python: add use_host_python option; use env in shebangs

BUCK

@@ -3,14 +3,12 @@
 
 """Shared tine Python support, and the toolchain Buck2 looks up as `toolchains//`."""
 
-load("@prelude//toolchains:python.bzl", "python_bootstrap_toolchain")
 load("//python:defs.bzl", "python")
 
 # Declared here rather than in a `toolchains` cell of its own: Buck2 forbids nesting a cell inside an
 # external cell, so declaring it here is what lets a consuming project pull tine in as one.
-python_bootstrap_toolchain(
+python.bootstrap_toolchain(
     name = "python_bootstrap",
-    interpreter = read_config("tine", "python_interpreter", "tine//tools:python3"),
     visibility = ["PUBLIC"],
 )
 

bin/tine

@@ -1,4 +1,4 @@
-#!/usr/bin/python3 -SIB
+#!/usr/bin/env -S python3 -SIB
 
 # SPDX-FileCopyrightText: Amutable GmbH <https://amutable.com/>
 # SPDX-License-Identifier: MPL-2.0

python/defs.bzl

@@ -9,6 +9,7 @@ load("@prelude//decls:toolchains_common.bzl", "toolchains_common")
 load("@prelude//python_bootstrap:python_bootstrap.bzl", "PythonBootstrapSources")
 load("@prelude//python_bootstrap:toolchain.bzl", "PythonBootstrapToolchainInfo")
 load("@prelude//test:inject_test_run_info.bzl", "inject_test_run_info")
+load("@prelude//toolchains:python.bzl", "python_bootstrap_toolchain", "system_python_bootstrap_toolchain")
 load("@prelude//utils:selects.bzl", "selects")
 load("//box:defs.bzl", "box")
 
@@ -204,8 +205,20 @@ def _test(
     _python_test(name = name, box = box, srcs = srcs, deps = deps, **kwargs)
     ty_check(name = name + "-ty", srcs = srcs, deps = deps, boxes = selects.apply(box, lambda value: [] if value == None else [value]))
 
+def _bootstrap_toolchain(name: str, **kwargs) -> None:
+    """Declare the bootstrap toolchain on the pinned interpreter, or on the host's `python3` if asked to.
+
+    The pinned interpreter needs a glibc loader at the standard path. A host without one sets
+    `tine.use_host_python = true` in the project's config.
+    """
+    if read_root_config("tine", "use_host_python") == "true":
+        system_python_bootstrap_toolchain(name = name, **kwargs)
+    else:
+        python_bootstrap_toolchain(name = name, interpreter = read_config("tine", "python_interpreter", "tine//tools:python3"), **kwargs)
+
 python = struct(
     binary = _binary,
+    bootstrap_toolchain = _bootstrap_toolchain,
     flat_tree = flat_tree,
     library = _library,
     test = _test,

tools/ci.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # SPDX-FileCopyrightText: Amutable GmbH <https://amutable.com/>
 # SPDX-License-Identifier: MPL-2.0