bpo-40503: PEP 615: Tests and implementation for zoneinfo (GH-19909)

This is the initial implementation of PEP 615, the zoneinfo module,
ported from the standalone reference implementation (see
https://www.python.org/dev/peps/pep-0615/#reference-implementation for a
link, which has a more detailed commit history).

This includes (hopefully) all functional elements described in the PEP,
but documentation is found in a separate PR. This includes:

1. A pure python implementation of the ZoneInfo class
2. A C accelerated implementation of the ZoneInfo class
3. Tests with 100% branch coverage for the Python code (though C code
   coverage is less than 100%).
4. A compile-time configuration option on Linux (though not on Windows)

Differences from the reference implementation:

- The module is arranged slightly differently: the accelerated module is
  `_zoneinfo` rather than `zoneinfo._czoneinfo`, which also necessitates
  some changes in the test support function. (Suggested by Victor
  Stinner and Steve Dower.)
- The tests are arranged slightly differently and do not include the
  property tests. The tests live at test/test_zoneinfo/test_zoneinfo.py
  rather than test/test_zoneinfo.py or test/test_zoneinfo/__init__.py
  because we may do some refactoring in the future that would likely
  require this separation anyway; we may:
        - include the property tests
        - automatically run all the tests against both pure Python and C,
          rather than manually constructing C and Python test classes (similar
          to the way this works with test_datetime.py, which generates C
          and Python test cases from datetimetester.py).
- This includes a compile-time configuration option on Linux (though not
  on Windows); added with much help from Thomas Wouters.
- Integration into the CPython build system is obviously different from
  building a standalone zoneinfo module wheel.
- This includes configuration to install the tzdata package as part of
  CI, though only on the coverage jobs. Introducing a PyPI dependency as
  part of the CI build was controversial, and this is seen as less of a
  major change, since the coverage jobs already depend on pip and PyPI.

Additional changes that were introduced as part of this PR, most / all of
which were backported to the reference implementation:

- Fixed reference and memory leaks

    With much debugging help from Pablo Galindo

- Added smoke tests ensuring that the C and Python modules are built

    The import machinery can be somewhat fragile, and the "seamlessly falls
    back to pure Python" nature of this module makes it so that a problem
    building the C extension or a failure to import the pure Python version
    might easily go unnoticed.

- Adjustments to zoneinfo.__dir__

    Suggested by Petr Viktorin.

- Slight refactorings as suggested by Steve Dower.

- Removed unnecessary if check on std_abbr

    Discovered this because of a missing line in branch coverage.

