used)
+    assert all(isinstance(ext["version"], str) for ext in used)