Handle Jinja whitespace control syntax

It doesn’t exist in the Django flavor.

jinjalint/ast.py

@@ -11,7 +11,7 @@ def __str__(self):
         return '{}:{}'.format(self.line + 1, self.column)
 
 
-@attr.s
+@attr.s(frozen=True)
 class Node:
     begin = attr.ib()  # Location
     end = attr.ib()  # Location
@@ -27,7 +27,7 @@ def __str__(self):
 class OpeningTag(Node):
     name = attr.ib()
     attributes = attr.ib()  # Interpolated<Attribute>
-    slash = attr.ib(default=None)  # Slash | None
+    slash = attr.ib(default=None)  # Slash | None (`Slash` if self-closing tag)
 
     def __str__(self):
         name = str(self.name)
@@ -123,9 +123,21 @@ class Jinja(Node):
 @attr.s(frozen=True)
 class JinjaVariable(Jinja):
     content = attr.ib()  # str
+    left_plus = attr.ib(default=False)
+    left_minus = attr.ib(default=False)
+    right_minus = attr.ib(default=False)
 
     def __str__(self):
-        return '{{ ' + self.content + ' }}'
+        return ''.join([
+            '{{',
+            '+' if self.left_plus else '',
+            '-' if self.left_minus else '',
+            ' ',
+            self.content,
+            ' ',
+            '-' if self.right_minus else '',
+            '}}'
+        ])
 
 
 @attr.s(frozen=True)
@@ -140,13 +152,21 @@ def __str__(self):
 class JinjaTag(Jinja):
     name = attr.ib()
     content = attr.ib()  # str | None
+    left_plus = attr.ib(default=False)
+    left_minus = attr.ib(default=False)
+    right_minus = attr.ib(default=False)
 
     def __str__(self):
-        s = '{% ' + self.name
-        if self.content:
-            s += ' ' + self.content
-
-        return s + ' %}'
+        return ''.join([
+            '{%',
+            '+' if self.left_plus else '',
+            '-' if self.left_minus else '',
+            (' ' + self.name) if self.name else '',
+            (' ' + self.content) if self.content else '',
+            ' ',
+            '-' if self.right_minus else '',
+            '%}'
+        ])
 
 
 @attr.s(frozen=True)

jinjalint/parse.py

@@ -83,17 +83,22 @@ def locate(parser):
 
 
 def _combine_jinja_tag(locations, props):
-    head, name, content, tail = props
     return JinjaTag(
-        name=name,
-        content=content,
+        name=props['name'],
+        content=props['extra_content'],
+        left_plus=props['left_plus'],
+        left_minus=props['left_minus'],
+        right_minus=props['right_minus'],
         **locations,
     )
 
 
-def _combine_jinja_variable(locations, content):
+def _combine_jinja_variable(locations, props):
     return JinjaVariable(
-        content=content,
+        content=props['extra_content'],
+        left_plus=props['left_plus'],
+        left_minus=props['left_minus'],
+        right_minus=props['right_minus'],
         **locations,
     )
 
@@ -105,15 +110,39 @@ def _combine_jinja_comment(locations, text):
     )
 
 
-jinja_variable = (
-    locate(
-        P.string('{{')
-        .skip(whitespace)
-        .then(until(whitespace + P.string('}}')).concat())
-        .skip(whitespace + P.string('}}'))
+def _combine_jinja_tag_like(locations, props):
+    return (
+        locations,
+        {
+            'left_plus': props['left_plus'] is not None,
+            'left_minus': props['left_minus'] is not None,
+            'name': props['name'],
+            'extra_content': props['extra_content'],
+            'right_minus': props['right_minus'] is not None,
+        }
     )
-    .combine(_combine_jinja_variable)
-)
+
+
+def make_jinja_tag_like_parser(name, ml='{', mr='}'):
+    """
+    Create parsers for Jinja variables and regular Jinja tags.
+
+    `name` should be a parser to parse the tag name.
+    """
+    end = whitespace.then(P.string('-').optional()).skip(P.string(mr + '}'))
+    return locate(P.seq(
+        left_plus=P.string('{' + ml).then(P.string('+').optional()),
+        left_minus=P.string('-').optional().skip(whitespace),
+        name=name.skip(whitespace),
+        extra_content=until(end).concat(),
+        right_minus=end
+    )).combine(_combine_jinja_tag_like)
+
+
+jinja_variable = make_jinja_tag_like_parser(
+    P.success(None), '{', '}'
+).combine(_combine_jinja_variable)
+
 
 jinja_comment = (
     locate(
@@ -128,14 +157,7 @@ def _combine_jinja_comment(locations, text):
 
 def make_jinja_tag_parser(name_parser):
     return (
-        locate(
-            P.seq(
-                P.string('{%') + whitespace,
-                name_parser.skip(whitespace),
-                until(whitespace + P.string('%}')).concat(),
-                whitespace + P.string('%}'),
-            )
-        )
+        make_jinja_tag_like_parser(name_parser, '%', '%')
         .combine(_combine_jinja_tag)
     )
 

jinjalint/parse_test.py

@@ -42,10 +42,14 @@ def create_node(*args, **kwargs):
         kwargs['begin'] = DummyLocation()
         kwargs['end'] = DummyLocation()
 
-        return node_class(
-            *args,
-            **kwargs,
-        )
+        try:
+            return node_class(
+                *args,
+                **kwargs,
+            )
+        except Exception as error:
+            print(node_class)
+            raise error
 
     return create_node
 
@@ -350,6 +354,30 @@ def test_jinja_blocks():
     assert src == str(jinja.parse(src))
 
 
+def test_jinja_whitespace_controls():
+    assert jinja.parse('{%- foo -%}') == JinjaElement(
+        parts=[
+            JinjaElementPart(
+                tag=JinjaTag(
+                    name='foo',
+                    content='',
+                    left_minus=True,
+                    right_minus=True,
+                ),
+                content=None,
+            ),
+        ],
+        closing_tag=None,
+    )
+
+    assert str(jinja.parse('{%- foo -%}')) == '{%- foo -%}'
+    assert str(jinja.parse('{%- foo %}')) == '{%- foo %}'
+    assert str(jinja.parse('{{- bar -}}')) == '{{- bar -}}'
+    assert str(jinja.parse('{{ bar -}}')) == '{{ bar -}}'
+    assert str(jinja.parse('{%+ foo %}')) == '{%+ foo %}'
+    assert str(jinja.parse('{{+ bar }}')) == '{{+ bar }}'
+
+
 def test_doctype():
     assert content.parse('<!DOCTYPE html>') == Interp('<!DOCTYPE html>')
 
@@ -394,6 +422,7 @@ def test():
     test_element()
     test_self_closing_elements()
     test_jinja_blocks()
+    test_jinja_whitespace_controls()
     test_doctype()
     test_attrs()
     test_optional_container()