Math: make `@icalc` fail early when result is too large

This avoids inconsistent errors between CPython 3.10.7 and older
versions; and the result would not be readable anyway.

Closes GH-1517.

plugins/Math/plugin.py

@@ -166,8 +166,8 @@ class Math(callbacks.Plugin):
         """
         try:
             self.log.info('evaluating %q from %s', text, msg.prefix)
-            x = safe_eval(text, allow_ints=True)
-            irc.reply(str(x))
+            result = safe_eval(text, allow_ints=True)
+            float(result)  # fail early if it is too large to be displayed
         except OverflowError:
             maxFloat = math.ldexp(0.9999999999999999, 1024)
             irc.error(_('The answer exceeded %s or so.') % maxFloat)
@@ -177,6 +177,17 @@ class Math(callbacks.Plugin):
             irc.error(_('%s is not a defined function.') % str(e).split()[1])
         except Exception as e:
             irc.error(utils.exnToString(e))
+        else:
+            try:
+                result_str = str(result)
+            except ValueError as e:
+                # Probably too large to be converted to string; go through
+                # floats instead.
+                # https://docs.python.org/3/library/stdtypes.html#int-max-str-digits
+                # (Depending on configuration, this may be dead code because it
+                # is caught by the float() check above.
+                result_str = str(float(result))
+            irc.reply(result_str)
     icalc = wrap(icalc, [('checkCapability', 'trusted'), 'text'])
 
     _rpnEnv = {

plugins/Math/test.py

@@ -112,7 +112,10 @@ class MathTestCase(PluginTestCase):
         self.assertNotError('calc (1600 * 1200) - 2*(1024*1280)')
         self.assertNotError('calc 3-2*4')
         self.assertNotError('calc (1600 * 1200)-2*(1024*1280)')
-        self.assertError('calc factorial(20000)')
+        self.assertResponse('calc factorial(20000)',
+            'Error: factorial argument too large')
+        self.assertResponse('calc factorial(20000) / factorial(19999)',
+            'Error: factorial argument too large')
 
     def testCalcNoNameError(self):
         self.assertRegexp('calc foobar(x)', 'foobar is not a defined function')
@@ -147,7 +150,10 @@ class MathTestCase(PluginTestCase):
         self.assertResponse('icalc 1^1', '0')
         self.assertResponse('icalc 10**24', '1' + '0'*24)
         self.assertRegexp('icalc 49/6', '8.16')
-        self.assertNotError('icalc factorial(20000)')
+        self.assertRegexp('icalc factorial(20000)',
+            'Error: The answer exceeded')
+        self.assertResponse('icalc factorial(20000) / factorial(19999)',
+            '20000.0')
 
     def testRpn(self):
         self.assertResponse('rpn 5 2 +', '7')