From b9fe3a49b7fc1a77995b41fda3a5243d3f78e1d9 Mon Sep 17 00:00:00 2001
From: Gaurav Kumar Biswas <2025sl93041@wilp.bits-pilani.ac.in>
Date: Tue, 27 Oct 2026 22:09:29 +0530
Subject: [PATCH] fix: raise NumberFormatError for invalid string in
 NumberPattern.apply

Wrap `decimal.Decimal(str(value))` in `NumberPattern.apply()` and
`_get_compact_format()` in a try/except to catch
`decimal.InvalidOperation` and re-raise as `NumberFormatError`.

Previously, passing an invalid string like `"not_a_number"` to any
formatting function (format_decimal, format_currency, format_percent,
format_compact_decimal) would propagate a raw
`decimal.InvalidOperation` exception. The public API contract
documents `NumberFormatError` as the error type for bad input; all
other invalid-value paths already raise it.

Closes #702
---
 CHANGES.rst           |  9 +++++++++
 babel/numbers.py      | 10 ++++++++--
 tests/test_numbers.py |  7 +++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index b09e184e8..4f1d71bc2 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,15 @@
 Babel Changelog
 ===============
 
+Version 2.19.0 (Unreleased)
+----------------------------
+
+Bugfixes
+~~~~~~~~
+
+* Numbers: Raise ``NumberFormatError`` instead of ``decimal.InvalidOperation``
+  when formatting an invalid string value by @2025sl93041-gkb in :gh:`702`
+
 Version 2.18.0
 --------------
 
diff --git a/babel/numbers.py b/babel/numbers.py
index b782521e5..4669db167 100644
--- a/babel/numbers.py
+++ b/babel/numbers.py
@@ -664,7 +664,10 @@ def _get_compact_format(
     https://www.unicode.org/reports/tr35/tr35-45/tr35-numbers.html#Compact_Number_Formats.
     """
     if not isinstance(number, decimal.Decimal):
-        number = decimal.Decimal(str(number))
+        try:
+            number = decimal.Decimal(str(number))
+        except decimal.InvalidOperation as e:
+            raise NumberFormatError(f"{number!r} is not a valid number") from e
     if number.is_nan() or number.is_infinite():
         return number, None
     format = None
@@ -1477,7 +1480,10 @@ def apply(
         :raise UnsupportedNumberingSystemError: If the numbering system is not supported by the locale.
         """
         if not isinstance(value, decimal.Decimal):
-            value = decimal.Decimal(str(value))
+            try:
+                value = decimal.Decimal(str(value))
+            except decimal.InvalidOperation as e:
+                raise NumberFormatError(f"{value!r} is not a valid number") from e
 
         value = value.scaleb(self.scale)
 
diff --git a/tests/test_numbers.py b/tests/test_numbers.py
index d20a18315..551b7df4a 100644
--- a/tests/test_numbers.py
+++ b/tests/test_numbers.py
@@ -695,3 +695,10 @@ def test_issue_1076_fixes():
     assert numbers.format_compact_decimal(2345678, format_type="long", locale="ja") == "235万"
     # Swahili does not define an accounting currency format; root aliases it to the standard format.
     assert numbers.format_currency(-2, "USD", format_type="accounting", locale="sw") == "-US$\xa02.00"
+
+
+def test_number_pattern_apply_invalid_string_raises_number_format_error():
+    from unittest.mock import MagicMock
+    pattern = numbers.parse_pattern('0.###')
+    with pytest.raises(numbers.NumberFormatError, match="is not a valid number"):
+        pattern.apply('not_a_number', locale=MagicMock())