# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1458343076 25200
# Node ID cdbc253066965347205f7d9b94e334d775495036
# Parent  3c8f0a60550466c17cc1993ead24328314a232b4
run-tests: add --with-python3 to define a Python 3 interpreter

Currently, very few parts of Mercurial run under Python 3, notably the
test harness.

We want to write tests that run Python 3. For example, we want to
extend test-check-py3-compat.t to parse and load Python files.
However, we have a problem: finding appropriate files requires
running `hg files` and this requires Python 2 until `hg` works
with Python 3.

As a temporary workaround, we add --with-python3 to the test harness
to allow us to define the path to a Python 3 interpreter. This
interpreter is made available to the test environment via $PYTHON3 so
tests can run things with Python 3 while the test harness and `hg`
invocations continue to run from Python 2. To round out the feature,
a "py3exe" hghave check has been added.

diff -r 3c8f0a605504 -r cdbc25306696 tests/hghave.py
--- a/tests/hghave.py	Fri Mar 18 11:06:03 2016 -0700
+++ b/tests/hghave.py	Fri Mar 18 16:17:56 2016 -0700
@@ -443,6 +443,10 @@
 def has_py3k():
     return 3 == sys.version_info[0]
 
+@check("py3exe", "a Python 3.x interpreter is available")
+def has_python3exe():
+    return 'PYTHON3' in os.environ
+
 @check("pure", "running with pure Python code")
 def has_pure():
     return any([
diff -r 3c8f0a605504 -r cdbc25306696 tests/run-tests.py
--- a/tests/run-tests.py	Fri Mar 18 11:06:03 2016 -0700
+++ b/tests/run-tests.py	Fri Mar 18 16:17:56 2016 -0700
@@ -255,6 +255,11 @@
                       help="use specified chg wrapper in place of hg")
     parser.add_option("-3", "--py3k-warnings", action="store_true",
         help="enable Py3k warnings on Python 2.6+")
+    # This option should be deleted once test-check-py3-compat.t and other
+    # Python 3 tests run with Python 3.
+    parser.add_option("--with-python3", metavar="PYTHON3",
+                      help="Python 3 interpreter (if running under Python 2)"
+                           " (TEMPORARY)")
     parser.add_option('--extra-config-opt', action="append",
                       help='set the given config opt in the test hgrc')
     parser.add_option('--random', action="store_true",
@@ -353,6 +358,27 @@
         if PYTHON3:
             parser.error(
                 '--py3k-warnings can only be used on Python 2.6 and 2.7')
+    if options.with_python3:
+        if PYTHON3:
+            parser.error('--with-python3 cannot be used when executing with '
+                         'Python 3')
+
+        # Verify Python3 executable is acceptable.
+        proc = subprocess.Popen([options.with_python3, b'--version'],
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.STDOUT)
+        out, _err = proc.communicate()
+        ret = proc.wait()
+        if ret != 0:
+            parser.error('could not determine version of python 3')
+        if not out.startswith('Python '):
+            parser.error('unexpected output from python3 --version: %s' %
+                         out)
+        vers = version.LooseVersion(out[len('Python '):])
+        if vers < version.LooseVersion('3.5.0'):
+            parser.error('--with-python3 version must be 3.5.0 or greater; '
+                         'got %s' % out)
+
     if options.blacklist:
         options.blacklist = parselistfiles(options.blacklist, 'blacklist')
     if options.whitelist:
@@ -1987,6 +2013,9 @@
         osenvironb[b"BINDIR"] = self._bindir
         osenvironb[b"PYTHON"] = PYTHON
 
+        if self.options.with_python3:
+            osenvironb[b'PYTHON3'] = self.options.with_python3
+
         fileb = _bytespath(__file__)
         runtestdir = os.path.abspath(os.path.dirname(fileb))
         osenvironb[b'RUNTESTDIR'] = runtestdir