introduce --assertmode option

_pytest/assertion/__init__.py

@@ -6,6 +6,7 @@ import imp
 import marshal
 import struct
 import sys
+import pytest
 from _pytest.monkeypatch import monkeypatch
 from _pytest.assertion import reinterpret, util
 
@@ -18,26 +19,40 @@ else:
 
 def pytest_addoption(parser):
     group = parser.getgroup("debugconfig")
+    group._addoption('--assertmode', action="store", dest="assertmode",
+                     choices=("on", "old", "off", "default"), default="default",
+                     metavar="on|old|off",
+                     help="Control assertion debugging tools")
     group._addoption('--no-assert', action="store_true", default=False,
-        dest="noassert",
+        dest="noassert", help="DEPRECATED equivalent to --assertmode=off")
-        help="disable python assert expression reinterpretation."),
+    group._addoption('--nomagic', action="store_true", default=False,
+                     dest="nomagic",
+                     help="DEPRECATED equivalent to --assertmode=off")
+
 
 def pytest_configure(config):
     global rewrite_asserts
-    m = monkeypatch()
-    config._cleanup.append(m.undo)
     warn_about_missing_assertion()
-    if not config.getvalue("noassert") and not config.getvalue("nomagic"):
+    mode = config.getvalue("assertmode")
+    if config.getvalue("noassert") or config.getvalue("nomagic"):
+        if mode not in ("off", "default"):
+            raise pytest.UsageError("assertion options conflict")
+        mode = "off"
+    elif mode == "default":
+        mode = "on"
+    if mode != "off":
         def callbinrepr(op, left, right):
             hook_result = config.hook.pytest_assertrepr_compare(
                 config=config, op=op, left=left, right=right)
             for new_expl in hook_result:
                 if new_expl:
                     return '\n~'.join(new_expl)
+        m = monkeypatch()
+        config._cleanup.append(m.undo)
         m.setattr(py.builtin.builtins, 'AssertionError',
                   reinterpret.AssertionError)
         m.setattr(util, '_reprcompare', callbinrepr)
-    else:
+    if mode != "on":
         rewrite_asserts = None
 
 def _write_pyc(co, source_path):

_pytest/helpconfig.py

@@ -16,9 +16,6 @@ def pytest_addoption(parser):
     group.addoption('--traceconfig',
                action="store_true", dest="traceconfig", default=False,
                help="trace considerations of conftest.py files."),
-    group._addoption('--nomagic',
-               action="store_true", dest="nomagic", default=False,
-               help="don't reinterpret asserts, no traceback cutting. ")
     group.addoption('--debug',
                action="store_true", dest="debug", default=False,
                help="generate and show internal debugging information.")

testing/test_assertion.py

@@ -160,7 +160,7 @@ def test_sequence_comparison_uses_repr(testdir):
     ])
 
 
-def test_functional(testdir):
+def test_assertion_options(testdir):
     testdir.makepyfile("""
         def test_hello():
             x = 3
@@ -168,8 +168,30 @@ def test_functional(testdir):
     """)
     result = testdir.runpytest()
     assert "3 == 4" in result.stdout.str()
-    result = testdir.runpytest("--no-assert")
+    off_options = (("--no-assert",),
+                   ("--nomagic",),
+                   ("--no-assert", "--nomagic"),
+                   ("--assertmode=off",),
+                   ("--assertmode=off", "--no-assert"),
+                   ("--assertmode=off", "--nomagic"),
+                   ("--assertmode=off," "--no-assert", "--nomagic"))
+    for opt in off_options:
+        result = testdir.runpytest(*opt)
         assert "3 == 4" not in result.stdout.str()
+    for mode in "on", "old":
+        for other_opt in off_options[:3]:
+            opt = ("--assertmode=" + mode,) + other_opt
+            result = testdir.runpytest(*opt)
+            assert result.ret == 3
+            assert "assertion options conflict" in result.stderr.str()
+
+def test_old_assert_mode(testdir):
+    testdir.makepyfile("""
+        def test_in_old_mode():
+            assert "@py_builtins" not in globals()
+    """)
+    result = testdir.runpytest("--assertmode=old")
+    assert result.ret == 0
 
 def test_triple_quoted_string_issue113(testdir):
     testdir.makepyfile("""