Merge pull request #28 from gocept/preferences-update-lockfile

Update lockfile with preferences

src/appenv.py

@@ -125,6 +125,57 @@ def ensure_venv(target):
         target=target))
 
 
+def ensure_minimal_python():
+    current_python = os.path.realpath(sys.executable)
+    preferences = None
+    if os.path.exists('requirements.txt'):
+        with open('requirements.txt') as f:
+            for line in f:
+                # Expected format:
+                # # appenv-python-preference: 3.1,3.9,3.4
+                if not line.startswith("# appenv-python-preference: "):
+                    continue
+                preferences = line.split(':')[1]
+                preferences = [x.strip() for x in preferences.split(',')]
+                preferences = list(filter(None, preferences))
+                break
+    if not preferences:
+        # We have no preferences defined, use the current python.
+        print("Update lockfile with with {}.".format(current_python))
+        print("If you want to use a different version, set it as via")
+        print(" `# appenv-python-preference:` in requirements.txt.")
+        return
+
+    preferences.sort(key=lambda s: [int(u) for u in s.split('.')])
+
+    for version in preferences[0:1]:
+        python = shutil.which("python{}".format(version))
+        if not python:
+            # not a usable python
+            continue
+        python = os.path.realpath(python)
+        if python == current_python:
+            # found a preferred python and we're already running as it
+            break
+        # Try whether this Python works
+        try:
+            subprocess.check_call([python, "-c", "print(1)"],
+                                  stdout=subprocess.DEVNULL,
+                                  stderr=subprocess.DEVNULL)
+        except subprocess.CalledProcessError:
+            continue
+
+        argv = [os.path.basename(python)] + sys.argv
+        os.environ["APPENV_BEST_PYTHON"] = python
+        os.execv(python, argv)
+    else:
+        print("Could not find the minimal preferred Python version.")
+        print("To ensure a working requirements.lock on all Python versions")
+        print("make Python {} available on this system.".format(
+            preferences[0]))
+        sys.exit(66)
+
+
 def ensure_best_python():
     if "APPENV_BEST_PYTHON" in os.environ:
         # Don't do this twice to avoid being surprised with
@@ -354,6 +405,7 @@ def reset(self, args=None, remaining=None):
         cmd("rm -rf {appenvdir}".format(appenvdir=self.appenv_dir))
 
     def update_lockfile(self, args=None, remaining=None):
+        ensure_minimal_python()
         os.chdir(self.base)
         print("Updating lockfile")
         tmpdir = os.path.join(self.appenv_dir, "updatelock")
@@ -393,6 +445,9 @@ def update_lockfile(self, args=None, remaining=None):
                 if line.strip().startswith('-e '):
                     extra_specs.append(line.strip())
                     continue
+                # filter comments, in particular # appenv-python-preferences
+                if line.strip().startswith('#'):
+                    continue
                 spec = list(pkg_resources.parse_requirements(line))[0]
                 requested_versions[spec.project_name] = spec
 

tests/test_update_lockfile.py

@@ -1,7 +1,10 @@
+import appenv
 import io
+import unittest.mock
 import os
-
-import appenv
+import pytest
+import shutil
+import sys
 
 
 def test_init_and_create_lockfile(workdir, monkeypatch):
@@ -21,3 +24,65 @@ def test_init_and_create_lockfile(workdir, monkeypatch):
     assert (lockfile_content == """\
 ducker==2.0.1
 """)
+
+
+@pytest.mark.skipif(
+    sys.version_info[0:2] != (3, 6), reason='Isolated CI builds')
+def test_update_lockfile_minimal_python(workdir, monkeypatch):
+    """It uses the minimal python version even if it is not best python."""
+    monkeypatch.setattr('sys.stdin',
+                        io.StringIO('pytest\npytest==6.1.2\nppytest\n'))
+
+    env = appenv.AppEnv(os.path.join(workdir, 'ppytest'))
+    env.init()
+
+    lockfile = os.path.join(workdir, "ppytest", "requirements.lock")
+    requirements_file = os.path.join(workdir, "ppytest", "requirements.txt")
+
+    with open(requirements_file, "r+") as f:
+        lines = f.readlines()
+        lines.insert(0, "# appenv-python-preference: 3.8,3.6,3.9\n")
+        f.seek(0)
+        f.writelines(lines)
+
+    env.update_lockfile()
+
+    assert os.path.exists(lockfile)
+    with open(lockfile) as f:
+        lockfile_content = f.read()
+    assert "pytest==6.1.2" in lockfile_content
+    assert "importlib-metadata==" in lockfile_content
+    assert "typing-extensions==" in lockfile_content
+
+
+@pytest.mark.skipif(
+    sys.version_info[0:2] < (3, 8), reason='Isolated CI builds')
+def test_update_lockfile_missing_minimal_python(workdir, monkeypatch):
+    """It raises an error if the minimal python is not available."""
+    monkeypatch.setattr('sys.stdin',
+                        io.StringIO('pytest\npytest==6.1.2\nppytest\n'))
+
+    env = appenv.AppEnv(os.path.join(workdir, 'ppytest'))
+    env.init()
+
+    requirements_file = os.path.join(workdir, "ppytest", "requirements.txt")
+
+    with open(requirements_file, "r+") as f:
+        lines = f.readlines()
+        lines[0] = "# appenv-python-preference: 3.8,3.6,3.9\n"
+        f.seek(0)
+        f.writelines(lines)
+
+    old_which = shutil.which
+
+    def new_which(string):
+        if string == "python3.6":
+            return None
+        else:
+            return old_which(string)
+
+    with unittest.mock.patch('shutil.which') as which:
+        which.side_effect = new_which
+        with pytest.raises(SystemExit) as e:
+            env.update_lockfile()
+    assert e.value.code == 66