fix up tests

Author: nicolaskruchten

Diff for: packages/python/plotly/plotly/express/_core.py

@@ -17,6 +17,7 @@
 )
 
 NO_COLOR = "px_no_color_constant"
+trendline_functions = dict(lowess=lowess, ma=ma, ewma=ewma, ols=ols)
 
 # Declare all supported attributes, across all plot types
 direct_attrables = (
@@ -286,10 +287,8 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
                 if trace_spec.constructor == go.Histogram:
                     mapping_labels["count"] = "%{x}"
             elif attr_name == "trendline":
-                trendline_functions = dict(lowess=lowess, ma=ma, ewma=ewma, ols=ols)
                 if (
-                    attr_value in trendline_functions
-                    and args["x"]
+                    args["x"]
                     and args["y"]
                     and len(trace_data[[args["x"], args["y"]]].dropna()) > 1
                 ):
@@ -1760,6 +1759,13 @@ def infer_config(args, constructor, trace_patch, layout_patch):
     ):
         args["facet_col_wrap"] = 0
 
+    if "trendline" in args and args["trendline"] is not None:
+        if args["trendline"] not in trendline_functions:
+            raise ValueError(
+                "Value '%s' for `trendline` must be one of %s"
+                % (args["trendline"], trendline_functions.keys())
+            )
+
     if "trendline_options" in args and args["trendline_options"] is None:
         args["trendline_options"] = dict()
 

Diff for: packages/python/plotly/plotly/express/trendline_functions/__init__.py

@@ -10,9 +10,17 @@ def ols(options, x_raw, x, y, x_label, y_label, non_missing):
     log_y = options.get("log_y", False)
 
     if log_y:
+        if np.any(y == 0):
+            raise ValueError(
+                "Can't do OLS trendline with `log_y=True` when `y` contains zeros."
+            )
         y = np.log(y)
         y_label = "log(%s)" % y_label
     if log_x:
+        if np.any(x == 0):
+            raise ValueError(
+                "Can't do OLS trendline with `log_x=True` when `x` contains zeros."
+            )
         x = np.log(x)
         x_label = "log(%s)" % x_label
     if add_constant:

Diff for: packages/python/plotly/plotly/tests/test_core/test_px/test_trendline.py

@@ -99,6 +99,7 @@ def test_trendline_enough_values(mode, options):
     "mode,options",
     [
         ("ols", None),
+        ("ols", dict(add_constant=False, log_x=True, log_y=True)),
         ("lowess", None),
         ("lowess", dict(frac=0.3)),
         ("ma", dict(window=2)),
@@ -124,7 +125,8 @@ def test_trendline_nan_values(mode, options):
 
 def test_ols_trendline_slopes():
     fig = px.scatter(x=[0, 1], y=[0, 1], trendline="ols")
-    assert "y = 1 * x + 0<br>" in fig.data[1].hovertemplate
+    # should be "y = 1 * x + 0" but sometimes is some tiny number instead
+    assert "y = 1 * x + " in fig.data[1].hovertemplate
     results = px.get_trendline_results(fig)
     params = results["px_fit_results"].iloc[0].params
     assert np.all(np.isclose(params, [0, 1]))