From 9543d1901f3704432ff2f7a21d4a17fe9cf6cb2c Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Tue, 22 Jan 2019 19:42:22 -0200
Subject: [PATCH] Group warnings by message instead of by test id

---
 changelog/4402.bugfix.rst                     |  4 ++
 src/_pytest/terminal.py                       | 42 +++++++++----------
 .../test_group_warnings_by_message.py         | 16 +++++++
 testing/test_warnings.py                      | 19 +++++++++
 4 files changed, 60 insertions(+), 21 deletions(-)
 create mode 100644 changelog/4402.bugfix.rst
 create mode 100644 testing/example_scripts/warnings/test_group_warnings_by_message.py

diff --git a/changelog/4402.bugfix.rst b/changelog/4402.bugfix.rst
new file mode 100644
index 000000000..9b338aaa5
--- /dev/null
+++ b/changelog/4402.bugfix.rst
@@ -0,0 +1,4 @@
+Warning summary now groups warnings by message instead of by test id.
+
+This makes the output more compact and better conveys the general idea of how much code is
+actually generating warnings, instead of how many tests call that code.
diff --git a/src/_pytest/terminal.py b/src/_pytest/terminal.py
index bea02306b..2a3d71a69 100644
--- a/src/_pytest/terminal.py
+++ b/src/_pytest/terminal.py
@@ -7,7 +7,7 @@ from __future__ import division
 from __future__ import print_function
 
 import argparse
-import itertools
+import collections
 import platform
 import sys
 import time
@@ -724,33 +724,33 @@ class TerminalReporter(object):
 
             final = hasattr(self, "_already_displayed_warnings")
             if final:
-                warnings = all_warnings[self._already_displayed_warnings :]
+                warning_reports = all_warnings[self._already_displayed_warnings :]
             else:
-                warnings = all_warnings
-            self._already_displayed_warnings = len(warnings)
-            if not warnings:
+                warning_reports = all_warnings
+            self._already_displayed_warnings = len(warning_reports)
+            if not warning_reports:
                 return
 
-            grouped = itertools.groupby(
-                warnings, key=lambda wr: wr.get_location(self.config)
-            )
+            reports_grouped_by_message = collections.OrderedDict()
+            for wr in warning_reports:
+                reports_grouped_by_message.setdefault(wr.message, []).append(wr)
 
             title = "warnings summary (final)" if final else "warnings summary"
             self.write_sep("=", title, yellow=True, bold=False)
-            for location, warning_records in grouped:
-                # legacy warnings show their location explicitly, while standard warnings look better without
-                # it because the location is already formatted into the message
-                warning_records = list(warning_records)
-                if location:
-                    self._tw.line(str(location))
-                for w in warning_records:
+            for message, warning_reports in reports_grouped_by_message.items():
+                has_any_location = False
+                for w in warning_reports:
+                    location = w.get_location(self.config)
                     if location:
-                        lines = w.message.splitlines()
-                        indented = "\n".join("  " + x for x in lines)
-                        message = indented.rstrip()
-                    else:
-                        message = w.message.rstrip()
-                    self._tw.line(message)
+                        self._tw.line(str(location))
+                        has_any_location = True
+                if has_any_location:
+                    lines = message.splitlines()
+                    indented = "\n".join("  " + x for x in lines)
+                    message = indented.rstrip()
+                else:
+                    message = message.rstrip()
+                self._tw.line(message)
                 self._tw.line()
             self._tw.line("-- Docs: https://docs.pytest.org/en/latest/warnings.html")
 
diff --git a/testing/example_scripts/warnings/test_group_warnings_by_message.py b/testing/example_scripts/warnings/test_group_warnings_by_message.py
new file mode 100644
index 000000000..c736135b7
--- /dev/null
+++ b/testing/example_scripts/warnings/test_group_warnings_by_message.py
@@ -0,0 +1,16 @@
+import warnings
+
+import pytest
+
+
+def func():
+    warnings.warn(UserWarning("foo"))
+
+
+@pytest.mark.parametrize("i", range(5))
+def test_foo(i):
+    func()
+
+
+def test_bar():
+    func()
diff --git a/testing/test_warnings.py b/testing/test_warnings.py
index e8075b617..984aae027 100644
--- a/testing/test_warnings.py
+++ b/testing/test_warnings.py
@@ -693,3 +693,22 @@ def test_warnings_checker_twice():
         warnings.warn("Message A", UserWarning)
     with expectation:
         warnings.warn("Message B", UserWarning)
+
+
+@pytest.mark.filterwarnings("always")
+def test_group_warnings_by_message(testdir):
+    testdir.copy_example("warnings/test_group_warnings_by_message.py")
+    result = testdir.runpytest()
+    result.stdout.fnmatch_lines(
+        [
+            "test_group_warnings_by_message.py::test_foo[0]",
+            "test_group_warnings_by_message.py::test_foo[1]",
+            "test_group_warnings_by_message.py::test_foo[2]",
+            "test_group_warnings_by_message.py::test_foo[3]",
+            "test_group_warnings_by_message.py::test_foo[4]",
+            "test_group_warnings_by_message.py::test_bar",
+        ]
+    )
+    warning_code = 'warnings.warn(UserWarning("foo"))'
+    assert warning_code in result.stdout.str()
+    assert result.stdout.str().count(warning_code) == 1