Pass through source position information in spans

Prior to this change, we were tracking source position information in
the stream, but were not storing it in the resulting spans.

This change adds start_position and end_position SourcePosition
attributes to Span nodes. To make this work we end up complicating the
constructor for Span nodes, so that it can either take a location or an
index/position combo (for JSON deserialization).

fluent.syntax/fluent/syntax/ast.py

@@ -388,18 +388,47 @@ def __init__(self, row_index: int, column_index: int, **kwargs: Any):
         self.column_index = column_index
 
 class Span(BaseNode):
-    def __init__(self, start: Location, end: Location, **kwargs: Any):
+    def __init__(
+        self,
+        start: Location | int,
+        end: Location | int,
+        start_position: SourcePosition | None = None,
+        end_position: SourcePosition | None = None,
+        **kwargs: Any,
+    ):
         super().__init__(**kwargs)
-        self.start = start
-        self.end = end
+
+        # We support two forms of arguments to the constructor. This is to allow the parser to use
+        # Location tuples for convenience, but to allow position objects to be passed during json
+        # deserialization
+        start_index, start_position = self._coerce_location_and_position(start, start_position)
+        end_index, end_position = self._coerce_location_and_position(end, end_position)
+
+        self.start = start_index
+        self.end = end_index
+        self.start_position = start_position
+        self.end_position = end_position
+
+    def _coerce_location_and_position(
+        self,
+        location_or_index: Location | int,
+        position: SourcePosition | None,
+    ) -> tuple[int, SourcePosition]:
+        if isinstance(location_or_index, int):
+            assert position is not None, "position must be passed if location is not passed"
+            return location_or_index, position
+        else:
+            assert position is None, "position must not be passed if location is passed"
+            index, row, column = location_or_index
+            return index, SourcePosition(row, column)
 
     @property
     def start_location(self) -> Location:
-        return self.start
+        return self.start, self.start_position.row_index, self.start_position.column_index
 
     @property
     def end_location(self) -> Location:
-        return self.end
+        return self.end, self.end_position.row_index, self.end_position.column_index
 
 
 class Annotation(SyntaxNode):

fluent.syntax/fluent/syntax/parser.py

@@ -85,7 +85,7 @@ def parse(self, source: str) -> ast.Resource:
         res = ast.Resource(entries)
 
         if self.with_spans:
-            res.add_span(0, ps.current_location)
+            res.add_span((0, 0, 0), ps.current_location)
 
         return res
 

fluent.syntax/fluent/syntax/stream.py

@@ -7,7 +7,9 @@
 
 # Represents a location in the parser stream (for convenience)
 # - Index
-Location: TypeAlias = int
+# - Row index (in source)
+# - Column index (in source)
+Location: TypeAlias = tuple[int, int, int]
 
 
 class ParserStream:
@@ -38,7 +40,7 @@ def char_at(self, offset: int) -> Union[str, None]:
 
     @property
     def current_location(self) -> Location:
-        return self.index
+        return self.index, self.row_index, self.column_index
 
     @property
     def current_char(self) -> Union[str, None]:

fluent.syntax/tests/syntax/test_entry.py

@@ -65,7 +65,21 @@ def test_return_junk(self):
                     "arguments": ["="],
                     "code": "E0003",
                     "message": 'Expected token: "="',
-                    "span": {"end": 23, "start": 23, "type": "Span"},
+                    "span": {
+                        "end": 23,
+                        "start": 23,
+                        "end_position": {
+                            "column_index": 4,
+                            "row_index": 1,
+                            "type": "SourcePosition",
+                        },
+                        "start_position": {
+                            "column_index": 4,
+                            "row_index": 1,
+                            "type": "SourcePosition",
+                        },
+                        "type": "Span"
+                    },
                     "type": "Annotation",
                 }
             ],
@@ -111,7 +125,21 @@ def test_do_not_ignore_invalid_comments(self):
                     "arguments": [" "],
                     "code": "E0003",
                     "message": 'Expected token: " "',
-                    "span": {"end": 21, "start": 21, "type": "Span"},
+                    "span": {
+                        "end": 21,
+                        "start": 21,
+                        "end_position": {
+                            "column_index": 2,
+                            "row_index": 1,
+                            "type": "SourcePosition",
+                        },
+                        "start_position": {
+                            "column_index": 2,
+                            "row_index": 1,
+                            "type": "SourcePosition",
+                        },
+                        "type": "Span",
+                    },
                     "type": "Annotation",
                 }
             ],

fluent.syntax/tests/syntax/test_visitor.py

@@ -44,6 +44,7 @@ def test_resource(self):
                 "Identifier": 4,
                 "Attribute": 1,
                 "Span": 10,
+                "SourcePosition": 20,
             },
         )