feat(mcp): add horizontal bar chart orientation support to generate_chart (#38390)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

superset/mcp_service/chart/chart_utils.py

@@ -468,6 +468,17 @@ def add_legend_config(form_data: Dict[str, Any], config: XYChartConfig) -> None:
             form_data["legend_orientation"] = config.legend.position
 
 
+def add_orientation_config(form_data: Dict[str, Any], config: XYChartConfig) -> None:
+    """Add orientation configuration to form_data for bar charts.
+
+    Only applies when kind='bar' and an explicit orientation is set.
+    When orientation is None (the default), Superset uses its own default
+    (vertical bars).
+    """
+    if config.kind == "bar" and config.orientation:
+        form_data["orientation"] = config.orientation
+
+
 def configure_temporal_handling(
     form_data: Dict[str, Any],
     x_is_temporal: bool,
@@ -576,6 +587,7 @@ def map_xy_config(
     # Add configurations
     add_axis_config(form_data, config)
     add_legend_config(form_data, config)
+    add_orientation_config(form_data, config)
 
     return form_data
 

superset/mcp_service/chart/resources/chart_configs.py

@@ -129,6 +129,29 @@ def get_chart_configs_resource() -> str:
             },
             "use_cases": ["Correlation analysis", "Outlier detection"],
         },
+        "horizontal_bar": {
+            "description": "Horizontal bar chart for categories with long names",
+            "config": {
+                "chart_type": "xy",
+                "kind": "bar",
+                "orientation": "horizontal",
+                "x": {"name": "department", "label": "Department"},
+                "y": [
+                    {
+                        "name": "headcount",
+                        "aggregate": "SUM",
+                        "label": "Headcount",
+                    }
+                ],
+                "y_axis": {"title": "Department"},
+                "x_axis": {"title": "Number of Employees"},
+            },
+            "use_cases": [
+                "Long category labels",
+                "Rankings and leaderboards",
+                "Survey results",
+            ],
+        },
         "stacked_area": {
             "description": "Stacked area chart for volume composition over time",
             "config": {
@@ -215,6 +238,7 @@ def get_chart_configs_resource() -> str:
             "Use group_by to split data into series for comparison",
             "Use stacked=true for bar/area charts showing composition",
             "Configure axis format for readability ($,.0f for currency, .2% for pct)",
+            "Use orientation='horizontal' for bar charts with long category names",
         ],
         "table_charts": [
             "Include only essential columns to avoid clutter",

superset/mcp_service/chart/schemas.py

@@ -749,6 +749,14 @@ class XYChartConfig(BaseModel):
             "If not specified, Superset will use its default behavior."
         ),
     )
+    orientation: Literal["vertical", "horizontal"] | None = Field(
+        None,
+        description=(
+            "Bar chart orientation. Only applies when kind='bar'. "
+            "'vertical' (default): bars extend upward. "
+            "'horizontal': bars extend rightward, useful for long category names."
+        ),
+    )
     stacked: bool = Field(
         False,
         description="Stack bars/areas on top of each other instead of side-by-side",

tests/unit_tests/mcp_service/chart/test_chart_schemas.py

@@ -243,6 +243,61 @@ class TestXYChartConfig:
         assert config.group_by is not None
         assert config.group_by.name == "year"
 
