ezt: detect unmatched else tags (#11581)

tests/test_ezt.py

@@ -1,6 +1,6 @@
 import pytest
 from StringIO import StringIO
-from wcs.qommon.ezt import Template, UnclosedBlocksError, UnmatchedEndError
+from wcs.qommon.ezt import Template, UnclosedBlocksError, UnmatchedEndError, UnmatchedElseError
 
 def test_simple_qualifier():
     template = Template()
@@ -91,6 +91,15 @@ def test_unmatched_end():
     except UnmatchedEndError as e:
         assert e.column == 15 and e.line == 0
 
+def test_unmatched_else():
+    template = Template()
+    with pytest.raises(UnmatchedElseError):
+        template.parse('<p>[else]</p>')
+    try:
+        template.parse('<p>[else]</p>')
+    except UnmatchedElseError as e:
+        assert e.column == 3 and e.line == 0
+
 def test_array_index():
     template = Template()
     template.parse('<p>[foo.0]</p>')

wcs/qommon/ezt.py

@@ -377,7 +377,10 @@ class Template:
           if len(args) > 1:
             raise ArgCountSyntaxError(str(args[1:]), line, column)
           ### check: don't allow for 'for' cmd
-          idx = stack[-1][1]
+          try:
+            idx = stack[-1][1]
+          except IndexError:
+            raise UnmatchedElseError('', line, column)
           true_section = program[idx:]
           del program[idx:]
           stack[-1][3] = true_section
@@ -751,6 +754,9 @@ class UnclosedBlocksError(EZTException):
 class UnmatchedEndError(EZTException):
   """This error may be caused by a misspelled if directive."""
 
+class UnmatchedElseError(EZTException):
+  """This error may be caused by a misspelled if directive."""
+
 class BaseUnavailableError(EZTException):
   """Base location is unavailable, which disables includes."""
 

wcs/qommon/form.py

@@ -2263,11 +2263,12 @@ class ComputedExpressionWidget(StringWidget):
                 ezt.NeedSequenceError: _('sequence required'),
                 ezt.UnclosedBlocksError: _('unclosed block'),
                 ezt.UnmatchedEndError: _('unmatched [end]'),
+                ezt.UnmatchedElseError: _('unmatched [else]'),
                 ezt.BaseUnavailableError: _('unavailable base location'),
                 ezt.BadFormatConstantError: _('bad format constant'),
                 ezt.UnknownFormatConstantError: _('unknown format constant'),
                 }.get(e.__class__))
-            if e.line:
+            if e.line is not None:
                 parts.append(_('at line %(line)d and column %(column)d') % {
                     'line': e.line+1,
                     'column': e.column+1})