Only require toml for projects with pyproject.toml

Pros:

 - projects without pyproject.toml will have 1 less dependency
 - toml will be buildable with pyproject-rpm-macros out of the box
 - easier bootstrap sequence (in theory)

Cons:

 - projects with pyproject.toml will have 1 more %generate_buildrequires round

macros.pyproject

@@ -74,7 +74,6 @@ fi
 echo 'python%{python3_pkgversion}-devel'
 echo 'python%{python3_pkgversion}dist(pip) >= 19'
 echo 'python%{python3_pkgversion}dist(packaging)'
-echo 'python%{python3_pkgversion}dist(toml)'
 # The first part is for cases when %%{python3_version_nodots} is not yet available
 if [ ! -z "%{?python3_version_nodots}" ] && [ %{python3_version_nodots} -lt 38 ]; then
   echo 'python%{python3_pkgversion}dist(importlib-metadata)'

pyproject-rpm-macros.spec

@@ -90,6 +90,7 @@ export HOSTNAME="rpmbuild"  # to speedup tox in network-less mock, see rhbz#1856
 %changelog
 * Fri Sep 4 2020 Miro Hrončok <miro@hroncok.cz> - 0-27
 - Make code in $PWD importable from %%pyproject_buildrequires
+- Only require toml for projects with pyproject.toml
 
 * Mon Aug 24 2020 Tomas Hrnciar <thrnciar@redhat.com> - 0-26
 - Implement automatic detection of %%lang files in %%pyproject_save_files

pyproject_buildrequires.py

@@ -23,7 +23,6 @@ class EndPass(Exception):
 
 
 try:
-    import toml
     from packaging.requirements import Requirement, InvalidRequirement
     from packaging.utils import canonicalize_name, canonicalize_version
     try:
@@ -154,6 +153,10 @@ def get_backend(requirements):
     except FileNotFoundError:
         pyproject_data = {}
     else:
+        # lazy import toml here, not needed without pyproject.toml
+        requirements.add('toml', source='parsing pyproject.toml')
+        requirements.check(source='parsing pyproject.toml')
+        import toml
         with f:
             pyproject_data = toml.load(f)
 

pyproject_buildrequires_testcases.yaml

@@ -12,22 +12,23 @@ Nothing installed yet:
   pyproject.toml: |
     # empty
   expected: |
-    python3dist(setuptools) >= 40.8
-    python3dist(wheel)
+    python3dist(toml)
   result: 0
 
 Insufficient version of setuptools:
   installed:
     setuptools: 5
     wheel: 1
+    toml: 1
   pyproject.toml: |
     # empty
   expected: |
+    python3dist(toml)
     python3dist(setuptools) >= 40.8
     python3dist(wheel)
   result: 0
 
-Empty pyproject.toml, empty setup.py:
+No pyproject.toml, empty setup.py:
   installed:
     setuptools: 50
     wheel: 1
@@ -42,10 +43,12 @@ Default build system, empty setup.py:
   installed:
     setuptools: 50
     wheel: 1
+    toml: 1
   pyproject.toml: |
     # empty
   setup.py: |
   expected: |
+    python3dist(toml)
     python3dist(setuptools) >= 40.8
     python3dist(wheel)
     python3dist(wheel)
@@ -60,7 +63,8 @@ Erroring setup.py:
   result: 77
 
 Bad character in version:
-  installed: {}
+  installed:
+    toml: 1
   pyproject.toml: |
     [build-system]
     requires = ["pkg == 0.$.^.*"]
@@ -71,6 +75,7 @@ Build system dependencies in pyproject.toml with extras:
   installed:
     setuptools: 50
     wheel: 1
+    toml: 1
   pyproject.toml: |
     [build-system]
     requires = [
@@ -88,6 +93,7 @@ Build system dependencies in pyproject.toml with extras:
         "py3 ; python_version > '3.0'",
     ]
   expected: |
+    python3dist(toml)
     python3dist(foo)
     python3dist(bar) > 5
     python3dist(bar[baz]) > 5
@@ -110,6 +116,7 @@ Build system dependencies in pyproject.toml without extras:
   installed:
     setuptools: 50
     wheel: 1
+    toml: 1
   pyproject.toml: |
     [build-system]
     requires = [
@@ -117,6 +124,7 @@ Build system dependencies in pyproject.toml without extras:
         "multi[extras1,extras2] == 6.0",
     ]
   expected: |
+    python3dist(toml)
     python3dist(bar) > 5
     python3dist(multi) == 6
     python3dist(setuptools) >= 40.8