From af9f27a874be2a86621a58a5de6c7cecbbb67168 Mon Sep 17 00:00:00 2001
From: Pierre Mourlanne <pmourlanne@gmail.com>
Date: Sat, 13 Mar 2021 15:01:23 +0100
Subject: [PATCH] Approx decimal sequence mapping (#8422)

---
 changelog/8421.feature.rst |  1 +
 src/_pytest/python_api.py  |  2 ++
 testing/python/approx.py   | 14 ++++++++++++++
 3 files changed, 17 insertions(+)
 create mode 100644 changelog/8421.feature.rst

diff --git a/changelog/8421.feature.rst b/changelog/8421.feature.rst
new file mode 100644
index 000000000..c729ca395
--- /dev/null
+++ b/changelog/8421.feature.rst
@@ -0,0 +1 @@
+:func:`pytest.approx` now works on :class:`~decimal.Decimal` within mappings/dicts and sequences/lists.
diff --git a/src/_pytest/python_api.py b/src/_pytest/python_api.py
index 7e0c86479..2285e22a3 100644
--- a/src/_pytest/python_api.py
+++ b/src/_pytest/python_api.py
@@ -72,6 +72,8 @@ class ApproxBase:
         return not (actual == self)
 
     def _approx_scalar(self, x) -> "ApproxScalar":
+        if isinstance(x, Decimal):
+            return ApproxDecimal(x, rel=self.rel, abs=self.abs, nan_ok=self.nan_ok)
         return ApproxScalar(x, rel=self.rel, abs=self.abs, nan_ok=self.nan_ok)
 
     def _yield_comparisons(self, actual):
diff --git a/testing/python/approx.py b/testing/python/approx.py
index db6124e39..a0a914842 100644
--- a/testing/python/approx.py
+++ b/testing/python/approx.py
@@ -313,6 +313,12 @@ class TestApprox:
         assert approx(expected, rel=5e-7, abs=0) == actual
         assert approx(expected, rel=5e-8, abs=0) != actual
 
+    def test_list_decimal(self):
+        actual = [Decimal("1.000001"), Decimal("2.000001")]
+        expected = [Decimal("1"), Decimal("2")]
+
+        assert actual == approx(expected)
+
     def test_list_wrong_len(self):
         assert [1, 2] != approx([1])
         assert [1, 2] != approx([1, 2, 3])
@@ -346,6 +352,14 @@ class TestApprox:
         assert approx(expected, rel=5e-7, abs=0) == actual
         assert approx(expected, rel=5e-8, abs=0) != actual
 
+    def test_dict_decimal(self):
+        actual = {"a": Decimal("1.000001"), "b": Decimal("2.000001")}
+        # Dictionaries became ordered in python3.6, so switch up the order here
+        # to make sure it doesn't matter.
+        expected = {"b": Decimal("2"), "a": Decimal("1")}
+
+        assert actual == approx(expected)
+
     def test_dict_wrong_len(self):
         assert {"a": 1, "b": 2} != approx({"a": 1})
         assert {"a": 1, "b": 2} != approx({"a": 1, "c": 2})