fix: ensure indent-seq works in nested collections

When {spaces: consistent, indent-sequences: true} (the defaults),
and the expected indent for a block sequence that should be indented
is unknown, set the expected indent to an unknown value (-1) rather
than an arbitrary one (2). This ensures wrong-indentation is properly
caught when block sequences are nested.

Fixes issue #485

tests/rules/test_indentation.py

@@ -1370,6 +1370,45 @@ class IndentationTestCase(RuleTestCase):
                    '               key: value\n'
                    '...\n', conf, problem=(2, 2))
 
+    def test_nested_collections_with_spaces_consistent(self):
+        """Tests behavior of {spaces: consistent} in nested collections to
+        ensure wrong-indentation is properly caught--especially when the
+        expected indent value is initially unkown. For details, see
+        https://github.com/adrienverge/yamllint/issues/485.
+        """
+        conf = ('indentation: {spaces: consistent,\n'
+                '              indent-sequences: true}')
+        self.check('---\n'
+                   '- item:\n'
+                   '  - elem\n'
+                   '- item:\n'
+                   '    - elem\n'
+                   '...\n', conf, problem=(3, 3))
+        conf = ('indentation: {spaces: consistent,\n'
+                '              indent-sequences: false}')
+        self.check('---\n'
+                   '- item:\n'
+                   '  - elem\n'
+                   '- item:\n'
+                   '    - elem\n'
+                   '...\n', conf, problem=(5,5))
+        conf = ('indentation: {spaces: consistent,\n'
+                '              indent-sequences: consistent}')
+        self.check('---\n'
+                   '- item:\n'
+                   '  - elem\n'
+                   '- item:\n'
+                   '    - elem\n'
+                   '...\n', conf, problem=(5,5))
+        conf = ('indentation: {spaces: consistent,\n'
+                '              indent-sequences: whatever}')
+        self.check('---\n'
+                   '- item:\n'
+                   '  - elem\n'
+                   '- item:\n'
+                   '    - elem\n'
+                   '...\n', conf)
+
     def test_return(self):
         conf = 'indentation: {spaces: consistent}'
         self.check('---\n'

yamllint/rules/indentation.py

@@ -341,9 +341,14 @@ def _check(conf, token, prev, next, nextnext, context):
             expected = detect_indent(expected, token)
 
         if found_indentation != expected:
-            yield LintProblem(token.start_mark.line + 1, found_indentation + 1,
-                              'wrong indentation: expected %d but found %d' %
-                              (expected, found_indentation))
+            if expected < 0:
+                message = 'wrong indentation: expected at least %d' % \
+                          (found_indentation + 1)
+            else:
+                message = 'wrong indentation: expected %d but found %d' % \
+                          (expected, found_indentation)
+            yield LintProblem(token.start_mark.line + 1,
+                              found_indentation + 1, message)
 
     if (isinstance(token, yaml.ScalarToken) and
             conf['check-multi-line-strings']):
@@ -493,8 +498,8 @@ def _check(conf, token, prev, next, nextnext, context):
                         # indentation it should have (because `spaces` is
                         # `consistent` and its value has not been computed yet
                         # -- this is probably the beginning of the document).
-                        # So we choose an arbitrary value (2).
-                        indent = 2
+                        # So we choose an unknown value (-1).
+                        indent = -1
                     else:
                         indent = detect_indent(context['stack'][-1].indent,
                                                next)