python3-tomli: do not build with python3-flit_core, it introduces a cycle

srcpkgs/python3-tomli/template

@@ -1,20 +1,35 @@
 # Template file for 'python3-tomli'
 pkgname=python3-tomli
 version=1.2.1
-revision=2
-wrksrc="tomli-${version}"
+revision=3
+create_wrksrc=yes
+build_wrksrc="tomli-${version}"
 build_style=python3-pep517
-hostmakedepends="python3-flit_core"
+hostmakedepends="python3"
 depends="python3"
 short_desc="Little TOML parser for Python"
 maintainer="Andrew J. Hesford <ajh@sideband.org>"
 license="MIT"
 homepage="https://github.com/hukkin/tomli"
-distfiles="${PYPI_SITE}/t/tomli/tomli-${version}.tar.gz"
-checksum=a5b75cb6f3968abb47af1b40c1819dc519ea82bcc065776a866e8d74c5ca9442
+# flit_core>=3.4.0 requires tomli to run, while tomli requires flit_core to
+# build. Both upstreams are aware of the cycle, but neither cares:
+#     https://github.com/hukkin/tomli/issues/130
+#     https://github.com/takluyver/flit/issues/451
+# As a result, we can't use python3-flit_core to build this package, so we have
+# to just fetch the flit_core tarball to bootstrap tomli. Sigh.
+_flit_version=3.4.0
+distfiles="${PYPI_SITE}/t/tomli/tomli-${version}.tar.gz
+ ${PYPI_SITE}/f/flit_core/flit_core-${_flit_version}.tar.gz"
+checksum="a5b75cb6f3968abb47af1b40c1819dc519ea82bcc065776a866e8d74c5ca9442
+ 29468fa2330969167d1f5c23eb9c0661cb6dacfcd46f361a274609a7f4197530"
 # Archive includes no tests
 make_check=no
 
+pre_build() {
+	# Build requires that tomli be able to import flit_core *and* itself!
+	export PYTHONPATH="${PWD}:${wrksrc}/flit_core-${_flit_version}"
+}
+
 post_install() {
 	vlicense LICENSE
 }