Raise ValueError for truncated path commands instead of a bare IndexError

svgpathtools/path.py

@@ -44,6 +44,10 @@
 COMMANDS = set('MmZzLlHhVvCcSsQqTtAa')
 UPPERCASE = set('MZLHVCSQTA')
 
+# Number of numeric parameters each command consumes per repetition.
+COMMAND_NUM_ARGS = {'M': 2, 'L': 2, 'H': 1, 'V': 1, 'C': 6,
+                    'S': 4, 'Q': 4, 'T': 2, 'A': 7, 'Z': 0}
+
 COMMAND_RE = re.compile(r"([MmZzLlHhVvCcSsQqTtAa])")
 FLOAT_RE = re.compile(r"[-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?")
 
@@ -3227,6 +3231,15 @@ def _parse_path(self, pathdef, current_pos=0j, tree_element=None):
                         pathdef, len(pathdef.split()) - len(elements)))
                 last_command = command  # Used by S and T
 
+            # A command must be followed by its full set of coordinates; a
+            # truncated path (e.g. "M 0 0 L") would otherwise pop past the end
+            # of the token list and raise a bare IndexError.
+            if len(elements) < COMMAND_NUM_ARGS[command]:
+                raise ValueError("Invalid path string: command '%s' expects %d "
+                                 "values but only %d remain in %r" % (
+                                     command, COMMAND_NUM_ARGS[command],
+                                     len(elements), pathdef))
+
             if command == 'M':
                 # Moveto command.
                 x = elements.pop()
@@ -3297,7 +3310,7 @@ def _parse_path(self, pathdef, current_pos=0j, tree_element=None):
                 # Smooth curve. First control point is the "reflection" of
                 # the second control point in the previous path.
 
-                if last_command not in 'CS':
+                if last_command not in ('C', 'S'):
                     # If there is no previous command or if the previous command
                     # was not an C, c, S or s, assume the first control point is
                     # coincident with the current point.
@@ -3333,7 +3346,7 @@ def _parse_path(self, pathdef, current_pos=0j, tree_element=None):
                 # Smooth curve. Control point is the "reflection" of
                 # the second control point in the previous path.
 
-                if last_command not in 'QT':
+                if last_command not in ('Q', 'T'):
                     # If there is no previous command or if the previous command
                     # was not an Q, q, T or t, assume the first control point is
                     # coincident with the current point.

test/test_parsing.py

@@ -182,6 +182,22 @@ def test_errors(self):
         self.assertRaises(ValueError, parse_path,
                           'M 100 100 L 200 200 Z 100 200')
 
+    def test_truncated_commands(self):
+        # A command missing some of its coordinates used to pop past the end of
+        # the token list and raise a bare IndexError instead of a ValueError.
+        for d in ('M', 'M 10', 'M 0 0 L', 'M 0 0 C 1 1 2 2',
+                  'H', 'V', 'Q 1 1', 'A 1 1 0 0 1'):
+            self.assertRaises(ValueError, parse_path, d)
+
+    def test_leading_smooth_command(self):
+        # A path starting with a smooth command (S/T) has no previous control
+        # point to reflect; the first control point coincides with the current
+        # point. This used to raise a TypeError from ``None in 'CS'``.
+        self.assertEqual(parse_path('S 1 1 2 2'),
+                         Path(CubicBezier(0j, 0j, 1 + 1j, 2 + 2j)))
+        self.assertEqual(parse_path('T 1 1'),
+                         Path(QuadraticBezier(0j, 0j, 1 + 1j)))
+
 
     def test_transform(self):