fix: load negative integer literals as numbers (#307)

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Restore `py.typed` marker so type checkers recognize `hcl2` (and `cli`) as typed packages. ([#298](https://github.com/amplify-education/python-hcl2/issues/298))
 - Parse heredocs with an empty body again. A marker immediately followed by its closing delimiter failed to match, and the lexer then ran on to a later delimiter, silently absorbing the attributes in between. ([#309](https://github.com/amplify-education/python-hcl2/issues/309))
+- Negative integer literals load as numbers again instead of `${-N}` expression strings, matching negative floats and the pre-8.x behaviour. ([#307](https://github.com/amplify-education/python-hcl2/issues/307))
 
 ## \[8.1.2\] - 2026-04-10
 

hcl2/rules/expressions.py

@@ -1,7 +1,7 @@
 """Rule classes for HCL2 expressions, conditionals, and binary/unary operations."""
 
 from abc import ABC
-from typing import Any, Optional, Tuple
+from typing import Any, Optional, Tuple, Union
 
 from lark.tree import Meta
 
@@ -305,12 +305,41 @@ def serialize(self, options=SerializationOptions(), context=SerializationContext
         """Serialize to 'operator operand' string."""
         with context.modify(inside_dollar_string=True):
             operator = self.operator.rstrip()
-            result = f"{operator}{self.expr_term.serialize(options, context)}"
+            operand = self.expr_term.serialize(options, context)
+            result = f"{operator}{operand}"
 
         if not context.inside_dollar_string:
+            # A negated numeric literal is a number, not an expression. The
+            # lexer splits `-3` into MINUS and INT_LITERAL because MINUS is also
+            # the binary operator (`1 -3` must stay a subtraction), so negative
+            # integers arrive here rather than as a single token. Recombining
+            # them keeps `-3` an int, matching `-3.5`, which FLOAT_LITERAL
+            # already matches whole.
+            negated = self._negate_numeric_literal(operator, operand, options)
+            if negated is not None:
+                return negated
             result = to_dollar_string(result)
 
         if options.force_operation_parentheses:
             result = self._wrap_into_parentheses(result, options, context)
 
         return result
+
+    @staticmethod
+    def _negate_numeric_literal(
+        operator: str, operand: Any, options: SerializationOptions
+    ) -> Optional[Union[int, float]]:
+        """Return the negated value when this is `-` applied to a number.
+
+        Returns None when the operation is anything else, so that the caller
+        falls back to the `${...}` expression form: `-var.x` has no literal
+        value, `!flag` is not arithmetic, and a scientific-notation operand
+        serializes to a string when `preserve_scientific_notation` is set.
+        Parenthesised output is likewise left alone, since a bare number cannot
+        carry the parentheses that option asks for.
+        """
+        if operator != "-" or options.force_operation_parentheses:
+            return None
+        if isinstance(operand, bool) or not isinstance(operand, (int, float)):
+            return None
+        return -operand

test/integration/hcl2_original/integers.tf

@@ -0,0 +1,20 @@
+locals {
+  simple_int = 123
+  zero = 0
+  large_int = 9876543210
+  negative_int = -42
+  negative_one = -1
+  negative_large = -9876543210
+  negative_zero = -0
+  negated_keyword = -true
+  int_calculation = 105 * 3 / 2
+  int_subtraction = 10 - 3
+  int_negated_reference = -var.count
+  int_comparison = 5 > 2 ? 1 : 0
+  int_list = [1, 2, 3, -4, -5]
+  int_object = {
+    positive = 7
+    negative = -7
+    mixed = [-1, 0, 1]
+  }
+}

test/integration/hcl2_reconstructed/integers.tf

@@ -0,0 +1,30 @@
+locals {
+  simple_int            = 123
+  zero                  = 0
+  large_int             = 9876543210
+  negative_int          = -42
+  negative_one          = -1
+  negative_large        = -9876543210
+  negative_zero         = 0
+  negated_keyword       = -true
+  int_calculation       = 105 * 3 / 2
+  int_subtraction       = 10 - 3
+  int_negated_reference = -var.count
+  int_comparison        = 5 > 2 ? 1 : 0
+  int_list              = [
+    1,
+    2,
+    3,
+    -4,
+    -5,
+  ]
+  int_object            = {
+    positive = 7,
+    negative = -7,
+    mixed    = [
+      -1,
+      0,
+      1,
+    ],
+  }
+}

