Use a HOSTNAME environment variable instead of socket.getfqdn() in Re…

…sultLog (#1616)

This makes it possible to prevent an undesired DNS query.

Fixes #1615

docs/changelog/1615.feature.rst

@@ -0,0 +1,3 @@
+The ``ResultLog`` now prefers ``HOSTNAME`` environment variable value (if set) over the full qualified domain name of localhost.
+This makes it possible to disable an undesired DNS lookup,
+which happened on all ``tox`` invocations, including trivial ones - by :user:`hroncok`

src/tox/logs/result.py

@@ -2,6 +2,7 @@
 from __future__ import absolute_import, unicode_literals
 
 import json
+import os
 import socket
 import sys
 
@@ -21,7 +22,7 @@ def __init__(self):
             "reportversion": "1",
             "toxversion": __version__,
             "platform": sys.platform,
-            "host": socket.getfqdn(),
+            "host": os.getenv(str("HOSTNAME")) or socket.getfqdn(),
             "commands": command_log,
         }
 

tests/unit/test_result.py

@@ -17,7 +17,23 @@ def create_fake_pkg(tmpdir):
     return pkg
 
 
-def test_pre_set_header():
+@pytest.fixture()
+def no_hostname_envvar():
+    hostname = os.getenv("HOSTNAME")
+    if hostname:
+        del os.environ["HOSTNAME"]
+    try:
+        yield
+    finally:
+        try:
+            del os.environ["HOSTNAME"]
+        except KeyError:
+            pass
+        if hostname:
+            os.environ["HOSTNAME"] = hostname
+
+
+def test_pre_set_header(no_hostname_envvar):
     replog = ResultLog()
     d = replog.dict
     assert replog.dict == d
@@ -30,7 +46,7 @@ def test_pre_set_header():
     assert replog2.dict == replog.dict
 
 
-def test_set_header(pkg):
+def test_set_header(pkg, no_hostname_envvar):
     replog = ResultLog()
     d = replog.dict
     assert replog.dict == d
@@ -48,6 +64,12 @@ def test_set_header(pkg):
     assert replog2.dict == replog.dict
 
 
+def test_hosname_via_envvar(no_hostname_envvar):
+    os.environ["HOSTNAME"] = "toxicity"
+    replog = ResultLog()
+    assert replog.dict["host"] == "toxicity"
+
+
 def test_addenv_setpython(pkg):
     replog = ResultLog()
     envlog = replog.get_envlog("py36")