fix: depth contour style_function reads from feature properties (APR-169)

app/components/dnr_map.py

@@ -99,17 +99,14 @@ def add_depth_contours(
 
     fg = folium.FeatureGroup(name="Depth Contours", show=show)
 
-    for feature in geojson_data.get("features", []):
-        depth = feature.get("properties", {}).get("depth_ft", 0)
-        color = _depth_to_color(depth)
-        style = {**_CONTOUR_STYLE_BASE, "color": color}
-        tooltip = f"{depth:.0f} ft"
-
-        folium.GeoJson(
-            feature,
-            style_function=lambda x, s=style: s,
-            tooltip=tooltip,
-        ).add_to(fg)
+    folium.GeoJson(
+        geojson_data,
+        style_function=lambda x: {
+            **_CONTOUR_STYLE_BASE,
+            "color": _depth_to_color(x["properties"].get("depth_ft", 0)),
+        },
+        tooltip=folium.GeoJsonTooltip(fields=["depth_ft"], aliases=["Depth (ft):"]),
+    ).add_to(fg)
 
     fg.add_to(m)
     return fg
@@ -148,7 +145,7 @@ def add_species_zone_overlay(
 
     folium.GeoJson(
         collection,
-        style_function=lambda x, s=style: s,
+        style_function=lambda x: style,
         tooltip=f"{species_name}: {depth_range[0]:.0f}-{depth_range[1]:.0f} ft preferred",
     ).add_to(fg)
 

tests/test_dnr_map_bathymetry.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import json
+import re
 from pathlib import Path
 from typing import Any, Dict
 
@@ -10,6 +11,7 @@
 try:
     import folium
     from components.dnr_map import (
+        _depth_to_color,
         add_depth_contours,
         add_species_zone_overlay,
         build_lake_map,
@@ -70,6 +72,18 @@ def test_returns_none_when_no_data(self, tmp_path):
         fg = add_depth_contours(m, "Nonexistent Lake", bathymetry_dir=tmp_path)
         assert fg is None
 
+    def test_style_function_reads_depth_from_properties(self, sample_contour_geojson):
+        """style_function must extract depth_ft from feature properties, producing distinct
+        colors for different depths — not a static style that ignores feature properties."""
+        m = folium.Map(location=[45.3, -94.1], zoom_start=10)
+        add_depth_contours(m, "Clearwater", bathymetry_dir=sample_contour_geojson)
+        html = m._repr_html_()
+        color_10ft = _depth_to_color(10.0)
+        color_25ft = _depth_to_color(25.0)
+        assert color_10ft != color_25ft, "test requires two distinct depth colors"
+        assert color_10ft in html, f"expected color for 10 ft ({color_10ft}) not found in rendered HTML"
+        assert color_25ft in html, f"expected color for 25 ft ({color_25ft}) not found in rendered HTML"
+
 
 class TestAddSpeciesZoneOverlay:
     def test_adds_zone_for_matching_depths(self, sample_contour_geojson):