refactor(fstring): make whole decimal spec optional

src/core/format_spec/parser.py

@@ -86,7 +86,7 @@ class FormatSpecParser:
 
     def number(self) -> FormatSpecNumber:
         integral: FormatSpecIntegral = self.integral()
-        decimal: FormatSpecDecimal = self.decimal()
+        decimal: Optional[FormatSpecDecimal] = self.decimal()
         return FormatSpecNumber(integral=integral, decimal=decimal)
 
     def integral(self) -> FormatSpecIntegral:
@@ -101,15 +101,18 @@ class FormatSpecParser:
             grouping=grouping
         )
 
-    def decimal(self) -> FormatSpecDecimal:
+    def decimal(self) -> Optional[FormatSpecDecimal]:
+        if not self.match(TokenType.DOT):
+            return None
+        dot: Token = self.previous()
         precision: Optional[int] = None
         grouping: Optional[Token] = None
-        if self.match(TokenType.DOT):
-            if self.match(TokenType.NUMBER):
-                precision = self.previous().value
-            if self.match(TokenType.COMMA, TokenType.UNDERSCORE):
-                grouping = self.previous()
+        if self.match(TokenType.NUMBER):
+            precision = self.previous().value
+        if self.match(TokenType.COMMA, TokenType.UNDERSCORE):
+            grouping = self.previous()
         return FormatSpecDecimal(
+            dot=dot,
             precision=precision,
             grouping=grouping
         )

src/core/format_spec/spec.py

@@ -17,6 +17,7 @@ class FormatSpecIntegral:
 
 @dataclass(frozen=True)
 class FormatSpecDecimal:
+    dot: Token
     precision: Optional[int]
     grouping: Optional[Token]
 
@@ -24,7 +25,7 @@ class FormatSpecDecimal:
 @dataclass(frozen=True)
 class FormatSpecNumber:
     integral: FormatSpecIntegral
-    decimal: FormatSpecDecimal
+    decimal: Optional[FormatSpecDecimal]
 
 
 @dataclass(frozen=True)

src/formatter.py

@@ -200,7 +200,7 @@ class Formatter(Expr.Visitor[str], Stmt.Visitor[str]):
             res += str(spec.number.integral.width)
         if spec.number.integral.grouping is not None:
             res += spec.number.integral.grouping.lexeme
-        if spec.number.decimal.precision is not None or spec.number.decimal.grouping is not None:
+        if spec.number.decimal is not None:
             res += "."
             if spec.number.decimal.precision is not None:
                 res += str(spec.number.decimal.precision)