Fill template anchors inside custom template strings (#145)

* Fill template anchors inserted into custom template strings

* Appease mypy

src/dvc_render/vega.py

@@ -117,22 +117,23 @@ def generate_markdown(self, report_path=None) -> str:
             data[x] = list(map(float, data[x]))
             data[y] = list(map(float, data[y]))
 
-            plt.title(self.properties.get("title", Path(self.name).stem))
-            plt.xlabel(self.properties.get("x_label", x))
-            plt.ylabel(self.properties.get("y_label", y))
-            plt.plot(x, y, data=data)
-            plt.tight_layout()
-            plt.savefig(output_file)
-            plt.close()
-
-            if report_path:
-                return f"\n![{self.name}]({output_file.relative_to(report_folder)})"
-
-            base64_str = base64.b64encode(
-                output_file.getvalue()  # type: ignore
-            ).decode()
-            src = f"data:image/png;base64,{base64_str}"
-
-            return f"\n![{self.name}]({src})"
+            if x is not None and y is not None:
+                plt.title(self.properties.get("title", Path(self.name).stem))
+                plt.xlabel(self.properties.get("x_label", x))
+                plt.ylabel(self.properties.get("y_label", y))
+                plt.plot(x, y, data=data)
+                plt.tight_layout()
+                plt.savefig(output_file)
+                plt.close()
+
+                if report_path:
+                    return f"\n![{self.name}]({output_file.relative_to(report_folder)})"
+
+                base64_str = base64.b64encode(
+                    output_file.getvalue()  # type: ignore
+                ).decode()
+                src = f"data:image/png;base64,{base64_str}"
+
+                return f"\n![{self.name}]({src})"
 
         return ""

src/dvc_render/vega_templates.py

@@ -43,6 +43,8 @@ def dict_replace_value(d: dict, name: str, value: Any) -> dict:
             if v == name:
                 x[k] = value
                 continue
+            if name in v and isinstance(value, str):
+                v = v.replace(name, value)
         x[k] = v
     return x
 

tests/test_vega.py

@@ -229,3 +229,41 @@ def test_escape_special_characters():
     assert filled["encoding"]["x"]["title"] == "foo.bar[0]"
     assert filled["encoding"]["y"]["field"] == "foo\\.bar\\[1\\]"
     assert filled["encoding"]["y"]["title"] == "foo.bar[1]"
+
+
+def test_fill_anchor_in_string(tmp_dir):
+    y = "lab"
+    x = "SR"
+    tmp_dir.gen(
+        "custom.json",
+        json.dumps(
+            {
+                "data": {"values": Template.anchor("data")},
+                "transform": [
+                    {"joinaggregate": [{"op": "mean", "field": "lab", "as": "mean_y"}]},
+                    {
+                        "calculate": "pow("
+                        + "datum.<DVC_METRIC_Y> - datum.<DVC_METRIC_X>,2"
+                        + ")",
+                        "as": "SR",
+                    },
+                    {"joinaggregate": [{"op": "sum", "field": "SR", "as": "SSR"}]},
+                ],
+                "encoding": {
+                    "x": {"field": Template.anchor("x")},
+                    "y": {"field": Template.anchor("y")},
+                },
+            },
+        ),
+    )
+    datapoints = [
+        {x: "B", y: "A"},
+        {x: "A", y: "A"},
+    ]
+    props = {"template": "custom.json", "x": x, "y": y}
+
+    renderer = VegaRenderer(datapoints, "foo", **props)
+    filled = renderer.get_filled_template(as_string=False)
+    assert filled["transform"][1]["calculate"] == "pow(datum.lab - datum.SR,2)"
+    assert filled["encoding"]["x"]["field"] == x
+    assert filled["encoding"]["y"]["field"] == y