BUG: Get eval results from metadata

myst_nb/core/execute/__init__.py

@@ -3,7 +3,12 @@
 from pathlib import Path, PurePosixPath
 from typing import TYPE_CHECKING
 
-from .base import ExecutionError, ExecutionResult, NotebookClientBase  # noqa: F401
+from .base import (
+    ExecutionError,  # noqa: F401
+    ExecutionResult,  # noqa: F401
+    NotebookClientBase,
+    NotebookClientReadOnly,
+)
 from .cache import NotebookClientCache
 from .direct import NotebookClientDirect
 from .inline import NotebookClientInline
@@ -48,15 +53,15 @@ def create_client(
         for pattern in nb_config.execution_excludepatterns:
             if posix_path.match(pattern):
                 logger.info(f"Excluded from execution by pattern: {pattern!r}")
-                return NotebookClientBase(notebook, path, nb_config, logger)
+                return NotebookClientReadOnly(notebook, path, nb_config, logger)
 
     # 'auto' mode only executes the notebook if it is missing at least one output
     missing_outputs = (
         len(cell.outputs) == 0 for cell in notebook.cells if cell["cell_type"] == "code"
     )
     if nb_config.execution_mode == "auto" and not any(missing_outputs):
         logger.info("Skipped execution in 'auto' mode (all outputs present)")
-        return NotebookClientBase(notebook, path, nb_config, logger)
+        return NotebookClientReadOnly(notebook, path, nb_config, logger)
 
     if nb_config.execution_mode in ("auto", "force"):
         return NotebookClientDirect(notebook, path, nb_config, logger)
@@ -67,4 +72,4 @@ def create_client(
     if nb_config.execution_mode == "inline":
         return NotebookClientInline(notebook, path, nb_config, logger)
 
-    return NotebookClientBase(notebook, path, nb_config, logger)
+    return NotebookClientReadOnly(notebook, path, nb_config, logger)

myst_nb/core/execute/base.py

@@ -42,7 +42,7 @@ class EvalNameError(Exception):
 
 
 class NotebookClientBase:
-    """A base client for interacting with Jupyter notebooks.
+    """A client base class for interacting with Jupyter notebooks.
 
     This class is intended to be used as a context manager,
     and should only be entered once.
@@ -181,7 +181,30 @@ def eval_variable(
         :raises NotImplementedError: if the execution mode does not support this feature
         :raises EvalNameError: if the variable name is invalid
         """
+        raise NotImplementedError
+
+
+class NotebookClientReadOnly(NotebookClientBase):
+    """A notebook client that does not execute the notebook."""
+
+    def eval_variable(
+        self, name: str, current_cell: SyntaxTreeNode
+    ) -> list[NotebookNode]:
+        """Retrieve the value of a variable from the current cell metadata if possible.
+
+        :param name: the name of the variable
+        :returns: code cell outputs
+        :raises RetrievalError: if the cell metadata does not contain the eval result
+        :raises EvalNameError: if the variable name is invalid
+        """
         for ux in current_cell.meta.get("metadata", {}).get("user_expressions", []):
             if ux["expression"] == name:
                 return from_dict([ux["result"]])
-        raise NotImplementedError
+
+        from myst_nb.core.variables import RetrievalError
+
+        msg = (
+            f"Cell {current_cell.meta.get('index', '')} does "
+            f"not contain execution result for variable {name!r}"
+        )
+        raise RetrievalError(msg)

myst_nb/ext/eval/__init__.py

@@ -42,6 +42,8 @@ def retrieve_eval_data(document: nodes.document, key: str) -> list[VariableOutpu
         outputs = element.renderer.nb_client.eval_variable(
             key, element.renderer.current_cell
         )
+    except RetrievalError:
+        raise
     except NotImplementedError:
         raise RetrievalError("This document does not have a running kernel")
     except EvalNameError:

tests/notebooks/with_eval.md

@@ -2,8 +2,6 @@
 file_format: mystnb
 kernelspec:
   name: python3
-mystnb:
-    execution_mode: 'inline'
 ---
 
 # Inline evaluation

tests/test_eval.py

@@ -25,3 +25,17 @@ def test_no_build(sphinx_run, clean_doctree, file_regression):
     assert sphinx_run.warnings() == ""
     doctree = clean_doctree(sphinx_run.get_resolved_doctree("with_eval_executed"))
     file_regression.check(doctree.pformat(), encoding="utf-8")
+
+
+@pytest.mark.sphinx_params("with_eval.md", conf={"nb_execution_mode": "off"})
+def test_no_build_error(sphinx_run):
+    """Test that lack of execution results errors."""
+    sphinx_run.build()
+    assert (
+        "Cell 2 does not contain execution result for variable 'a'"
+        in sphinx_run.warnings()
+    )
+    assert (
+        "Cell 4 does not contain execution result for variable 'img'"
+        in sphinx_run.warnings()
+    )