Add support for building with libmpdec

We don't need-need this until 3.16 now, but earlier versions threatened we
would need it as of 3.15 so I thought it more urgent.  We don't force it on, so
only use if already available.

Author: thatch

Dockerfile

@@ -7,7 +7,7 @@ RUN apt-get update && apt-get install -y git htop build-essential \
     gdb lcov patchelf python3-pip python3-venv tcl \
     libexpat1-dev libffi-dev zlib1g-dev libgdbm-dev libgdbm-compat-dev \
     libssl-dev libsqlite3-dev uuid-dev \
-    liblzma-dev libbz2-dev libzstd-dev
+    liblzma-dev libbz2-dev libzstd-dev libmpdec-dev
 
 RUN /usr/bin/python3 -mpip install -U pip setuptools
 

src/portable_python/cpython.py

@@ -8,7 +8,7 @@
 from runez.pyenv import Version
 
 from portable_python import LOG, patch_file, patch_folder, PPG, PythonBuilder
-from portable_python.external.xcpython import Bdb, Bzip2, Gdbm, LibFFI, Openssl, Readline, Sqlite, Uuid, Xz, Zlib, Zstd
+from portable_python.external.xcpython import Bdb, Bzip2, Gdbm, LibFFI, Openssl, Readline, Sqlite, Uuid, Xz, Zlib, Zstd, Mpdec
 from portable_python.external.xtkinter import TkInter
 from portable_python.inspector import LibAutoCorrect, PythonInspector
 
@@ -96,7 +96,7 @@ def build_information(self):
 
     @classmethod
     def candidate_modules(cls):
-        return [LibFFI, Zlib, Zstd, Xz, Bzip2, Readline, Openssl, Sqlite, Bdb, Gdbm, Uuid, TkInter]
+        return [LibFFI, Zlib, Zstd, Xz, Bzip2, Readline, Openssl, Sqlite, Bdb, Gdbm, Uuid, TkInter, Mpdec]
 
     @property
     def url(self):
@@ -184,6 +184,18 @@ def xenv_LIBZSTD_LIBS(self):
         if self.version >= "3.14" and PPG.target.is_macos:
             yield f"{self.deps_lib_dir}/libzstd.a"
 
+    def xenv_LIBMPDEC_CFLAGS(self):
+        if self.version >= "3.14" and PPG.target.is_macos:
+            # Normally ./configure will autodetect using pkg-config, but
+            # this doesn't typically work on Mac (the pkg-config binary is
+            # in homebrew, which we omit from path) so we have to provide
+            # some hints about how to staticly include it.
+            yield f"-I{self.deps}/include"
+
+    def xenv_LIBMPDEC_LIBS(self):
+        if self.version >= "3.14" and PPG.target.is_macos:
+            yield f"{self.deps_lib_dir}/libmpdec.a"
+
     @runez.cached_property
     def prefix_lib_folder(self):
         """Path to <prefix>/lib/pythonM.m folder"""

src/portable_python/external/xcpython.py

@@ -465,3 +465,41 @@ def _do_linux_compile(self):
         # staticly compile this doesn't need a fixup.  I got as far as:
         # "libdir=\\$(executable_path)/../lib")
         self.run_make("install", f"prefix={os.path.abspath(self.deps)}")
+
+class Mpdec(ModuleBuilder):
+    """
+    Prevent falling back to bundled libmpdec (deprecated and scheduled for removal in Python 3.16)
+    """
+
+    m_debian = "!libmpdec-dev"
+    m_telltale = "{include}/mpdecimal.h"
+
+    xenv_CFLAGS = "-fPIC"
+
+    def auto_select_reason(self):
+        if self.setup.python_spec.version >= "3.16":
+            if PPG.target.is_macos:
+                return "Required for 3.16 and up"
+            if not self.resolved_telltale:
+                return "Required for 3.16 and up"
+
+    @property
+    def url(self):
+        return self.cfg_url(self.version) or f"https://www.bytereef.org/software/mpdecimal/releases/mpdecimal-{self.version}.tar.gz"
+
+    @property
+    def version(self):
+        return self.cfg_version("4.0.1")
+
+    def c_configure_args(self):
+        if config_args := self.cfg_configure(self.deps_lib_dir, self.deps_lib64_dir):
+            yield config_args
+
+        else:
+            pass # yield "--static"
+        yield "--disable-cxx"
+
+    def _do_linux_compile(self):
+        self.run_configure("./configure", self.c_configure_args())
+        self.run_make()
+        self.run_make("install")