From fe1af87934ea305fd610e43d6e0b0d340dee24ba Mon Sep 17 00:00:00 2001
From: Tristan Simas <tristan.simas@mail.mcgill.ca>
Date: Mon, 12 Oct 2026 00:34:53 -0400
Subject: [PATCH 1/2] WIP: one factory and one formatter per type

---
 src/formbridge/forms/parameter_info_types.py  |  6 ++++++
 src/formbridge/protocols/preview_formatter.py |  6 ++++++
 tests/test_preview_formatter_registry.py      | 15 +++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/src/formbridge/forms/parameter_info_types.py b/src/formbridge/forms/parameter_info_types.py
index c1e713f..6ac6081 100644
--- a/src/formbridge/forms/parameter_info_types.py
+++ b/src/formbridge/forms/parameter_info_types.py
@@ -71,6 +71,12 @@ def register(
                 "Inline dataclass widgets can only be registered for dataclass types; "
                 f"got {dataclass_type!r}."
             )
+        registered = cls._factories.get(dataclass_type)
+        if registered is not None and registered is not widget_factory:
+            raise ValueError(
+                f"{dataclass_type.__qualname__} already has an inline widget factory "
+                f"({registered!r}); it cannot also use {widget_factory!r}."
+            )
         cls._factories[dataclass_type] = widget_factory
 
     @classmethod
diff --git a/src/formbridge/protocols/preview_formatter.py b/src/formbridge/protocols/preview_formatter.py
index ddf4475..fbcdab1 100644
--- a/src/formbridge/protocols/preview_formatter.py
+++ b/src/formbridge/protocols/preview_formatter.py
@@ -39,6 +39,12 @@ def register(
             config_type: Config class to format
             formatter: Formatter function taking (config, field_name) -> str
         """
+        registered = cls._formatters.get(config_type)
+        if registered is not None and registered is not formatter:
+            raise ValueError(
+                f"{config_type.__qualname__} already has a preview formatter "
+                f"({registered!r}); it cannot also use {formatter!r}."
+            )
         cls._formatters[config_type] = formatter
 
     @classmethod
diff --git a/tests/test_preview_formatter_registry.py b/tests/test_preview_formatter_registry.py
index 66f0afe..007adb5 100644
--- a/tests/test_preview_formatter_registry.py
+++ b/tests/test_preview_formatter_registry.py
@@ -55,3 +55,18 @@ class BaseConfig:
     )
 
     assert PreviewFormatterRegistry.format_field(lazy_type(), "value") == "base"
+
+
+def test_preview_formatter_registration_rejects_a_second_formatter_for_one_type() -> None:
+    class OnceConfig:
+        pass
+
+    def formatter(_config: object, field_name: str) -> str:
+        return f"first:{field_name}"
+
+    PreviewFormatterRegistry.register(OnceConfig, formatter)
+    PreviewFormatterRegistry.register(OnceConfig, formatter)
+
+    with pytest.raises(ValueError, match="OnceConfig already has a preview formatter"):
+        PreviewFormatterRegistry.register(OnceConfig, lambda _config, _field_name: "second")
+    assert PreviewFormatterRegistry.format_field(OnceConfig(), "value") == "first:value"

From f901e0fcc73038420c0cf386386f9a92b8155151 Mon Sep 17 00:00:00 2001
From: Tristan Simas <tristan.simas@mail.mcgill.ca>
Date: Mon, 12 Oct 2026 08:39:15 -0400
Subject: [PATCH 2/2] 0.1.3: one inline-widget factory and one preview
 formatter per type; require metaclass-registry 0.4

Raises lower bounds to objectstate 3.0.1 and zmqruntime 0.6.4.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 CHANGELOG.md               | 13 +++++++++++++
 pyproject.toml             |  6 +++---
 requirements-ci.txt        |  2 +-
 src/formbridge/__init__.py |  2 +-
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bee7eff..58991b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,18 @@
 # Changelog
 
+## 0.1.3
+
+Requires `metaclass-registry>=0.4.0`, `objectstate>=3.0.1,<4` and
+`zmqruntime>=0.6.4,<0.7`.
+
+Changed:
+
+- A type has one inline-widget factory and one preview formatter.
+  `PreviewFormatterRegistry.register` and the inline-widget factory
+  registration raise `ValueError` when a different registrant is given for a
+  type that already has one, instead of replacing it. Registering the same
+  one again does nothing.
+
 ## 0.1.2
 
 Requires ObjectState 3 (`objectstate>=3.0,<4`).
diff --git a/pyproject.toml b/pyproject.toml
index 73b59e4..1bb1af6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,12 +25,12 @@ keywords = ["forms", "reactive", "dataclass", "ui-bridge", "headless"]
 
 dependencies = [
     "docutils>=0.20",
-    "metaclass-registry>=0.1.5",
-    "objectstate>=3.0,<4",
+    "metaclass-registry>=0.4.0",
+    "objectstate>=3.0.1,<4",
     "psutil>=5.9",
     "python-introspect>=0.2.7,<0.3",
     "pyzmq>=22.0",
-    "zmqruntime>=0.6,<0.7",
+    "zmqruntime>=0.6.4,<0.7",
 ]
 
 [project.optional-dependencies]
diff --git a/requirements-ci.txt b/requirements-ci.txt
index 14a296b..4dcdd05 100644
--- a/requirements-ci.txt
+++ b/requirements-ci.txt
@@ -1,2 +1,2 @@
 # Source candidates needed to validate this checkout before coordinated publication.
-# Empty: every first-party dependency is released (objectstate 3.0.0).
+# Empty: every first-party dependency is released (objectstate 3.0.1, zmqruntime 0.6.4, metaclass-registry 0.4.0).
diff --git a/src/formbridge/__init__.py b/src/formbridge/__init__.py
index 088e276..456e797 100644
--- a/src/formbridge/__init__.py
+++ b/src/formbridge/__init__.py
@@ -4,4 +4,4 @@
 nothing and loads no GUI toolkit.
 """
 
-__version__ = "0.1.2"
+__version__ = "0.1.3"