WIP: Adds dataExplorer.useLanguagePackFormatOptions setting, to format the Data Explorer using R or Python options

extensions/positron-python/python_files/posit/positron/data_explorer.py

@@ -607,6 +607,32 @@ def _compute_profiles(
                 raise NotImplementedError(profile_type)
         return ColumnProfileResult(**results)
 
+    def _get_format_options(self) -> FormatOptions | None:
+        """
+        Get format options based on current Python/NumPy display settings.
+        Returns None if using default formatting.
+
+        Subclasses can override this to provide backend-specific format options.
+        For example, to respect Python display settings:
+
+        import pandas as pd
+        precision = pd.get_option('display.precision')  # Default: 6
+
+        # Calculate max_integral_digits based on threshold for scientific notation
+        # Similar to R's scipen option
+        max_integral = 7  # Default threshold
+
+        return FormatOptions(
+            large_num_digits=precision,
+            small_num_digits=precision,
+            max_integral_digits=max_integral,
+            max_value_length=1000,
+            thousands_sep=None  # or ',' if desired
+        )
+        """
+        # For now, return None to use frontend defaults
+        return None
+
     def get_state(self, _unused):
         self._recompute_if_needed()
 
@@ -635,6 +661,7 @@ def get_state(self, _unused):
             row_filters=self.state.row_filters,
             sort_keys=self.state.sort_keys,
             supported_features=self.FEATURES,
+            format_options=self._get_format_options(),
         )
 
     def _recompute(self):

extensions/positron-python/python_files/posit/positron/data_explorer_comm.py

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2024-2025 Posit Software, PBC. All rights reserved.
+# Copyright (C) 2024-2026 Posit Software, PBC. All rights reserved.
 # Licensed under the Elastic License 2.0. See LICENSE.txt for license information.
 #
 
@@ -362,6 +362,11 @@ class BackendState(BaseModel):
         description="Optional experimental parameter to provide an explanation when connected=false. This parameter may change.",
     )
 
+    format_options: Optional[FormatOptions] = Field(
+        default=None,
+        description="Optional formatting options provided by the backend for displaying data values",
+    )
+
 
 class ColumnSchema(BaseModel):
     """

positron/comms/data_explorer-backend-openrpc.json

@@ -509,6 +509,10 @@
 						"error_message": {
 							"type": "string",
 							"description": "Optional experimental parameter to provide an explanation when connected=false. This parameter may change."
+						},
+						"format_options": {
+							"description": "Optional formatting options provided by the backend for displaying data values",
+							"$ref": "#/components/schemas/format_options"
 						}
 					}
 				}

positron/comms/data_explorer.md

@@ -6,6 +6,23 @@
 
 ## Backend Methods
 
+### get_state
+
+The `get_state` method returns the current backend state including table metadata and optional formatting options.
+
+#### Format Options
+
+The backend can optionally provide `format_options` in the state to control how numeric values are displayed. This allows backends to respect language-specific settings (e.g., R's `scipen` option).
+
+Format options include:
+* `large_num_digits`: Fixed number of decimal places for numbers over 1 or in scientific notation
+* `small_num_digits`: Fixed number of decimal places for small numbers and threshold for scientific notation
+* `max_integral_digits`: Maximum integral digits before switching to scientific notation
+* `max_value_length`: Maximum formatted value length for truncation
+* `thousands_sep`: Optional thousands separator character
+
+If format_options is not provided, the frontend will use sensible defaults.
+
 ### get_data_values
 
 Non-special values are returned formatted as strings.