fix: make math_eq_editor preview state-driven

src/pdealchemy/notebook_utils.py

@@ -96,16 +96,18 @@ def math_eq_editor(
         source_text = _read_equation_source(source_path)
     except OSError as exc:
         return mo.md(f"**Error loading equation file** `{content}`: {exc}")
+    get_source_text, set_source_text = mo.state(source_text)
 
     source_editor = mo.ui.code_editor(
         value=source_text,
         language="markdown",
         label=f"Equation source: {content}",
+        on_change=set_source_text,
     )
 
     def _save_source(_value: object) -> str:
         try:
-            source_path.write_text(str(source_editor.value), encoding="utf-8")
+            source_path.write_text(str(get_source_text()), encoding="utf-8")
         except OSError as exc:
             return f"Save failed: {exc}"
         return f"Saved `{content}`."
@@ -116,7 +118,7 @@ def _save_source(_value: object) -> str:
         kind="success",
     )
     preview = _render_equation_block(
-        latex=_extract_first_latex_block(str(source_editor.value)),
+        latex=_extract_first_latex_block(str(get_source_text())),
         name=name,
         mo=mo,
     )

tests/notebook/test_notebook_utils.py

@@ -18,8 +18,18 @@ def _fake_marimo_module() -> SimpleNamespace:
 
 
 class _FakeCodeEditor:
-    def __init__(self, value: str) -> None:
-        self.value = value
+    def __init__(self, value: str, on_change: Any | None = None) -> None:
+        self._value = value
+        self._on_change = on_change
+
+    @property
+    def value(self) -> str:
+        return self._value
+
+    def set_value(self, value: str) -> None:
+        self._value = value
+        if self._on_change is not None:
+            self._on_change(value)
 
 
 class _FakeButton:
@@ -43,16 +53,23 @@ def click(self) -> Any:
         return self._on_click(None)
 
 
+class _NoValueReadEditor(_FakeCodeEditor):
+    @property
+    def value(self) -> str:
+        raise RuntimeError("Accessing editor.value in creating cell is not allowed")
+
+
 class _FakeUi:
     def code_editor(
         self,
         value: str,
         *,
         language: str,
         label: str,
+        on_change: Any | None = None,
     ) -> _FakeCodeEditor:
         _ = (language, label)
-        return _FakeCodeEditor(value)
+        return _FakeCodeEditor(value, on_change=on_change)
 
     def button(
         self,
@@ -76,8 +93,31 @@ def md(text: str) -> tuple[str, str]:
     def vstack(blocks: list[object]) -> tuple[str, list[object]]:
         return ("vstack", blocks)
 
+    @staticmethod
+    def state(value: str) -> tuple[Any, Any]:
+        payload: dict[str, str] = {"value": value}
+
+        def _get() -> str:
+            return payload["value"]
+
+        def _set(new_value: str) -> None:
+            payload["value"] = new_value
+
+        return _get, _set
+
 
 class _NoValueReadUi(_FakeUi):
+    def code_editor(
+        self,
+        value: str,
+        *,
+        language: str,
+        label: str,
+        on_change: Any | None = None,
+    ) -> _NoValueReadEditor:
+        _ = (language, label)
+        return _NoValueReadEditor(value, on_change=on_change)
+
     def button(
         self,
         *,
@@ -100,6 +140,18 @@ def md(text: str) -> tuple[str, str]:
     def vstack(blocks: list[object]) -> tuple[str, list[object]]:
         return ("vstack", blocks)
 
+    @staticmethod
+    def state(value: str) -> tuple[Any, Any]:
+        payload: dict[str, str] = {"value": value}
+
+        def _get() -> str:
+            return payload["value"]
+
+        def _set(new_value: str) -> None:
+            payload["value"] = new_value
+
+        return _get, _set
+
 
 def test_math_eq_renders_raw_latex(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(notebook_utils, "_load_marimo_module", _fake_marimo_module)
@@ -242,7 +294,7 @@ def test_math_eq_editor_persists_edited_source(
     rendered = notebook_utils.math_eq_editor(str(equation_file))
     editor = next(block for block in rendered[1] if isinstance(block, _FakeCodeEditor))
     button = next(block for block in rendered[1] if isinstance(block, _FakeButton))
-    editor.value = "\\[\nS-K\n\\]"
+    editor.set_value("\\[\nS-K\n\\]")
 
     button.click()