Inline Patterns may start with any character (#48)

`}`, `.`, `*` and `[` are only special when they appear at the beginning of indented Pattern lines. When a Pattern starts on the same line as `id =` or `[variant key]`, its first character doesn't carry any special meaning and it may be one of those four ones as well.

See also https://bugzilla.mozilla.org/show_bug.cgi?id=1436685.

Port of projectfluent/fluent.js#150.

Author: stasm

fluent/syntax/ftlstream.py

@@ -106,18 +106,18 @@ def is_number_start(self):
         self.reset_peek()
         return is_digit
 
-    def is_char_pattern_start(self, ch):
+    def is_char_pattern_continuation(self, ch):
         return ch not in SPECIAL_LINE_START_CHARS
 
     def is_peek_pattern_start(self):
         self.peek_inline_ws()
+        ch = self.current_peek()
 
-        if self.current_peek_is('\n'):
-            return self.is_peek_next_line_pattern_start()
+        # Inline Patterns may start with any char.
+        if ch is not None and ch != '\n':
+            return True
 
-        is_pattern = self.is_char_pattern_start(self.current_peek())
-        self.reset_peek()
-        return is_pattern
+        return self.is_peek_next_line_pattern_start()
 
     def is_peek_next_line_zero_four_style_comment(self):
         if not self.current_peek_is('\n'):
@@ -227,7 +227,7 @@ def is_peek_next_line_pattern_start(self):
             self.reset_peek()
             return False
 
-        if not self.is_char_pattern_start(self.current_peek()):
+        if not self.is_char_pattern_continuation(self.current_peek()):
             self.reset_peek()
             return False
 

tests/syntax/fixtures_structure/leading_dots.ftl

@@ -0,0 +1,64 @@
+key01 = .Value
+key02 = …Value
+key03 = {"."}Value
+key04 =
+    {"."}Value
+
+key05 = Value
+    {"."}Continued
+
+key06 = .Value
+    {"."}Continued
+
+# ERROR (attr .Continued must have a value)
+key07 = Value
+    .Continued
+
+# ERROR (attr .Value must have a value)
+key08 =
+    .Value
+
+# ERROR (attr .Value must have a value)
+key09 =
+    .Value
+    Continued
+
+key10 =
+    .Value = which looks like an attribute
+    Continued
+
+key11 =
+    {"."}Value = which looks like an attribute
+    Continued
+
+key12 =
+    .accesskey =
+    A
+    
+key13 =
+    .attribute = .Value
+
+key14 =
+    .attribute =
+         {"."}Value
+
+key15 =
+    { 1 ->
+        [one] .Value
+       *[other]
+            {"."}Value
+    }
+
+# ERROR (variant must have a value)
+key16 =
+    { 1 ->
+       *[one]
+           .Value
+    }
+
+# ERROR (unclosed placeable)
+key17 =
+    { 1 ->
+       *[one] Value
+           .Continued
+    }