fix infinite loop in stringify and add test case

Also bump to 0.6.2

3 files changed, 6 insertions, 4 deletions

diff --git a/setup.py b/setup.py
index bd5ff09..c9b7d20 100644
--- a/setup.py
+++ b/setup.py
@@ -25,7 +25,7 @@ with open('README', 'r') as f:
 
 setup(
         name='taler-util',
-        version='0.6.1',
+        version='0.6.2',
         license='LGPL3+',
         platforms='any',
         author='Taler Systems SA',
diff --git a/taler/util/amount.py b/taler/util/amount.py
index c768f30..3891326 100644
--- a/taler/util/amount.py
+++ b/taler/util/amount.py
@@ -232,7 +232,7 @@ class Amount:
     # Convert the amount to a string.
     #
     # @param self this object.
-    # @param ndigits how many digits we want for the fractional part.
+    # @param ndigits minimum number of digits to display in the fractional part
     # @param pretty if True, put the currency in the last position and
     #        omit the colon.
     def stringify(self, ndigits=0, pretty=False) -> str:
@@ -240,10 +240,11 @@ class Amount:
         if self.fraction != 0:
             s += "."
             frac = self.fraction
-            while frac != 0 or ndigits != 0:
+            while frac > 0 or (ndigits is not None and ndigits > 0):
                 s += str(int(frac / (Amount._fraction() / 10)))
                 frac = (frac * 10) % (Amount._fraction())
-                ndigits -= 1
+                if ndigits > 0:
+                    ndigits -= 1
         elif ndigits != 0:
             s += "." + ("0" * ndigits)
         if not pretty:
diff --git a/tests/test_amount.py b/tests/test_amount.py
index 67d9844..a4043b7 100755
--- a/tests/test_amount.py
+++ b/tests/test_amount.py
@@ -68,3 +68,4 @@ class TestAmount(TestCase):
         self.assertEqual(self.amount.stringify(3), 'TESTKUDOS:0.000')
         self.amount.add(Amount('TESTKUDOS', 2, 100))
         self.assertEqual(self.amount.stringify(6), 'TESTKUDOS:2.000001')
+        self.assertEqual(Amount("TESTKUDOS", value=5, fraction=9000000).stringify(), 'TESTKUDOS:5.09')