test/integration/json_reserialized/integers.json

@@ -0,0 +1,35 @@
+{
+  "locals": [
+    {
+      "simple_int": 123,
+      "zero": 0,
+      "large_int": 9876543210,
+      "negative_int": -42,
+      "negative_one": -1,
+      "negative_large": -9876543210,
+      "negative_zero": 0,
+      "negated_keyword": "${-true}",
+      "int_calculation": "${105 * 3 / 2}",
+      "int_subtraction": "${10 - 3}",
+      "int_negated_reference": "${-var.count}",
+      "int_comparison": "${5 > 2 ? 1 : 0}",
+      "int_list": [
+        1,
+        2,
+        3,
+        -4,
+        -5
+      ],
+      "int_object": {
+        "positive": 7,
+        "negative": -7,
+        "mixed": [
+          -1,
+          0,
+          1
+        ]
+      },
+      "__is_block__": true
+    }
+  ]
+}

test/integration/json_serialized/integers.json

@@ -0,0 +1,35 @@
+{
+  "locals": [
+    {
+      "simple_int": 123,
+      "zero": 0,
+      "large_int": 9876543210,
+      "negative_int": -42,
+      "negative_one": -1,
+      "negative_large": -9876543210,
+      "negative_zero": 0,
+      "negated_keyword": "${-true}",
+      "int_calculation": "${105 * 3 / 2}",
+      "int_subtraction": "${10 - 3}",
+      "int_negated_reference": "${-var.count}",
+      "int_comparison": "${5 > 2 ? 1 : 0}",
+      "int_list": [
+        1,
+        2,
+        3,
+        -4,
+        -5
+      ],
+      "int_object": {
+        "positive": 7,
+        "negative": -7,
+        "mixed": [
+          -1,
+          0,
+          1
+        ]
+      },
+      "__is_block__": true
+    }
+  ]
+}

test/unit/rules/test_expressions.py

@@ -424,6 +424,69 @@ def test_serialize_force_parens_with_expression_parent(self):
         self.assertEqual(result, "${(-x)}")
 
 
+class TestUnaryOpRuleNegativeNumbers(TestCase):
+    """`-3` is the number -3, not the expression string "${-3}".
+
+    The lexer cannot fold the sign into INT_LITERAL, because MINUS is also the
+    binary subtraction operator and `10 -3` has to stay a subtraction, so a
+    negative integer reaches serialization as MINUS applied to a literal.
+    """
+
+    def _make_unary(self, op_str, operand_val):
+        token_cls = MINUS_TOKEN if op_str == "-" else NOT_TOKEN
+        return UnaryOpRule([token_cls(op_str), _make_expr_term(operand_val)])
+
+    def test_negative_int_serializes_to_int(self):
+        rule = self._make_unary("-", 3)
+        self.assertEqual(rule.serialize(), -3)
+
+    def test_negative_zero_serializes_to_int(self):
+        rule = self._make_unary("-", 0)
+        self.assertEqual(rule.serialize(), 0)
+
+    def test_negative_float_serializes_to_float(self):
+        rule = self._make_unary("-", 3.5)
+        self.assertEqual(rule.serialize(), -3.5)
+
+    def test_negated_identifier_stays_an_expression(self):
+        rule = self._make_unary("-", "var.count")
+        self.assertEqual(rule.serialize(), "${-var.count}")
+
+    def test_not_operator_is_untouched(self):
+        rule = self._make_unary("!", 1)
+        self.assertEqual(rule.serialize(), "${!1}")
+
+    def test_inside_dollar_string_stays_text(self):
+        """Within a larger expression the operand must remain concatenable."""
+        rule = self._make_unary("-", 3)
+        ctx = SerializationContext(inside_dollar_string=True)
+        self.assertEqual(rule.serialize(context=ctx), "-3")
+
+    def test_force_parens_keeps_expression_form(self):
+        """A bare number cannot carry the parentheses that option requests."""
+        rule = self._make_unary("-", 3)
+        opts = SerializationOptions(force_operation_parentheses=True)
+        self.assertEqual(rule.serialize(options=opts), "${-3}")
+
+    def test_boolean_operand_is_not_treated_as_a_number(self):
+        """`bool` subclasses `int`, so without the guard `-true` would serialize to -1.
+
+        Asserted against the helper rather than `serialize()`: no HCL input can
+        route a Python bool here, because `UnaryOpRule` serializes its operand
+        with `inside_dollar_string` set, and `LiteralValueRule` yields the string
+        "true" in that context. See `TestNegatedKeywords` for the parsed path.
+        """
+        options = SerializationOptions()
+        self.assertIsNone(UnaryOpRule._negate_numeric_literal("-", True, options))
+        self.assertIsNone(UnaryOpRule._negate_numeric_literal("-", False, options))
+
+    def test_zero_operand_returns_zero_not_none(self):
+        """The caller must test `is not None`; plain truthiness would drop `-0`."""
+        result = UnaryOpRule._negate_numeric_literal("-", 0, SerializationOptions())
+        self.assertEqual(result, 0)
+        self.assertIsNotNone(result)
+
+
 # --- ExpressionRule._wrap_into_parentheses tests ---
 
