Show traceback during collection

CHANGELOG.rst

@@ -3,13 +3,20 @@
 
 *
 
-*
+* Import errors when collecting test modules now display the full traceback (`#1976`_).
+  Thanks `@cwitty`_ for the report and `@nicoddemus`_ for the PR.
 
 *
 
 *
 
 
+.. _@cwitty: https://github.com/cwitty
+
+.. _#1976: https://github.com/pytest-dev/pytest/issues/1976
+
+
+
 3.0.3
 =====
 

_pytest/python.py

@@ -22,11 +22,16 @@
     getlocation, enum,
 )
 
-cutdir2 = py.path.local(_pytest.__file__).dirpath()
 cutdir1 = py.path.local(pluggy.__file__.rstrip("oc"))
+cutdir2 = py.path.local(_pytest.__file__).dirpath()
+cutdir3 = py.path.local(py.__file__).dirpath()
 
 
 def filter_traceback(entry):
+    """Return True if a TracebackEntry instance should be removed from tracebacks:
+    * dynamically generated code (no code to show up for it);
+    * internal traceback from pytest or its internal libraries, py and pluggy.
+    """
     # entry.path might sometimes return a str object when the entry
     # points to dynamically generated code
     # see https://bitbucket.org/pytest-dev/py/issues/71
@@ -37,7 +42,7 @@ def filter_traceback(entry):
     # entry.path might point to an inexisting file, in which case it will
     # alsso return a str object. see #1133
     p = py.path.local(entry.path)
-    return p != cutdir1 and not p.relto(cutdir2)
+    return p != cutdir1 and not p.relto(cutdir2) and not p.relto(cutdir3)
 
 
 
@@ -424,12 +429,17 @@ def _importtestmodule(self):
                  % e.args
             )
         except ImportError:
-            exc_class, exc, _ = sys.exc_info()
+            from _pytest._code.code import ExceptionInfo
+            exc_info = ExceptionInfo()
+            if self.config.getoption('verbose') < 2:
+                exc_info.traceback = exc_info.traceback.filter(filter_traceback)
+            exc_repr = exc_info.getrepr(style='short') if exc_info.traceback else exc_info.exconly()
+            formatted_tb = py._builtin._totext(exc_repr)
             raise self.CollectError(
-                "ImportError while importing test module '%s'.\n"
-                "Original error message:\n'%s'\n"
-                "Make sure your test modules/packages have valid Python names."
-                % (self.fspath, exc or exc_class)
+                "ImportError while importing test module '{fspath}'.\n"
+                "Hint: make sure your test modules/packages have valid Python names.\n"
+                "Traceback:\n"
+                "{traceback}".format(fspath=self.fspath, traceback=formatted_tb)
             )
         except _pytest.runner.Skipped as e:
             if e.allow_module_level:

testing/acceptance_test.py

@@ -120,7 +120,7 @@ def test_this():
         result.stdout.fnmatch_lines([
             #XXX on jython this fails:  ">   import import_fails",
             "ImportError while importing test module*",
-            "'No module named *does_not_work*",
+            "*No module named *does_not_work*",
         ])
         assert result.ret == 2
 

testing/python/collect.py

@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import os
 import sys
 from textwrap import dedent
 
@@ -68,9 +69,41 @@ def test_invalid_test_module_name(self, testdir):
         result = testdir.runpytest("-rw")
         result.stdout.fnmatch_lines([
             "ImportError while importing test module*test_one.part1*",
-            "Make sure your test modules/packages have valid Python names.",
+            "Hint: make sure your test modules/packages have valid Python names.",
         ])
 
+    @pytest.mark.parametrize('verbose', [0, 1, 2])
+    def test_show_traceback_import_error(self, testdir, verbose):
+        """Import errors when collecting modules should display the traceback (#1976).
+
+        With low verbosity we omit pytest and internal modules, otherwise show all traceback entries.
+        """
+        testdir.makepyfile(
+            foo_traceback_import_error="""
+               from bar_traceback_import_error import NOT_AVAILABLE
+           """,
+            bar_traceback_import_error="",
+        )
+        testdir.makepyfile("""
+               import foo_traceback_import_error
+        """)
+        args = ('-v',) * verbose
+        result = testdir.runpytest(*args)
+        result.stdout.fnmatch_lines([
+            "ImportError while importing test module*",
+            "Traceback:",
+            "*from bar_traceback_import_error import NOT_AVAILABLE",
+            "*cannot import name *NOT_AVAILABLE*",
+        ])
+        assert result.ret == 2
+
+        stdout = result.stdout.str()
+        for name in ('_pytest', os.path.join('py', '_path')):
+            if verbose == 2:
+                assert name in stdout
+            else:
+                assert name not in stdout
+
 
 class TestClass:
     def test_class_with_init_warning(self, testdir):

testing/test_collection.py

@@ -172,17 +172,6 @@ def pytest_collect_directory(self, path, parent):
         assert "world" in wascalled
 
 class TestPrunetraceback:
-    def test_collection_error(self, testdir):
-        p = testdir.makepyfile("""
-            import not_exists
-        """)
-        result = testdir.runpytest(p)
-        assert "__import__" not in result.stdout.str(), "too long traceback"
-        result.stdout.fnmatch_lines([
-            "*ERROR collecting*",
-            "ImportError while importing test module*",
-            "'No module named *not_exists*",
-        ])
 
     def test_custom_repr_failure(self, testdir):
         p = testdir.makepyfile("""

testing/test_terminal.py

@@ -667,7 +667,7 @@ def test_collect_fail(self, testdir, option):
         result = testdir.runpytest(*option.args)
         result.stdout.fnmatch_lines([
             "ImportError while importing*",
-            "'No module named *xyz*",
+            "*No module named *xyz*",
             "*1 error*",
         ])