fix: add simple rendering logic for currency values and errors

src/wuttjamaican/app.py

@@ -34,7 +34,7 @@ import humanize
 
 from wuttjamaican.util import (load_entry_points, load_object,
                                make_title, make_uuid, make_true_uuid,
-                               progress_loop, resource_path)
+                               progress_loop, resource_path, simple_error)
 
 
 class AppHandler:
@@ -676,6 +676,28 @@ class AppHandler:
     # common value renderers
     ##############################
 
+    def render_currency(self, value, scale=2, **kwargs):
+        """
+        Return a human-friendly display string for the given currency
+        value, e.g. ``Decimal('4.20')`` becomes ``"$4.20"``.
+
+        :param value: Either a :class:`python:decimal.Decimal` or
+           :class:`python:float` value.
+
+        :param scale: Number of decimal digits to be displayed.
+
+        :returns: Display string for the value.
+        """
+        if value is None:
+            return ''
+
+        if value < 0:
+            fmt = f"(${{:0,.{scale}f}})"
+            return fmt.format(0 - value)
+
+        fmt = f"${{:0,.{scale}f}}"
+        return fmt.format(value)
+
     display_format_date = '%Y-%m-%d'
     """
     Format string to use when displaying :class:`python:datetime.date`
@@ -717,6 +739,16 @@ class AppHandler:
         if value is not None:
             return value.strftime(self.display_format_datetime)
 
+    def render_error(self, error):
+        """
+        Return a "human-friendly" display string for the error, e.g.
+        when showing it to the user.
+
+        By default, this is a convenience wrapper for
+        :func:`~wuttjamaican.util.simple_error()`.
+        """
+        return simple_error(error)
+
     def render_time_ago(self, value):
         """
         Return a human-friendly string, indicating how long ago

src/wuttjamaican/util.py

@@ -338,3 +338,22 @@ def resource_path(path):
             return str(path)
 
     return path
+
+
+def simple_error(error):
+    """
+    Return a "simple" string for the given error.  Result will look
+    like::
+
+       "ErrorClass: Description for the error"
+
+    However the logic checks to ensure the error has a descriptive
+    message first; if it doesn't the result will just be::
+
+       "ErrorClass"
+    """
+    cls = type(error).__name__
+    msg = str(error)
+    if msg:
+        return f"{cls}: {msg}"
+    return cls

tests/test_app.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8; -*-
 
 import datetime
+import decimal
 import os
 import shutil
 import sys
@@ -422,6 +423,31 @@ app_title = WuttaTest
         session = self.app.get_session(user)
         self.assertIs(session, mysession)
 
+    def test_render_currency(self):
+
+        # null
+        self.assertEqual(self.app.render_currency(None), '')
+
+        # basic decimal example
+        value = decimal.Decimal('42.00')
+        self.assertEqual(self.app.render_currency(value), '$42.00')
+
+        # basic float example
+        value = 42.00
+        self.assertEqual(self.app.render_currency(value), '$42.00')
+
+        # decimal places will be rounded
+        value = decimal.Decimal('42.12345')
+        self.assertEqual(self.app.render_currency(value), '$42.12')
+
+        # but we can declare the scale
+        value = decimal.Decimal('42.12345')
+        self.assertEqual(self.app.render_currency(value, scale=4), '$42.1234')
+
+        # negative numbers get parens
+        value = decimal.Decimal('-42.42')
+        self.assertEqual(self.app.render_currency(value), '($42.42)')
+
     def test_render_date(self):
         self.assertIsNone(self.app.render_date(None))
 
@@ -434,6 +460,22 @@ app_title = WuttaTest
         dt = datetime.datetime(2024, 12, 11, 8, 30, tzinfo=datetime.timezone.utc)
         self.assertEqual(self.app.render_datetime(dt), '2024-12-11 08:30+0000')
 
+    def test_simple_error(self):
+
+        # with description
+        try:
+            raise RuntimeError("just testin")
+        except Exception as error:
+            result = self.app.render_error(error)
+        self.assertEqual(result, "RuntimeError: just testin")
+
+        # without description
+        try:
+            raise RuntimeError
+        except Exception as error:
+            result = self.app.render_error(error)
+        self.assertEqual(result, "RuntimeError")
+
     def test_render_time_ago(self):
         with patch.object(mod, 'humanize') as humanize:
             humanize.naturaltime.return_value = 'now'

tests/test_util.py

@@ -317,3 +317,20 @@ class TestResourcePath(TestCase):
 
             # absolute path returned as-is
             self.assertEqual(mod.resource_path('/tmp/doesnotexist.txt'), '/tmp/doesnotexist.txt')
+
+
+class TestSimpleError(TestCase):
+
+    def test_with_description(self):
+        try:
+            raise RuntimeError("just testin")
+        except Exception as error:
+            result = mod.simple_error(error)
+        self.assertEqual(result, "RuntimeError: just testin")
+
+    def test_without_description(self):
+        try:
+            raise RuntimeError
+        except Exception as error:
+            result = mod.simple_error(error)
+        self.assertEqual(result, "RuntimeError")