Fix: Empty string as template in CustomPlot.init (#841)

* Fix: Empty string as template in CustomPlot.init

Fixed dvc issue #10482 at iterative/dvc#10482

* Fix None template in Custom Plot constructor

* Update src/dvclive/plots/custom.py

Co-authored-by: skshetry <18718008+skshetry@users.noreply.github.com>

* Remove unnecesary tests in plots/test_custom.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: skshetry <18718008+skshetry@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/dvclive/plots/custom.py

@@ -23,6 +23,9 @@ def __init__(
     ) -> None:
         super().__init__(name, output_folder)
         self.name = self.name.replace(".json", "")
+        if not template:
+            template = None
+
         config = {
             "template": template,
             "x": x,

tests/plots/test_custom.py

@@ -56,3 +56,30 @@ def test_log_custom_plot_multi_y(tmp_dir):
         "x_label": "x_label",
         "y_label": "y_label",
     }
+
+
+def test_log_custom_plot_with_template_as_empty_string(tmp_dir):
+    live = Live()
+    out = tmp_dir / live.plots_dir / CustomPlot.subfolder
+
+    datapoints = [{"x": 1, "y": 2}, {"x": 3, "y": 4}]
+    live.log_plot(
+        "custom_linear",
+        datapoints,
+        x="x",
+        y="y",
+        template="",
+        title="custom_title",
+        x_label="x_label",
+        y_label="y_label",
+    )
+
+    assert json.loads((out / "custom_linear.json").read_text()) == datapoints
+    # 'template' should not be in plot_config. Default template will be assigned later.
+    assert live._plots["custom_linear"].plot_config == {
+        "title": "custom_title",
+        "x": "x",
+        "y": "y",
+        "x_label": "x_label",
+        "y_label": "y_label",
+    }