Implement pypi simulator

The pypi simulator is used to simulate the interactions between our code
and the real pypi.

Addresses are mocked, and for the moment it only simulates requests in
https://pypi.org/pypi/<YOUR PACKAGE>/json format.

Test json metadata must be downloaded in advance and placed in
tests/tests_e3/pypi_data/json.

Related to AdaCore#671

tests/tests_e3/conftest.py

@@ -1,7 +1,13 @@
 # type: ignore
+from __future__ import annotations
+
 import os
+from os.path import abspath, dirname, join as path_join, isfile
 import tempfile
 import yaml
+from json import loads as json_loads
+from typing import TYPE_CHECKING
+from re import compile as regex_compile
 
 from e3.env import Env
 from e3.fs import rm
@@ -10,6 +16,9 @@
 
 import pytest
 
+if TYPE_CHECKING:
+    from typing import Any
+
 # When the variable RESULTS_DIR is set to
 # an existing directory, the testsuite will
 # generate results file in "anod" format
@@ -164,3 +173,54 @@ def pytest_sessionfinish(session, exitstatus):
         # pytest docs, which is the closest thing to having an actual Python error in
         # test code.
         session.exitstatus = 3
+
+
+class PypiResponse:
+    def __init__(self, text: str, status_code: int) -> None:
+        self.text = text
+        self.status_code = status_code
+
+    def json(self) -> Any:
+        return json_loads(self.text)
+
+
+class PypiSimulator:
+    PYPI_URL = "https://pypi.org"
+    MATCHER = regex_compile(f"{PYPI_URL}/pypi/(?P<package>.*)/json")
+    DATA_DIR = path_join(dirname(abspath(__file__)), "pypi_data")
+
+    def __init__(self, requests_mock: Any) -> None:
+        self.requests_mock = requests_mock
+        self.requests_mock.stop()
+
+    @classmethod
+    def get_metadata(cls, *args: Any, **kwargs: Any) -> str:
+        m = cls.MATCHER.match(args[0])
+        if not m:
+            raise ValueError("mocked pypi received an unexpected request")
+        package = m.group("package")
+        path = path_join(cls.DATA_DIR, "json", f"{package}.json")
+        if not isfile(path):
+            return PypiResponse('{"message": "Not Found"}', 404)
+
+        try:
+            with open(path) as json_file:
+                text = json_file.read()
+        except Exception:
+            return PypiResponse('{"message": "Internal server error"}', 500)
+
+        return PypiResponse(text, 200)
+
+    def __enter__(self):
+        self.requests_mock.start()
+        self.requests_mock.get(self.MATCHER, json=self.get_metadata)
+        return self
+
+    def __exit__(self, type_t: Any, value: Any, traceback: Any):
+        self.requests_mock.stop()
+
+
+@pytest.fixture(scope="function")
+def pypi_server(requests_mock):
+    requests_mock.stop()
+    return PypiSimulator(requests_mock)

tests/tests_e3/python/main_test.py

@@ -149,3 +149,9 @@ def test_star_requirements():
         pypi.add_wheel(wheel3.path)
         pypi.add_requirement("src2==1.0.0")
         assert len(pypi.closure()) == 2
+
+
+def test_yanked(pypi_server):
+    with pypi_server:
+        print("OK")
+    raise AssertionError("Expected")

tox.ini

@@ -7,6 +7,7 @@ deps =
      ptyprocess;platform_system == "Linux"
      cov: pytest-cov
      cov: coverage
+     requests-mock
 
 passenv = CI,GITHUB_*,CODECOV_*
 extras =