Avoid floating point inaccuracies

Author: lognaturel

pyxform/errors.py

@@ -423,8 +423,8 @@ class ErrorCode(Enum):
         name="Range type - parameter outside range",
         msg=(
             "[row : {row}] On the 'survey' sheet, the 'parameters' value is invalid. "
-            "For the 'range' question type, the parameter '{name}' must be a within "
-            "the range (between the 'start' and 'end' values, inclusive)."
+            "For the 'range' question type, the parameter '{name}' must be "
+            "between the 'start' and 'end' values, inclusive)."
         ),
     )
     RANGE_006 = Detail(

pyxform/validators/pyxform/question_types.py

@@ -3,6 +3,7 @@
 """
 
 from collections.abc import Collection, Iterable
+from decimal import Decimal, InvalidOperation
 from math import isinf
 from typing import Any
 
@@ -138,14 +139,14 @@ def process_range_question_type(
         if key not in parameters:
             parameters[key] = defaults[key]
 
-    def process_parameter(name: str) -> float | None:
+    def process_parameter(name: str) -> Decimal | None:
         value = parameters.get(name)
         if value is None:
             return value
         err = False
         try:
-            value = float(value)
-        except ValueError:
+            value = Decimal(value)
+        except InvalidOperation:
             err = True
 
         if err or isinf(value):
@@ -202,8 +203,8 @@ def process_parameter(name: str) -> float | None:
         for label in tick_list:
             errored = False
             try:
-                label = float(label.get("name"))
-            except ValueError:
+                label = Decimal(label.get("name"))
+            except InvalidOperation:
                 errored = True
 
             if errored or isinf(label):
@@ -230,9 +231,9 @@ def process_parameter(name: str) -> float | None:
 
         parameters["odk:tick-labelset"] = parameters.pop("tick_labelset")
 
-    # Default is integer, but if the floats have decimals then change the bind type.
+    # Default is integer, but if the values have decimals then change the bind type.
     if any(
-        i is not None and not i.is_integer()
+        i is not None and not i == i.to_integral_value()
         for i in (start, end, step, tick_interval, placeholder)
     ):
         row["bind"] = row.get("bind", {})

tests/test_range.py

@@ -294,40 +294,83 @@ def test_parameter_greater_than_range__ok(self):
                         ],
                     )
 
-    def test_parameter_not_a_multiple_of_step__error(self):
+    def test_tick_interval_not_a_multiple_of_step__error(self):
         """Should raise an error if the relevant ticks parameter is not a multiple of 'step'."""
         # RI003 RP001
         md = """
         | survey |
+        | | type  | name | label | parameters                                  |
+        | | range | q1   | Q1    | start=-3 end=3 step=2 tick_interval={value} |
+        """
+        cases = ("-3", "3", "-1", "1")
+        for value in cases:
+            with self.subTest(("tick_interval", value)):
+                self.assertPyxformXform(
+                    md=md.format(name="tick_interval", value=value),
+                    errored=True,
+                    error__contains=[
+                        ErrorCode.RANGE_004.value.format(row=2, name="tick_interval")
+                    ],
+                )
+
+    def test_tick_interval_not_a_multiple_of_step__error(self):
+        """Should raise an error if the placeholder is not a multiple of 'step' starting at 'start'."""
+        # RI003 RP001
+        md = """
+        | survey |
+        | | type  | name | label | parameters                                  |
+        | | range | q1   | Q1    | start=-3 end=3 step=2 placeholder={value} |
+        """
+        cases = ("-2", "2", "0")
+        for value in cases:
+            with self.subTest(("placeholder", value)):
+                self.assertPyxformXform(
+                    md=md.format(name="placeholder", value=value),
+                    errored=True,
+                    error__contains=[
+                        ErrorCode.RANGE_004.value.format(row=2, name="placeholder")
+                    ],
+                )
+
+    def test_parameter_not_a_multiple_of_step__ok(self):
+        """Should not raise an error if the relevant ticks parameter is a multiple of 'step'."""
+        # RI003 RP001
+        md = """
+        | survey |
         | | type  | name | label | parameters                           |
-        | | range | q1   | Q1    | start=-3 end=3 step=2 {name}={value} |
+        | | range | q1   | Q1    | start=-1 end=1 step=1 {name}={value} |
         """
-        params = ("tick_interval", "placeholder")
-        cases = ("3", "-3")
-        for name in params:
+        params = (
+            ("tick_interval", "odk:tick-interval"),
+            ("placeholder", "odk:placeholder"),
+        )
+        cases = ("1", "-1")
+        for name, attr in params:
             for value in cases:
-                with self.subTest((name, value)):
+                with self.subTest((name, attr, value)):
                     self.assertPyxformXform(
                         md=md.format(name=name, value=value),
-                        errored=True,
-                        error__contains=[
-                            ErrorCode.RANGE_004.value.format(row=2, name=name)
+                        xml__xpath_match=[
+                            xpq.body_range(
+                                "q1",
+                                {"start": "-1", "end": "1", "step": "1", attr: value},
+                            ),
                         ],
                     )
 
-    def test_parameter_not_a_multiple_of_step__ok(self):
+    def test_parameter_not_a_multiple_of_step_decimal__ok(self):
         """Should not raise an error if the relevant ticks parameter is a multiple of 'step'."""
         # RI003 RP001
         md = """
         | survey |
         | | type  | name | label | parameters                           |
-        | | range | q1   | Q1    | start=-1 end=1 step=1 {name}={value} |
+        | | range | q1   | Q1    | start=-1 end=1 step=0.1 {name}={value} |
         """
         params = (
             ("tick_interval", "odk:tick-interval"),
             ("placeholder", "odk:placeholder"),
         )
-        cases = ("1", "-1")
+        cases = ("0.6", "-0.6")
         for name, attr in params:
             for value in cases:
                 with self.subTest((name, attr, value)):
@@ -336,7 +379,7 @@ def test_parameter_not_a_multiple_of_step__ok(self):
                         xml__xpath_match=[
                             xpq.body_range(
                                 "q1",
-                                {"start": "-1", "end": "1", "step": "1", attr: value},
+                                {"start": "-1", "end": "1", "step": "0.1", attr: value},
                             ),
                         ],
                     )
@@ -349,7 +392,7 @@ def test_placeholder_outside_range__error(self):
         | | type  | name | label | parameters                               |
         | | range | q1   | Q1    | start=3 end=7 step=2 placeholder={value} |
         """
-        cases = ("2", "8")
+        cases = ("1", "9")
         for value in cases:
             with self.subTest(value):
                 self.assertPyxformXform(
@@ -368,7 +411,7 @@ def test_placeholder_outside_inverted_range__error(self):
         | | type  | name | label | parameters                               |
         | | range | q1   | Q1    | start=7 end=3 step=2 placeholder={value} |
         """
-        cases = ("8", "1")
+        cases = ("9", "1")
         for value in cases:
             with self.subTest(value):
                 self.assertPyxformXform(