6 files changed, 137 insertions, 1 deletions

diff --git a/PCbuild/_zoneinfo.vcxproj b/PCbuild/_zoneinfo.vcxproj
new file mode 100644
index 0000000..6e6389c
--- /dev/null
+++ b/PCbuild/_zoneinfo.vcxproj
@@ -0,0 +1,109 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|ARM">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|Win32">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|x64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|Win32">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|x64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM">
+      <Configuration>Release</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>{FCBE1EF2-E0F0-40B1-88B5-00A35D378742}</ProjectGuid>
+    <RootNamespace>_zoneinfo</RootNamespace>
+    <Keyword>Win32Proj</Keyword>
+  </PropertyGroup>
+  <Import Project="python.props" />
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <PropertyGroup>
+    <TargetExt>.pyd</TargetExt>
+  </PropertyGroup>
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyproject.props" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <_ProjectFileVersion>10.0.30319.1</_ProjectFileVersion>
+  </PropertyGroup>
+  <ItemGroup>
+    <ClCompile Include="..\Modules\_zoneinfo.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ResourceCompile Include="..\PC\python_nt.rc" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="pythoncore.vcxproj">
+      <Project>{cf7ac3d1-e2df-41d2-bea6-1e2556cdea26}</Project>
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>
diff --git a/PCbuild/_zoneinfo.vcxproj.filters b/PCbuild/_zoneinfo.vcxproj.filters
new file mode 100644
index 0000000..e3c3ef4
--- /dev/null
+++ b/PCbuild/_zoneinfo.vcxproj.filters
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <ResourceCompile Include="..\PC\python_nt.rc" />
+  </ItemGroup>
+  <ItemGroup>
+    <Filter Include="Source Files">
+      <UniqueIdentifier>{2422278e-eeeb-4241-8182-433e2bc5a7fc}</UniqueIdentifier>
+    </Filter>
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="..\Modules\_zoneinfo.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+</Project>
diff --git a/PCbuild/lib.pyproj b/PCbuild/lib.pyproj
index ee01d10..7ce88e5 100644
--- a/PCbuild/lib.pyproj
+++ b/PCbuild/lib.pyproj
@@ -1396,6 +1396,10 @@
     <Compile Include="test\test_zipimport.py" />
     <Compile Include="test\test_zipimport_support.py" />
     <Compile Include="test\test_zlib.py" />
+    <Compile Include="test\test_zoneinfo\__init__.py" />
+    <Compile Include="test\test_zoneinfo\__main__.py" />
+    <Compile Include="test\test_zoneinfo\_support.py" />
+    <Compile Include="test\test_zoneinfo\test_zoneinfo.py" />
     <Compile Include="test\test__locale.py" />
     <Compile Include="test\test__opcode.py" />
     <Compile Include="test\test__osx_support.py" />
@@ -1563,6 +1567,10 @@
     <Compile Include="xml\__init__.py" />
     <Compile Include="zipapp.py" />
     <Compile Include="zipfile.py" />
+    <Compile Include="zoneinfo\_common.py" />
+    <Compile Include="zoneinfo\__init__.py" />
+    <Compile Include="zoneinfo\_tzpath.py" />
+    <Compile Include="zoneinfo\_zoneinfo.py" />
     <Compile Include="_bootlocale.py" />
     <Compile Include="_collections_abc.py" />
     <Compile Include="_compat_pickle.py" />
diff --git a/PCbuild/pcbuild.proj b/PCbuild/pcbuild.proj
index 9c4d352..4d416c5 100644
--- a/PCbuild/pcbuild.proj
+++ b/PCbuild/pcbuild.proj
@@ -51,7 +51,7 @@
     <!-- pyshellext.dll -->
     <Projects Include="pyshellext.vcxproj" />
     <!-- Extension modules -->
-    <ExtensionModules Include="_asyncio;_decimal;_elementtree;_msi;_multiprocessing;_overlapped;pyexpat;_queue;select;unicodedata;winsound;_uuid" />
+    <ExtensionModules Include="_asyncio;_zoneinfo;_decimal;_elementtree;_msi;_multiprocessing;_overlapped;pyexpat;_queue;select;unicodedata;winsound;_uuid" />
     <ExtensionModules Include="_ctypes" Condition="$(IncludeCTypes)" />
     <!-- Extension modules that require external sources -->
     <ExternalModules Include="_bz2;_lzma;_sqlite3" />
diff --git a/PCbuild/pcbuild.sln b/PCbuild/pcbuild.sln
index 6d4c950..61db4e0 100644
--- a/PCbuild/pcbuild.sln
+++ b/PCbuild/pcbuild.sln
@@ -91,6 +91,8 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_testconsole", "_testconsol
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_asyncio", "_asyncio.vcxproj", "{384C224A-7474-476E-A01B-750EA7DE918C}"
 EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_zoneinfo", "_zoneinfo.vcxproj", "{FCBE1EF2-E0F0-40B1-88B5-00A35D378742}"
+EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "_queue", "_queue.vcxproj", "{78D80A15-BD8C-44E2-B49E-1F05B0A0A687}"
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "liblzma", "liblzma.vcxproj", "{12728250-16EC-4DC6-94D7-E21DD88947F8}"
diff --git a/PCbuild/readme.txt b/PCbuild/readme.txt
index 5fe3e8c..c44910e 100644
--- a/PCbuild/readme.txt
+++ b/PCbuild/readme.txt
@@ -132,6 +132,7 @@ library which are implemented in C; each one builds a DLL (renamed to
 _asyncio
 _ctypes
 _ctypes_test
+_zoneinfo
 _decimal
 _elementtree
 _hashlib