Preserve literals of e-notation floats in parsing and reconstruction

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Issue parsing ellipsis in a separate line within `for` expression ([#221](https://github.com/amplify-education/python-hcl2/pull/221))
 - Issue parsing inline expression as an object key; **see Limitations in README.md** ([#222](https://github.com/amplify-education/python-hcl2/pull/222))
+- Preserve literals of e-notation floats in parsing and reconstruction. Thanks, @eranor ([#226](https://github.com/amplify-education/python-hcl2/pull/226))
 
 ## \[7.1.0\] - 2025-04-10
 

hcl2/reconstructor.py

@@ -260,6 +260,7 @@ def _should_add_space(self, rule, current_terminal):
                 Terminal("STRING_LIT"),
                 Terminal("DECIMAL"),
                 Terminal("NAME"),
+                Terminal("NEGATIVE_DECIMAL"),
             ]:
                 return True
 
@@ -412,10 +413,7 @@ def _newline(self, level: int, count: int = 1) -> Tree:
     def _is_block(self, value: Any) -> bool:
         if isinstance(value, dict):
             block_body = value
-            if (
-                START_LINE_KEY in block_body.keys()
-                or END_LINE_KEY in block_body.keys()
-            ):
+            if START_LINE_KEY in block_body.keys() or END_LINE_KEY in block_body.keys():
                 return True
 
             try:
@@ -520,7 +518,7 @@ def _transform_dict_to_body(self, hcl_dict: dict, level: int) -> Tree:
 
         return Tree(Token("RULE", "body"), children)
 
-    # pylint: disable=too-many-branches, too-many-return-statements
+    # pylint: disable=too-many-branches, too-many-return-statements too-many-statements
     def _transform_value_to_expr_term(self, value, level) -> Union[Token, Tree]:
         """Transforms a value from a dictionary into an "expr_term" (a value in HCL2)
 
@@ -611,6 +609,37 @@ def _transform_value_to_expr_term(self, value, level) -> Union[Token, Tree]:
                 ],
             )
 
+        if isinstance(value, float):
+            value = str(value)
+            literal = []
+
+            if value[0] == "-":
+                # pop two first chars - minus and a digit
+                literal.append(Token("NEGATIVE_DECIMAL", value[:2]))
+                value = value[2:]
+
+            while value != "":
+                char = value[0]
+
+                if char == ".":
+                    # current char marks beginning of decimal part: pop all remaining chars and end the loop
+                    literal.append(Token("DOT", char))
+                    literal.extend(Token("DECIMAL", char) for char in value[1:])
+                    break
+
+                if char == "e":
+                    # current char marks beginning of e-notation: pop all remaining chars and end the loop
+                    literal.append(Token("EXP_MARK", value))
+                    break
+
+                literal.append(Token("DECIMAL", char))
+                value = value[1:]
+
+            return Tree(
+                Token("RULE", "expr_term"),
+                [Tree(Token("RULE", "float_lit"), literal)],
+            )
+
         # store strings as single literals
         if isinstance(value, str):
             # potentially unpack a complex syntax structure

hcl2/transformer.py

@@ -44,7 +44,10 @@ def __init__(self, with_meta: bool = False):
         super().__init__()
 
     def float_lit(self, args: List) -> float:
-        return float("".join([self.to_tf_inline(arg) for arg in args]))
+        value = "".join([self.to_tf_inline(arg) for arg in args])
+        if "e" in value:
+            return self.to_string_dollar(value)
+        return float(value)
 
     def int_lit(self, args: List) -> int:
         return int("".join([self.to_tf_inline(arg) for arg in args]))
@@ -177,7 +180,9 @@ def conditional(self, args: List) -> str:
         return f"{args[0]} ? {args[1]} : {args[2]}"
 
     def binary_op(self, args: List) -> str:
-        return " ".join([self.to_tf_inline(arg) for arg in args])
+        return " ".join(
+            [self.unwrap_string_dollar(self.to_tf_inline(arg)) for arg in args]
+        )
 
     def unary_op(self, args: List) -> str:
         args = self.process_nulls(args)
@@ -304,21 +309,31 @@ def strip_new_line_tokens(self, args: List) -> List:
         """
         return [arg for arg in args if arg != "\n" and arg is not Discard]
 
