gui: Fix possibly indexing None in psmap.utils.convertRGB (#4875)

Fully type check and annotate convertRGB() and the grass.script.core.parse_color() functions

gui/wxpython/psmap/utils.py

@@ -19,6 +19,7 @@
 from __future__ import annotations
 
 from math import ceil, cos, floor, fmod, radians, sin
+from typing import overload
 
 import wx
 from core.gcmd import GError, RunCommand
@@ -148,7 +149,17 @@ def convert(self, value, fromUnit=None, toUnit=None):
         return float(value) / self._units[fromUnit]["val"] * self._units[toUnit]["val"]
 
 
-def convertRGB(rgb):
+@overload
+def convertRGB(rgb: wx.Colour) -> str:
+    pass
+
+
+@overload
+def convertRGB(rgb: str) -> wx.Colour | None:
+    pass
+
+
+def convertRGB(rgb: wx.Colour | str) -> str | wx.Colour | None:
     """Converts wx.Colour(r,g,b,a) to string 'r:g:b' or named color,
     or named color/r:g:b string to wx.Colour, depending on input"""
     # transform a wx.Colour tuple into an r:g:b string
@@ -162,12 +173,10 @@ def convertRGB(rgb):
                 return name
         return str(rgb.Red()) + ":" + str(rgb.Green()) + ":" + str(rgb.Blue())
     # transform a GRASS named color or an r:g:b string into a wx.Colour tuple
-    color = (
-        int(gs.parse_color(rgb)[0] * 255),
-        int(gs.parse_color(rgb)[1] * 255),
-        int(gs.parse_color(rgb)[2] * 255),
-    )
-    color = wx.Colour(*color)
+    parsed_color = gs.parse_color(rgb)
+    if parsed_color is None:
+        return None
+    color = wx.Colour(*tuple(int(x * 255) for x in parsed_color))
     if color.IsOk():
         return color
     return None

python/grass/script/core.py

@@ -1575,7 +1575,7 @@ def list_grouped(
 
 # color parsing
 
-named_colors = {
+named_colors: dict[str, tuple[float, float, float]] = {
     "white": (1.00, 1.00, 1.00),
     "black": (0.00, 0.00, 0.00),
     "red": (1.00, 0.00, 0.00),
@@ -1595,7 +1595,9 @@ def list_grouped(
 }
 
 
-def parse_color(val, dflt=None):
+def parse_color(
+    val: str, dflt: tuple[float, float, float] | None = None
+) -> tuple[float, float, float] | None:
     """Parses the string "val" as a GRASS colour, which can be either one of
     the named colours or an R:G:B tuple e.g. 255:255:255. Returns an
     (r,g,b) triple whose components are floating point values between 0
@@ -1614,9 +1616,9 @@ def parse_color(val, dflt=None):
     if val in named_colors:
         return named_colors[val]
 
-    vals = val.split(":")
+    vals: list[str] = val.split(":")
     if len(vals) == 3:
-        return tuple(float(v) / 255 for v in vals)
+        return (float(vals[0]) / 255, float(vals[1]) / 255, float(vals[2]) / 255)
 
     return dflt