 

test/unit/test_api.py

@@ -359,3 +359,90 @@ def test_empty_heredoc_as_an_object_value(self):
 
     def test_empty_heredoc_as_a_function_argument(self):
         self.assertEqual(loads("a = trimspace(<<EOF\nEOF\n)\n"), {"a": '${trimspace("<<EOF\nEOF")}'})
+
+
+class TestNegativeIntegerLiterals(TestCase):
+    """`-3` loads as the int -3, without disturbing subtraction.
+
+    MINUS serves as both the unary sign and the binary subtraction operator, so
+    a negative integer cannot be folded into INT_LITERAL by the lexer without
+    breaking `10 -3`. These cases pin both halves of that trade-off.
+    """
+
+    def test_negative_int_is_an_int(self):
+        self.assertEqual(loads("x = -3\n"), {"x": -3})
+
+    def test_negative_int_matches_negative_float_handling(self):
+        self.assertEqual(loads("x = -3\ny = -3.5\n"), {"x": -3, "y": -3.5})
+
+    def test_negative_ints_in_tuple(self):
+        self.assertEqual(loads("x = [-1, 2, -30]\n"), {"x": [-1, 2, -30]})
+
+    def test_negative_ints_in_object(self):
+        self.assertEqual(loads("x = { a = -1, b = 2 }\n"), {"x": {"a": -1, "b": 2}})
+
+    def test_spaced_subtraction_is_still_an_expression(self):
+        self.assertEqual(loads("x = 10 - 3\n"), {"x": "${10 - 3}"})
+
+    def test_tight_subtraction_is_still_an_expression(self):
+        """`10 -3` is a subtraction, not two adjacent literals."""
+        self.assertEqual(loads("x = 10 -3\n"), {"x": "${10 - 3}"})
+
+    def test_negated_reference_is_still_an_expression(self):
+        self.assertEqual(loads("x = -var.count\n"), {"x": "${-var.count}"})
+
+    def test_negation_inside_a_larger_expression(self):
+        self.assertEqual(loads("x = 1 + -3\n"), {"x": "${1 + -3}"})
+
+    def test_parenthesised_negation_is_still_an_expression(self):
+        self.assertEqual(loads("x = -(3)\n"), {"x": "${-(3)}"})
+
+    def test_scientific_notation_is_unaffected(self):
+        """`-1e10` never reaches the unary path: it lexes as a single FLOAT_LITERAL."""
+        self.assertEqual(loads("x = -1e10\n"), {"x": "${-1e10}"})
+
+    def test_spaced_negation_of_scientific_notation_stays_an_expression(self):
+        """The spaced form *is* a unary op, and its operand is a string.
+
+        `preserve_scientific_notation` (on by default) keeps `1e10` as source
+        text, so there is no number to negate and the expression form stands.
+        """
+        self.assertEqual(loads("x = - 1e10\n"), {"x": "${-1e10}"})
+
+    def test_spaced_negation_of_integer_is_still_a_number(self):
+        self.assertEqual(loads("x = - 3\n"), {"x": -3})
+
+    def test_negative_zero_normalises_to_zero(self):
+        """`-0` is 0. The dict path drops the sign; the direct path keeps the source."""
+        self.assertEqual(loads("x = -0\n"), {"x": 0})
+        self.assertEqual(dumps(loads("x = -0\n")), "x = 0\n")
+
+    def test_round_trip_through_dumps(self):
+        self.assertEqual(loads(dumps(loads("x = -3\n"))), {"x": -3})
+
+
+class TestNegatedKeywords(TestCase):
+    """`-true` is not arithmetic, so it stays an expression.
+
+    This is the parsed counterpart to the `bool` guard in
+    `UnaryOpRule._negate_numeric_literal`: a keyword operand is serialized with
+    `inside_dollar_string` set and so arrives as the string "true", never as a
+    Python bool. Without that distinction `bool` subclassing `int` would turn
+    `-true` into -1.
+    """
+
+    def test_negated_true(self):
+        self.assertEqual(loads("x = -true\n"), {"x": "${-true}"})
+
+    def test_negated_false(self):
+        self.assertEqual(loads("x = -false\n"), {"x": "${-false}"})
+
+    def test_negated_null(self):
+        self.assertEqual(loads("x = -null\n"), {"x": "${-null}"})
+
+    def test_not_operator_on_keyword(self):
+        self.assertEqual(loads("x = !true\n"), {"x": "${!true}"})
+
+    def test_bare_keywords_are_still_python_values(self):
+        """Outside an expression the keywords keep their Python mappings."""
+        self.assertEqual(loads("x = true\ny = false\nz = null\n"), {"x": True, "y": False, "z": None})