+    def is_string_dollar(self, value: str) -> bool:
+        if not isinstance(value, str):
+            return False
+        return value.startswith("${") and value.endswith("}")
+
     def to_string_dollar(self, value: Any) -> Any:
         """Wrap a string in ${ and }"""
-        if isinstance(value, str):
+        if not isinstance(value, str):
+            return value
             # if it's already wrapped, pass it unmodified
-            if value.startswith("${") and value.endswith("}"):
-                return value
+        if self.is_string_dollar(value):
+            return value
 
-            if value.startswith('"') and value.endswith('"'):
-                value = str(value)[1:-1]
-                return self.process_escape_sequences(value)
+        if value.startswith('"') and value.endswith('"'):
+            value = str(value)[1:-1]
+            return self.process_escape_sequences(value)
+
+        if self.is_type_keyword(value):
+            return value
 
-            if self.is_type_keyword(value):
-                return value
+        return f"${{{value}}}"
 
-            return f"${{{value}}}"
+    def unwrap_string_dollar(self, value: str):
+        if self.is_string_dollar(value):
+            return value[2:-1]
         return value
 
     def strip_quotes(self, value: Any) -> Any:

test/helpers/terraform-config-json/test_floats.json

@@ -0,0 +1,30 @@
+{
+ "locals": [
+  {
+   "simple_float": 123.456,
+   "small_float": 0.123,
+   "large_float": 9876543.21,
+   "negative_float": -42.5,
+   "negative_small": -0.001,
+   "scientific_positive": "${1.23e5}",
+   "scientific_negative": "${9.87e-3}",
+   "scientific_large": "${6.022e+23}",
+   "integer_as_float": 100.0,
+   "float_calculation": "${105e+2 * 3.0 / 2.1}",
+   "float_comparison": "${5e1 > 2.3 ? 1.0 : 0.0}",
+   "float_list": [
+    1.1,
+    2.2,
+    3.3,
+    -4.4,
+    "${5.5e2}"
+   ],
+   "float_object": {
+    "pi": 3.14159,
+    "euler": 2.71828,
+    "sqrt2": 1.41421,
+    "scientific": "${-123e+2}"
+   }
+  }
+ ]
+}

test/helpers/terraform-config/test_floats.tf

@@ -0,0 +1,20 @@
+locals {
+  simple_float = 123.456
+  small_float = 0.123
+  large_float = 9876543.21
+  negative_float = -42.5
+  negative_small = -0.001
+  scientific_positive = 1.23e5
+  scientific_negative = 9.87e-3
+  scientific_large = 6.022e+23
+  integer_as_float = 100.0
+  float_calculation = 105e+2 * 3.0 / 2.1
+  float_comparison = 5e1 > 2.3 ? 1.0 : 0.0
+  float_list = [1.1, 2.2, 3.3, -4.4, 5.5e2]
+  float_object = {
+    pi = 3.14159
+    euler = 2.71828
+    sqrt2 = 1.41421
+    scientific = -123e+2
+  }
+}

test/unit/test_hcl2_syntax.py

@@ -156,12 +156,12 @@ def test_index(self):
 
     def test_e_notation(self):
         literals = {
-            "var = 3e4": {"var": 30000.0},
-            "var = 3.5e5": {"var": 350000.0},
-            "var = -3e6": {"var": -3e6},
-            "var = -2.3e4": {"var": -2.3e4},
-            "var = -5e-2": {"var": -5e-2},
-            "var = -6.1e-3": {"var": -6.1e-3},
+            "var = 3e4": {"var": "${3e4}"},
+            "var = 3.5e5": {"var": "${3.5e5}"},
+            "var = -3e6": {"var": "${-3e6}"},
+            "var = -2.3e4": {"var": "${-2.3e4}"},
+            "var = -5e-2": {"var": "${-5e-2}"},
+            "var = -6.1e-3": {"var": "${-6.1e-3}"},
         }
         for actual, expected in literals.items():
             result = self.load_to_dict(actual)