Fix the python patch version retrieval when passing an executable

poetry/utils/env.py

@@ -494,18 +494,19 @@ def create_venv(
         python_patch = ".".join([str(v) for v in sys.version_info[:3]])
         python_minor = ".".join([str(v) for v in sys.version_info[:2]])
         if executable:
-            python_minor = decode(
+            python_patch = decode(
                 subprocess.check_output(
                     " ".join(
                         [
                             executable,
                             "-c",
-                            "\"import sys; print('.'.join([str(s) for s in sys.version_info[:2]]))\"",
+                            "\"import sys; print('.'.join([str(s) for s in sys.version_info[:3]]))\"",
                         ]
                     ),
                     shell=True,
                 ).strip()
             )
+            python_minor = ".".join(python_patch.split(".")[:2])
 
         supported_python = self._poetry.package.python_constraint
         if not supported_python.allows(Version.parse(python_patch)):
@@ -517,7 +518,7 @@ def create_venv(
             # Otherwise, we try to find a compatible Python version.
             if executable:
                 raise NoCompatiblePythonVersionFound(
-                    self._poetry.package.python_versions, python_minor
+                    self._poetry.package.python_versions, python_patch
                 )
 
             io.write_line(

tests/utils/test_env.py

@@ -700,6 +700,45 @@ def test_create_venv_uses_patch_version_to_detect_compatibility(
     )
 
 
+def test_create_venv_uses_patch_version_to_detect_compatibility_with_executable(
+    manager, poetry, config, mocker
+):
+    if "VIRTUAL_ENV" in os.environ:
+        del os.environ["VIRTUAL_ENV"]
+
+    version = Version.parse(".".join(str(c) for c in sys.version_info[:3]))
+    poetry.package.python_versions = "~{}".format(
+        ".".join(str(c) for c in (version.major, version.minor - 1, 0))
+    )
+    venv_name = manager.generate_env_name("simple-project", str(poetry.file.parent))
+
+    check_output = mocker.patch(
+        "poetry.utils._compat.subprocess.check_output",
+        side_effect=check_output_wrapper(
+            Version.parse("{}.{}.0".format(version.major, version.minor - 1))
+        ),
+    )
+    m = mocker.patch(
+        "poetry.utils.env.EnvManager.build_venv", side_effect=lambda *args, **kwargs: ""
+    )
+
+    manager.create_venv(
+        NullIO(), executable="python{}.{}".format(version.major, version.minor - 1)
+    )
+
+    assert check_output.called
+    m.assert_called_with(
+        str(
+            Path(
+                "/foo/virtualenvs/{}-py{}.{}".format(
+                    venv_name, version.major, version.minor - 1
+                )
+            )
+        ),
+        executable="python{}.{}".format(version.major, version.minor - 1),
+    )
+
+
 def test_activate_with_in_project_setting_does_not_fail_if_no_venvs_dir(
     manager, poetry, config, tmp_dir, mocker
 ):