Rollup merge of #109267 - jyn514:test-configure, r=Mark-Simulacrum

Add tests for configure.py

I highly recommend reviewing this with whitespace disabled.

Notably, verifying that we generate valid toml relies on python 3.11 so
we can use `tomllib`, so this also switches`x86_64-gnu-llvm-14` (one of the PR builders) to use 3.11.

While fixing that, I noticed that we stopped testing python2.7 support on PR CI in #106085. `@fee1-dead` `@pietroalbini` please be more careful in the future, there is no CI for CI itself that verifies we are testing everything we should be.

- Separate out functions so that each unit test doesn't create a file on disk
- Add a few unit tests

Author: matthiaskrgr

src/bootstrap/bootstrap_test.py

@@ -11,6 +11,7 @@
 from shutil import rmtree
 
 import bootstrap
+import configure
 
 
 class VerifyTestCase(unittest.TestCase):
@@ -74,12 +75,50 @@ def test_same_dates(self):
         self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
 
+class GenerateAndParseConfig(unittest.TestCase):
+    """Test that we can serialize and deserialize a config.toml file"""
+    def serialize_and_parse(self, args):
+        from io import StringIO
+
+        section_order, sections, targets = configure.parse_args(args)
+        buffer = StringIO()
+        configure.write_config_toml(buffer, section_order, targets, sections)
+        build = bootstrap.RustBuild()
+        build.config_toml = buffer.getvalue()
+
+        try:
+            import tomllib
+            # Verify this is actually valid TOML.
+            tomllib.loads(build.config_toml)
+        except ImportError:
+            print("warning: skipping TOML validation, need at least python 3.11", file=sys.stderr)
+        return build
+
+    def test_no_args(self):
+        build = self.serialize_and_parse([])
+        self.assertEqual(build.get_toml("changelog-seen"), '2')
+        self.assertIsNone(build.get_toml("llvm.download-ci-llvm"))
+
+    def test_set_section(self):
+        build = self.serialize_and_parse(["--set", "llvm.download-ci-llvm"])
+        self.assertEqual(build.get_toml("download-ci-llvm", section="llvm"), 'true')
+
+    def test_set_target(self):
+        build = self.serialize_and_parse(["--set", "target.x86_64-unknown-linux-gnu.cc=gcc"])
+        self.assertEqual(build.get_toml("cc", section="target.x86_64-unknown-linux-gnu"), 'gcc')
+
+    # Uncomment when #108928 is fixed.
+    # def test_set_top_level(self):
+    #     build = self.serialize_and_parse(["--set", "profile=compiler"])
+    #     self.assertEqual(build.get_toml("profile"), 'compiler')
+
 if __name__ == '__main__':
     SUITE = unittest.TestSuite()
     TEST_LOADER = unittest.TestLoader()
     SUITE.addTest(doctest.DocTestSuite(bootstrap))
     SUITE.addTests([
         TEST_LOADER.loadTestsFromTestCase(VerifyTestCase),
+        TEST_LOADER.loadTestsFromTestCase(GenerateAndParseConfig),
         TEST_LOADER.loadTestsFromTestCase(ProgramOutOfDate)])
 
     RUNNER = unittest.TextTestRunner(stream=sys.stdout, verbosity=2)