+    def test_orientation_horizontal_accepted(self) -> None:
+        """Test that orientation='horizontal' is accepted for bar charts."""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="department"),
+            y=[ColumnRef(name="headcount", aggregate="SUM")],
+            kind="bar",
+            orientation="horizontal",
+        )
+        assert config.orientation == "horizontal"
+
+    def test_orientation_vertical_accepted(self) -> None:
+        """Test that orientation='vertical' is accepted for bar charts."""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="category"),
+            y=[ColumnRef(name="sales", aggregate="SUM")],
+            kind="bar",
+            orientation="vertical",
+        )
+        assert config.orientation == "vertical"
+
+    def test_orientation_none_by_default(self) -> None:
+        """Test that orientation defaults to None when not specified."""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="category"),
+            y=[ColumnRef(name="sales", aggregate="SUM")],
+            kind="bar",
+        )
+        assert config.orientation is None
+
+    def test_orientation_invalid_value_rejected(self) -> None:
+        """Test that invalid orientation values are rejected."""
+        with pytest.raises(ValidationError):
+            XYChartConfig(
+                chart_type="xy",
+                x=ColumnRef(name="category"),
+                y=[ColumnRef(name="sales", aggregate="SUM")],
+                kind="bar",
+                orientation="diagonal",
+            )
+
+    def test_orientation_with_non_bar_chart(self) -> None:
+        """Test that orientation field is accepted on non-bar charts at schema level."""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="date"),
+            y=[ColumnRef(name="revenue", aggregate="SUM")],
+            kind="line",
+            orientation="horizontal",
+        )
+        # Schema allows it; the chart_utils layer decides whether to apply it
+        assert config.orientation == "horizontal"
+
 
 class TestTableChartConfigExtraFields:
     """Test TableChartConfig rejects unknown fields."""

tests/unit_tests/mcp_service/chart/test_chart_utils.py

@@ -460,6 +460,84 @@ class TestMapXYConfig:
         assert result["groupby"] == ["category"]
         assert result["x_axis"] == "order_date"
 
+    def test_map_xy_config_bar_horizontal_orientation(self) -> None:
+        """Test XY config mapping for horizontal bar chart"""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="department"),
+            y=[ColumnRef(name="headcount", aggregate="SUM")],
+            kind="bar",
+            orientation="horizontal",
+        )
+
+        result = map_xy_config(config)
+
+        assert result["viz_type"] == "echarts_timeseries_bar"
+        assert result["orientation"] == "horizontal"
+
+    def test_map_xy_config_bar_vertical_orientation(self) -> None:
+        """Test XY config mapping for vertical bar chart (explicit)"""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="category"),
+            y=[ColumnRef(name="sales", aggregate="SUM")],
+            kind="bar",
+            orientation="vertical",
+        )
+
+        result = map_xy_config(config)
+
+        assert result["viz_type"] == "echarts_timeseries_bar"
+        assert result["orientation"] == "vertical"
+
+    def test_map_xy_config_bar_no_orientation(self) -> None:
+        """Test XY config mapping for bar chart without orientation."""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="category"),
+            y=[ColumnRef(name="sales", aggregate="SUM")],
+            kind="bar",
+        )
+
+        result = map_xy_config(config)
+
+        assert result["viz_type"] == "echarts_timeseries_bar"
+        assert "orientation" not in result
+
+    def test_map_xy_config_line_orientation_ignored(self) -> None:
+        """Test that orientation is ignored for non-bar chart types"""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="date"),
+            y=[ColumnRef(name="revenue", aggregate="SUM")],
+            kind="line",
+            orientation="horizontal",
+        )
+
+        result = map_xy_config(config)
+
+        assert result["viz_type"] == "echarts_timeseries_line"
+        assert "orientation" not in result
+
+    def test_map_xy_config_bar_horizontal_with_stacked(self) -> None:
+        """Test horizontal bar chart with stacked option"""
+        config = XYChartConfig(
+            chart_type="xy",
+            x=ColumnRef(name="department"),
+            y=[ColumnRef(name="headcount", aggregate="SUM")],
+            kind="bar",
+            orientation="horizontal",
+            stacked=True,
+            group_by=ColumnRef(name="level"),
+        )
+
+        result = map_xy_config(config)
+
+        assert result["viz_type"] == "echarts_timeseries_bar"
+        assert result["orientation"] == "horizontal"
+        assert result["stack"] == "Stack"
+        assert result["groupby"] == ["level"]
+
 
 class TestMapConfigToFormData:
     """Test map_config_to_form_data function"""