Revendor editor and make dateutil optional

Re-implemented the ``python-editor`` dependency as a small internal
function to avoid the need for external dependencies.
The implementation is based on the original
version in 7b91b325ff43a0e9235e0f15b57391fa92352626.

Make the ``python-dateutil`` library an optional dependency.
This library is only required if the ``timezone`` option
is used in the Alembic configuration.
An extra require named ``tz`` is available with
``pip install alembic[tz]`` to install it.

Fixes: #674
Fixes: #856
Change-Id: I07f17b2fea01e3a3d677ce95333fe3e8d8d438fd

3 files changed, 125 insertions, 17 deletions

diff --git a/tests/test_command.py b/tests/test_command.py
index 4114be0..a477a1d 100644
--- a/tests/test_command.py
+++ b/tests/test_command.py
@@ -11,12 +11,10 @@ from sqlalchemy import text
 from alembic import __version__
 from alembic import command
 from alembic import config
-from alembic import testing
 from alembic import util
 from alembic.script import ScriptDirectory
 from alembic.testing import assert_raises
 from alembic.testing import assert_raises_message
-from alembic.testing import config as testing_config
 from alembic.testing import eq_
 from alembic.testing import is_false
 from alembic.testing import is_true
@@ -924,7 +922,7 @@ class EditTest(TestBase):
             % (EditTest.cfg.config_args["here"], EditTest.c)
         )
 
-        with mock.patch("alembic.util.edit") as edit:
+        with mock.patch("alembic.util.open_in_editor") as edit:
             command.edit(self.cfg, "head")
             edit.assert_called_with(expected_call_arg)
 
@@ -934,22 +932,10 @@ class EditTest(TestBase):
             % (EditTest.cfg.config_args["here"], EditTest.b)
         )
 
-        with mock.patch("alembic.util.edit") as edit:
+        with mock.patch("alembic.util.open_in_editor") as edit:
             command.edit(self.cfg, self.b[0:3])
             edit.assert_called_with(expected_call_arg)
 
-    @testing_config.requirements.editor_installed
-    @testing.emits_python_deprecation_warning("the imp module is deprecated")
-    def test_edit_with_missing_editor(self):
-        with mock.patch("editor.edit") as edit_mock:
-            edit_mock.side_effect = OSError("file not found")
-            assert_raises_message(
-                util.CommandError,
-                "file not found",
-                util.edit,
-                "/not/a/file.txt",
-            )
-
     def test_edit_no_revs(self):
         assert_raises_message(
             util.CommandError,
@@ -975,7 +961,7 @@ class EditTest(TestBase):
         )
 
         command.stamp(self.cfg, self.b)
-        with mock.patch("alembic.util.edit") as edit:
+        with mock.patch("alembic.util.open_in_editor") as edit:
             command.edit(self.cfg, "current")
             edit.assert_called_with(expected_call_arg)
 
