(fluent.syntax) Don't drop to newline when serializing patterns starting with special chars

fluent.syntax/fluent/syntax/serializer.py

@@ -2,7 +2,7 @@
 from . import ast
 
 
-def indent(content):
+def indent_except_first_line(content):
     return "    ".join(
         content.splitlines(True)
     )
@@ -18,6 +18,20 @@ def is_select_expr(elem):
         isinstance(elem.expression, ast.SelectExpression))
 
 
+def should_start_on_new_line(pattern):
+    is_multiline = any(is_select_expr(elem) for elem in pattern.elements) \
+        or any(includes_new_line(elem) for elem in pattern.elements)
+
+    if is_multiline:
+        first_element = pattern.elements[0]
+        if isinstance(first_element, ast.TextElement):
+            first_char = first_element.value[0]
+            if first_char in ("[", ".", "*"):
+                return False
+        return True
+    return False
+
+
 class FluentSerializer(object):
     """FluentSerializer converts :class:`.ast.SyntaxNode` objects to unicode strings.
 
@@ -119,19 +133,16 @@ def serialize_term(term):
 def serialize_attribute(attribute):
     return "\n    .{} ={}".format(
         attribute.id.name,
-        indent(serialize_pattern(attribute.value))
+        indent_except_first_line(serialize_pattern(attribute.value))
     )
 
 
 def serialize_pattern(pattern):
-    content = "".join([
-        serialize_element(elem)
-        for elem in pattern.elements])
-    start_on_new_line = any(
-        includes_new_line(elem) or is_select_expr(elem)
-        for elem in pattern.elements)
-    if start_on_new_line:
-        return '\n    {}'.format(indent(content))
+    content = "".join(serialize_element(elem) for elem in pattern.elements)
+    content = indent_except_first_line(content)
+
+    if should_start_on_new_line(pattern):
+        return '\n    {}'.format(content)
 
     return ' {}'.format(content)
 
@@ -193,7 +204,7 @@ def serialize_variant(variant):
     return "\n{}[{}]{}".format(
         "   *" if variant.default else "    ",
         serialize_variant_key(variant.key),
-        indent(serialize_pattern(variant.value))
+        indent_except_first_line(serialize_pattern(variant.value))
     )
 
 

fluent.syntax/tests/syntax/fixtures_reference/special_chars.ftl

@@ -0,0 +1,14 @@
+## OK
+
+bracket-inline = [Value]
+dot-inline = .Value
+star-inline = *Value
+
+## ERRORS
+
+bracket-newline =
+    [Value]
+dot-newline =
+    .Value
+star-newline =
+    *Value

fluent.syntax/tests/syntax/fixtures_reference/special_chars.json

@@ -0,0 +1,82 @@
+{
+    "type": "Resource",
+    "body": [
+        {
+            "type": "GroupComment",
+            "content": "OK"
+        },
+        {
+            "type": "Message",
+            "id": {
+                "type": "Identifier",
+                "name": "bracket-inline"
+            },
+            "value": {
+                "type": "Pattern",
+                "elements": [
+                    {
+                        "type": "TextElement",
+                        "value": "[Value]"
+                    }
+                ]
+            },
+            "attributes": [],
+            "comment": null
+        },
+        {
+            "type": "Message",
+            "id": {
+                "type": "Identifier",
+                "name": "dot-inline"
+            },
+            "value": {
+                "type": "Pattern",
+                "elements": [
+                    {
+                        "type": "TextElement",
+                        "value": ".Value"
+                    }
+                ]
+            },
+            "attributes": [],
+            "comment": null
+        },
+        {
+            "type": "Message",
+            "id": {
+                "type": "Identifier",
+                "name": "star-inline"
+            },
+            "value": {
+                "type": "Pattern",
+                "elements": [
+                    {
+                        "type": "TextElement",
+                        "value": "*Value"
+                    }
+                ]
+            },
+            "attributes": [],
+            "comment": null
+        },
+        {
+            "type": "GroupComment",
+            "content": "ERRORS"
+        },
+        {
+            "type": "Junk",
+            "annotations": [],
+            "content": "bracket-newline =\n    [Value]\n"
+        },
+        {
+            "type": "Junk",
+            "annotations": [],
+            "content": "dot-newline =\n    .Value\n"
+        },
+        {
+            "type": "Junk",
+            "annotations": [],
+            "content": "star-newline =\n    *Value\n"
+        }
+    ]
+}

fluent.syntax/tests/syntax/test_serializer.py

@@ -139,12 +139,31 @@ def test_comment_standalone(self):
         input = """\
             foo = Foo
 
-            # A multiline
+            # A standalone comment
 
             bar = Bar
         """
         self.assertEqual(self.pretty_ftl(input), dedent_ftl(input))
 
+    def test_multiline_starting_inline(self):
+        input = """\
+            foo = Foo
+                Bar
+        """
+        output = """\
+            foo =
+                Foo
+                Bar
+        """
+        self.assertEqual(self.pretty_ftl(input), dedent_ftl(output))
+
+    def test_multiline_starting_inline_with_special_char(self):
+        input = """\
+            foo = *Foo
+                Bar
+        """
+        self.assertEqual(self.pretty_ftl(input), dedent_ftl(input))
+
     def test_multiline_with_placeable(self):
         input = """\
             foo =
@@ -269,6 +288,15 @@ def test_select_expression_in_inline_value(self):
         """
         self.assertEqual(self.pretty_ftl(input), dedent_ftl(output))
 
+    def test_select_expression_in_inline_value_starting_with_special_char(self):
+        input = """\
+            foo = .Foo { $sel ->
+                   *[a] A
+                    [b] B
+                }
+        """
+        self.assertEqual(self.pretty_ftl(input), dedent_ftl(input))
+
     def test_select_expression_in_multi_multiline(self):
         input = """\
             foo =