refactor: identifiers in a file (#511)

* refactor: identifiers in a file

* chore: more typing

* refactor: PlatStr -> PlatformName

* refactor: load in file, use importlib.resources

* refactor: change toml structure

* refactor: use common Traversable

* fix: ensure reasonable version of importlib_resources

* style: fix extra line

unit_test/build_ids_test.py

@@ -0,0 +1,28 @@
+import toml
+from toml.encoder import TomlEncoder
+
+from cibuildwheel.util import resources_dir
+
+
+class InlineArrayDictEncoder(TomlEncoder):
+    def dump_sections(self, o: dict, sup: str):
+        if all(isinstance(a, list) for a in o.values()):
+            val = ""
+            for k, v in o.items():
+                inner = ",\n  ".join(self.dump_inline_table(d_i).strip() for d_i in v)
+                val += f"{k} = [\n  {inner},\n]\n"
+            return val, self._dict()
+        else:
+            return super().dump_sections(o, sup)
+
+
+def test_compare_configs():
+    with open(resources_dir / "build-platforms.toml") as f:
+        txt = f.read()
+
+    dict_txt = toml.loads(txt)
+
+    new_txt = toml.dumps(dict_txt, encoder=InlineArrayDictEncoder())
+    print(new_txt)
+
+    assert new_txt == txt