diff --git a/tests/test_editor.py b/tests/test_editor.py
new file mode 100644
index 0000000..0ec6f5f
--- /dev/null
+++ b/tests/test_editor.py
@@ -0,0 +1,106 @@
+import os
+from os.path import join
+from unittest.mock import patch
+
+from alembic import util
+from alembic.testing import combinations
+from alembic.testing import expect_raises_message
+from alembic.testing.fixtures import TestBase
+
+
+class TestHelpers(TestBase):
+    def common(self, cb, is_posix=True):
+        with patch("alembic.util.editor.check_call") as check_call, patch(
+            "alembic.util.editor.exists"
+        ) as exists, patch(
+            "alembic.util.editor.is_posix",
+            new=is_posix,
+        ), patch(
+            "os.pathsep", new=":" if is_posix else ";"
+        ):
+            cb(check_call, exists)
+
+    @combinations((True,), (False,))
+    def test_edit_with_user_editor(self, posix):
+        def go(check_call, exists):
+            test_environ = {"EDITOR": "myvim", "PATH": "/usr/bin"}
+            executable = join("/usr/bin", "myvim")
+            if not posix:
+                executable += ".exe"
+
+            exists.side_effect = lambda fname: fname == executable
+            util.open_in_editor("myfile", test_environ)
+            check_call.assert_called_with([executable, "myfile"])
+
+        self.common(go, posix)
+
+    @combinations(("EDITOR",), ("VISUAL",))
+    def test_edit_with_user_editor_exists(self, key):
+        def go(check_call, exists):
+            test_environ = {key: "myvim", "PATH": "/usr/bin"}
+            exists.side_effect = lambda fname: fname == "myvim"
+            util.open_in_editor("myfile", test_environ)
+            check_call.assert_called_with(["myvim", "myfile"])
+
+        self.common(go)
+
+    @combinations((True,), (False,))
+    def test_edit_with_user_editor_precedence(self, with_path):
+        def go(check_call, exists):
+            test_environ = {
+                "EDITOR": "myvim",
+                "VISUAL": "myvisual",
+                "PATH": "/usr/bin",
+            }
+            exes = ["myvim", "myvisual"]
+            if with_path:
+                exes = [join("/usr/bin", n) for n in exes]
+            exists.side_effect = lambda fname: fname in exes
+            util.open_in_editor("myfile", test_environ)
+            check_call.assert_called_with([exes[0], "myfile"])
+
+        self.common(go)
+
+    def test_edit_with_user_editor_abs(self):
+        def go(check_call, exists):
+            test_environ = {"EDITOR": "/foo/myvim", "PATH": "/usr/bin"}
+            exists.side_effect = lambda fname: fname == "/usr/bin/foo/myvim"
+            with expect_raises_message(util.CommandError, "EDITOR"):
+                util.open_in_editor("myfile", test_environ)
+
+        self.common(go)
+
+    def test_edit_with_default_editor(self):
+        def go(check_call, exists):
+            test_environ = {"PATH": os.pathsep.join(["/usr/bin", "/bin"])}
+            executable = join("/bin", "vim")
+
+            exists.side_effect = lambda fname: fname == executable
+            util.open_in_editor("myfile", test_environ)
+            check_call.assert_called_with([executable, "myfile"])
+
+        self.common(go)
+
+    def test_edit_with_default_editor_windows(self):
+        def go(check_call, exists):
+            test_environ = {
+                "PATH": os.pathsep.join(
+                    [r"C:\Windows\System32", r"C:\Users\user\bin"]
+                )
+            }
+            executable = join(r"C:\Users\user\bin", "notepad.exe")
+
+            exists.side_effect = lambda fname: fname == executable
+            util.open_in_editor("myfile", test_environ)
+            check_call.assert_called_with([executable, "myfile"])
+
+        self.common(go, False)
+
+    def test_edit_with_missing_editor(self):
+        def go(check_call, exists):
+            test_environ = {}
+            exists.return_value = False
+            with expect_raises_message(util.CommandError, "EDITOR"):
+                util.open_in_editor("myfile", test_environ)
+
+        self.common(go)
diff --git a/tests/test_script_production.py b/tests/test_script_production.py
index 15d9366..2edae26 100644
--- a/tests/test_script_production.py
+++ b/tests/test_script_production.py
@@ -15,6 +15,7 @@ from alembic.script import ScriptDirectory
 from alembic.testing import assert_raises_message
 from alembic.testing import assertions
 from alembic.testing import eq_
+from alembic.testing import expect_raises_message
 from alembic.testing import is_
 from alembic.testing import mock
 from alembic.testing import ne_
@@ -34,6 +35,10 @@ from alembic.testing.env import write_script
 from alembic.testing.fixtures import TestBase
 from alembic.util import CommandError
 
+try:
+    from unittest.mock import patch
+except ImportError:
+    from mock import patch  # noqa
 env, abc, def_ = None, None, None
 
 
@@ -250,6 +255,17 @@ class ScriptNamingTest(TestBase):
             datetime.datetime(2012, 7, 25, 15, 8, 5),
         )
 
+    def test_no_dateutil_module(self):
+        with patch("alembic.script.base.tz", new=None):
+            with expect_raises_message(
+                CommandError, "The library 'python-dateutil' is required"
+            ):
+                self._test_tz(
+                    "utc",
+                    datetime.datetime(2012, 7, 25, 15, 8, 5),
+                    datetime.datetime(2012, 7, 25, 15, 8, 5),
+                )
+
 
 class RevisionCommandTest(TestBase):
     def setUp(self):