fix pytest-dev#5686, mktemp now fails given absolute and non-normaliz…

…ed paths.

changelog/5686.feature.rst

@@ -0,0 +1 @@
+tmpdir_factory.mktemp now fails given absolute and non-normalized paths.

src/_pytest/tmpdir.py

@@ -15,6 +15,7 @@
 from .pathlib import Path
 from _pytest.fixtures import FixtureRequest
 from _pytest.monkeypatch import MonkeyPatch
+from _pytest.outcomes import fail
 
 
 @attr.s
@@ -47,6 +48,9 @@ def from_config(cls, config) -> "TempPathFactory":
 
     def mktemp(self, basename: str, numbered: bool = True) -> Path:
         """makes a temporary directory managed by the factory"""
+
+        if os.path.isabs(basename):
+            fail("Absolute and non-normalized path is disallowed: {}".format(basename))
         if not numbered:
             p = self.getbasetemp().joinpath(basename)
             p.mkdir()

testing/test_tmpdir.py

@@ -81,14 +81,33 @@ def test_basetemp(testdir):
         import pytest
         def test_1(tmpdir_factory):
             tmpdir_factory.mktemp('hello', numbered=False)
-    """
+        """
     )
+
     result = testdir.runpytest(p, "--basetemp=%s" % mytemp)
     assert result.ret == 0
     print(mytemp)
     assert mytemp.join("hello").check()
 
 
+def test_basetemp_with_abs_path(testdir):
+    mytemp = testdir.tmpdir.mkdir("mytemp")
+    abs_path = "/hello"
+    p = testdir.makepyfile(
+        """
+        import pytest
+        def test_abs_path(tmpdir_factory):
+            tmpdir_factory.mktemp('{}', numbered=False)
+        """.format(
+            abs_path
+        )
+    )
+
+    result = testdir.runpytest(p, "--basetemp=%s" % mytemp)
+    assert result.ret == 1
+    result.stdout.fnmatch_lines("*path is disallowed: {}*".format(abs_path))
+
+
 def test_tmpdir_always_is_realpath(testdir):
     # the reason why tmpdir should be a realpath is that
     # when you cd to it and do "os.getcwd()" you will anyway